systemd.exec(5) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | IMPLICIT DEPENDENCIES | PATHS | CREDENTIALS | CAPABILITIES | SECURITY | MANDATORY ACCESS CONTROL | PROCESS PROPERTIES | SCHEDULING | SANDBOXING | SYSTEM CALL FILTERING | ENVIRONMENT | LOGGING AND STANDARD INPUT/OUTPUT | SYSTEM V COMPATIBILITY | ENVIRONMENT VARIABLES IN SPAWNED PROCESSES | PROCESS EXIT CODES | SEE ALSO | NOTES | COLOPHON

SYSTEMD.EXEC(5)                 systemd.exec                 SYSTEMD.EXEC(5)

NAME         top

       systemd.exec - Execution environment configuration

SYNOPSIS         top

       service.service, socket.socket, mount.mount, swap.swap

DESCRIPTION         top

       Unit configuration files for services, sockets, mount points, and
       swap devices share a subset of configuration options which define the
       execution environment of spawned processes.

       This man page lists the configuration options shared by these four
       unit types. See systemd.unit(5) for the common options of all unit
       configuration files, and systemd.service(5), systemd.socket(5),
       systemd.swap(5), and systemd.mount(5) for more information on the
       specific unit configuration files. The execution specific
       configuration options are configured in the [Service], [Socket],
       [Mount], or [Swap] sections, depending on the unit type.

       In addition, options which control resources through Linux Control
       Groups (cgroups) are listed in systemd.resource-control(5). Those
       options complement options listed here.

IMPLICIT DEPENDENCIES         top

       A few execution parameters result in additional, automatic
       dependencies to be added:

       ·   Units with WorkingDirectory=, RootDirectory=, RootImage=,
           RuntimeDirectory=, StateDirectory=, CacheDirectory=,
           LogsDirectory= or ConfigurationDirectory= set automatically gain
           dependencies of type Requires= and After= on all mount units
           required to access the specified paths. This is equivalent to
           having them listed explicitly in RequiresMountsFor=.

       ·   Similar, units with PrivateTmp= enabled automatically get mount
           unit dependencies for all mounts required to access /tmp and
           /var/tmp. They will also gain an automatic After= dependency on
           systemd-tmpfiles-setup.service(8).

       ·   Units whose standard output or error output is connected to
           journal or kmsg (or their combinations with console output, see
           below) automatically acquire dependencies of type After= on
           systemd-journald.socket.

       ·   Units using LogNamespace= will automatically gain ordering and
           requirement dependencies on the two socket units associated with
           systemd-journald@.service instances.

PATHS         top

       The following settings may be used to change a service's view of the
       filesystem. Please note that the paths must be absolute and must not
       contain a ".."  path component.

       WorkingDirectory=
           Takes a directory path relative to the service's root directory
           specified by RootDirectory=, or the special value "~". Sets the
           working directory for executed processes. If set to "~", the home
           directory of the user specified in User= is used. If not set,
           defaults to the root directory when systemd is running as a
           system instance and the respective user's home directory if run
           as user. If the setting is prefixed with the "-" character, a
           missing working directory is not considered fatal. If
           RootDirectory=/RootImage= is not set, then WorkingDirectory= is
           relative to the root of the system running the service manager.
           Note that setting this parameter might result in additional
           dependencies to be added to the unit (see above).

       RootDirectory=
           Takes a directory path relative to the host's root directory
           (i.e. the root of the system running the service manager). Sets
           the root directory for executed processes, with the chroot(2)
           system call. If this is used, it must be ensured that the process
           binary and all its auxiliary files are available in the chroot()
           jail. Note that setting this parameter might result in additional
           dependencies to be added to the unit (see above).

           The MountAPIVFS= and PrivateUsers= settings are particularly
           useful in conjunction with RootDirectory=. For details, see
           below.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       RootImage=
           Takes a path to a block device node or regular file as argument.
           This call is similar to RootDirectory= however mounts a file
           system hierarchy from a block device node or loopback file
           instead of a directory. The device node or file system image file
           needs to contain a file system without a partition table, or a
           file system within an MBR/MS-DOS or GPT partition table with only
           a single Linux-compatible partition, or a set of file systems
           within a GPT partition table that follows the Discoverable
           Partitions Specification[1].

           When DevicePolicy= is set to "closed" or "strict", or set to
           "auto" and DeviceAllow= is set, then this setting adds
           /dev/loop-control with rw mode, "block-loop" and "block-blkext"
           with rwm mode to DeviceAllow=. See systemd.resource-control(5)
           for the details about DevicePolicy= or DeviceAllow=. Also, see
           PrivateDevices= below, as it may change the setting of
           DevicePolicy=.

           Units making use of RootImage= automatically gain an After=
           dependency on systemd-udevd.service.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       RootImageOptions=
           Takes a comma-separated list of mount options that will be used
           on disk images specified by RootImage=. Optionally a partition
           number can be prefixed, followed by colon, in case the image has
           multiple partitions, otherwise partition number 0 is implied.
           Options for multiple partitions can be specified in a single line
           with space separators. Assigning an empty string removes previous
           assignments. For a list of valid mount options, please refer to
           mount(8).

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       RootHash=
           Takes a data integrity (dm-verity) root hash specified in
           hexadecimal, or the path to a file containing a root hash in
           ASCII hexadecimal format. This option enables data integrity
           checks using dm-verity, if the used image contains the
           appropriate integrity data (see above) or if RootVerity= is used.
           The specified hash must match the root hash of integrity data,
           and is usually at least 256 bits (and hence 64 formatted
           hexadecimal characters) long (in case of SHA256 for example). If
           this option is not specified, but the image file carries the
           "user.verity.roothash" extended file attribute (see xattr(7)),
           then the root hash is read from it, also as formatted hexadecimal
           characters. If the extended file attribute is not found (or is
           not supported by the underlying file system), but a file with the
           .roothash suffix is found next to the image file, bearing
           otherwise the same name (except if the image has the .raw suffix,
           in which case the root hash file must not have it in its name),
           the root hash is read from it and automatically used, also as
           formatted hexadecimal characters.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       RootHashSignature=
           Takes a PKCS7 formatted binary signature of the RootHash= option
           as a path to a DER encoded signature file or as an ASCII base64
           string encoding of the DER encoded signature, prefixed by
           "base64:". The dm-verity volume will only be opened if the
           signature of the root hash signature is valid and created by a
           public key present in the kernel keyring. If this option is not
           specified, but a file with the .roothash.p7s suffix is found next
           to the image file, bearing otherwise the same name (except if the
           image has the .raw suffix, in which case the signature file must
           not have it in its name), the signature is read from it and
           automatically used.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       RootVerity=
           Takes the path to a data integrity (dm-verity) file. This option
           enables data integrity checks using dm-verity, if RootImage= is
           used and a root-hash is passed and if the used image itself does
           not contains the integrity data. The integrity data must be
           matched by the root hash. If this option is not specified, but a
           file with the .verity suffix is found next to the image file,
           bearing otherwise the same name (except if the image has the .raw
           suffix, in which case the verity data file must not have it in
           its name), the verity data is read from it and automatically
           used.

           This option is supported only for disk images that contain a
           single file system, without an enveloping partition table. Images
           that contain a GPT partition table should instead include both
           root file system and matching Verity data in the same image,
           implementing the Discoverable Partition Specification[1].

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       MountAPIVFS=
           Takes a boolean argument. If on, a private mount namespace for
           the unit's processes is created and the API file systems /proc,
           /sys, and /dev are mounted inside of it, unless they are already
           mounted. Note that this option has no effect unless used in
           conjunction with RootDirectory=/RootImage= as these three mounts
           are generally mounted in the host anyway, and unless the root
           directory is changed, the private mount namespace will be a 1:1
           copy of the host's, and include these three mounts. Note that the
           /dev file system of the host is bind mounted if this option is
           used without PrivateDevices=. To run the service with a private,
           minimal version of /dev/, combine this option with
           PrivateDevices=.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       BindPaths=, BindReadOnlyPaths=
           Configures unit-specific bind mounts. A bind mount makes a
           particular file or directory available at an additional place in
           the unit's view of the file system. Any bind mounts created with
           this option are specific to the unit, and are not visible in the
           host's mount table. This option expects a whitespace separated
           list of bind mount definitions. Each definition consists of a
           colon-separated triple of source path, destination path and
           option string, where the latter two are optional. If only a
           source path is specified the source and destination is taken to
           be the same. The option string may be either "rbind" or "norbind"
           for configuring a recursive or non-recursive bind mount. If the
           destination path is omitted, the option string must be omitted
           too. Each bind mount definition may be prefixed with "-", in
           which case it will be ignored when its source path does not
           exist.

           BindPaths= creates regular writable bind mounts (unless the
           source file system mount is already marked read-only), while
           BindReadOnlyPaths= creates read-only bind mounts. These settings
           may be used more than once, each usage appends to the unit's list
           of bind mounts. If the empty string is assigned to either of
           these two options the entire list of bind mounts defined prior to
           this is reset. Note that in this case both read-only and regular
           bind mounts are reset, regardless which of the two settings is
           used.

           This option is particularly useful when RootDirectory=/RootImage=
           is used. In this case the source path refers to a path on the
           host file system, while the destination path refers to a path
           below the root directory of the unit.

           Note that the destination directory must exist or systemd must be
           able to create it. Thus, it is not possible to use those options
           for mount points nested underneath paths specified in
           InaccessiblePaths=, or under /home/ and other protected
           directories if ProtectHome=yes is specified.
           TemporaryFileSystem= with ":ro" or ProtectHome=tmpfs should be
           used instead.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       MountImages=
           This setting is similar to RootImage= in that it mounts a file
           system hierarchy from a block device node or loopback file, but
           the destination directory can be specified as well as mount
           options. This option expects a whitespace separated list of mount
           definitions. Each definition consists of a colon-separated tuple
           of source path and destination directory. Each mount definition
           may be prefixed with "-", in which case it will be ignored when
           its source path does not exist. The source argument is a path to
           a block device node or regular file. If source or destination
           contain a ":", it needs to be escaped as "\:". The device node or
           file system image file needs to follow the same rules as
           specified for RootImage=. Any mounts created with this option are
           specific to the unit, and are not visible in the host's mount
           table.

           These settings may be used more than once, each usage appends to
           the unit's list of mount paths. If the empty string is assigned,
           the entire list of mount paths defined prior to this is reset.

           Note that the destination directory must exist or systemd must be
           able to create it. Thus, it is not possible to use those options
           for mount points nested underneath paths specified in
           InaccessiblePaths=, or under /home/ and other protected
           directories if ProtectHome=yes is specified.

           When DevicePolicy= is set to "closed" or "strict", or set to
           "auto" and DeviceAllow= is set, then this setting adds
           /dev/loop-control with rw mode, "block-loop" and "block-blkext"
           with rwm mode to DeviceAllow=. See systemd.resource-control(5)
           for the details about DevicePolicy= or DeviceAllow=. Also, see
           PrivateDevices= below, as it may change the setting of
           DevicePolicy=.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

CREDENTIALS         top

       These options are only available for system services and are not
       supported for services running in per-user instances of the service
       manager.

       User=, Group=
           Set the UNIX user or group that the processes are executed as,
           respectively. Takes a single user or group name, or a numeric ID
           as argument. For system services (services run by the system
           service manager, i.e. managed by PID 1) and for user services of
           the root user (services managed by root's instance of systemd
           --user), the default is "root", but User= may be used to specify
           a different user. For user services of any other user, switching
           user identity is not permitted, hence the only valid setting is
           the same user the user's service manager is running as. If no
           group is set, the default group of the user is used. This setting
           does not affect commands whose command line is prefixed with "+".

           Note that this enforces only weak restrictions on the user/group
           name syntax, but will generate warnings in many cases where
           user/group names do not adhere to the following rules: the
           specified name should consist only of the characters a-z, A-Z,
           0-9, "_" and "-", except for the first character which must be
           one of a-z, A-Z and "_" (i.e. digits and "-" are not permitted as
           first character). The user/group name must have at least one
           character, and at most 31. These restrictions are made in order
           to avoid ambiguities and to ensure user/group names and unit
           files remain portable among Linux systems. For further details on
           the names accepted and the names warned about see User/Group Name
           Syntax[2].

           When used in conjunction with DynamicUser= the user/group name
           specified is dynamically allocated at the time the service is
           started, and released at the time the service is stopped — unless
           it is already allocated statically (see below). If DynamicUser=
           is not used the specified user and group must have been created
           statically in the user database no later than the moment the
           service is started, for example using the sysusers.d(5) facility,
           which is applied at boot or package install time. If the user
           does not exist by then program invocation will fail.

           If the User= setting is used the supplementary group list is
           initialized from the specified user's default group list, as
           defined in the system's user and group database. Additional
           groups may be configured through the SupplementaryGroups= setting
           (see below).

       DynamicUser=
           Takes a boolean parameter. If set, a UNIX user and group pair is
           allocated dynamically when the unit is started, and released as
           soon as it is stopped. The user and group will not be added to
           /etc/passwd or /etc/group, but are managed transiently during
           runtime. The nss-systemd(8) glibc NSS module provides integration
           of these dynamic users/groups into the system's user and group
           databases. The user and group name to use may be configured via
           User= and Group= (see above). If these options are not used and
           dynamic user/group allocation is enabled for a unit, the name of
           the dynamic user/group is implicitly derived from the unit name.
           If the unit name without the type suffix qualifies as valid user
           name it is used directly, otherwise a name incorporating a hash
           of it is used. If a statically allocated user or group of the
           configured name already exists, it is used and no dynamic
           user/group is allocated. Note that if User= is specified and the
           static group with the name exists, then it is required that the
           static user with the name already exists. Similarly, if Group= is
           specified and the static user with the name exists, then it is
           required that the static group with the name already exists.
           Dynamic users/groups are allocated from the UID/GID range
           61184...65519. It is recommended to avoid this range for regular
           system or login users. At any point in time each UID/GID from
           this range is only assigned to zero or one dynamically allocated
           users/groups in use. However, UID/GIDs are recycled after a unit
           is terminated. Care should be taken that any processes running as
           part of a unit for which dynamic users/groups are enabled do not
           leave files or directories owned by these users/groups around, as
           a different unit might get the same UID/GID assigned later on,
           and thus gain access to these files or directories. If
           DynamicUser= is enabled, RemoveIPC= and PrivateTmp= are implied
           (and cannot be turned off). This ensures that the lifetime of IPC
           objects and temporary files created by the executed processes is
           bound to the runtime of the service, and hence the lifetime of
           the dynamic user/group. Since /tmp/ and /var/tmp/ are usually the
           only world-writable directories on a system this ensures that a
           unit making use of dynamic user/group allocation cannot leave
           files around after unit termination. Furthermore NoNewPrivileges=
           and RestrictSUIDSGID= are implicitly enabled (and cannot be
           disabled), to ensure that processes invoked cannot take benefit
           or create SUID/SGID files or directories. Moreover
           ProtectSystem=strict and ProtectHome=read-only are implied, thus
           prohibiting the service to write to arbitrary file system
           locations. In order to allow the service to write to certain
           directories, they have to be allow-listed using ReadWritePaths=,
           but care must be taken so that UID/GID recycling doesn't create
           security issues involving files created by the service. Use
           RuntimeDirectory= (see below) in order to assign a writable
           runtime directory to a service, owned by the dynamic user/group
           and removed automatically when the unit is terminated. Use
           StateDirectory=, CacheDirectory= and LogsDirectory= in order to
           assign a set of writable directories for specific purposes to the
           service in a way that they are protected from vulnerabilities due
           to UID reuse (see below). If this option is enabled, care should
           be taken that the unit's processes do not get access to
           directories outside of these explicitly configured and managed
           ones. Specifically, do not use BindPaths= and be careful with
           AF_UNIX file descriptor passing for directory file descriptors,
           as this would permit processes to create files or directories
           owned by the dynamic user/group that are not subject to the
           lifecycle and access guarantees of the service. Defaults to off.

       SupplementaryGroups=
           Sets the supplementary Unix groups the processes are executed as.
           This takes a space-separated list of group names or IDs. This
           option may be specified more than once, in which case all listed
           groups are set as supplementary groups. When the empty string is
           assigned, the list of supplementary groups is reset, and all
           assignments prior to this one will have no effect. In any way,
           this option does not override, but extends the list of
           supplementary groups configured in the system group database for
           the user. This does not affect commands prefixed with "+".

       PAMName=
           Sets the PAM service name to set up a session as. If set, the
           executed process will be registered as a PAM session under the
           specified service name. This is only useful in conjunction with
           the User= setting, and is otherwise ignored. If not set, no PAM
           session will be opened for the executed processes. See pam(8) for
           details.

           Note that for each unit making use of this option a PAM session
           handler process will be maintained as part of the unit and stays
           around as long as the unit is active, to ensure that appropriate
           actions can be taken when the unit and hence the PAM session
           terminates. This process is named "(sd-pam)" and is an immediate
           child process of the unit's main process.

           Note that when this option is used for a unit it is very likely
           (depending on PAM configuration) that the main unit process will
           be migrated to its own session scope unit when it is activated.
           This process will hence be associated with two units: the unit it
           was originally started from (and for which PAMName= was
           configured), and the session scope unit. Any child processes of
           that process will however be associated with the session scope
           unit only. This has implications when used in combination with
           NotifyAccess=all, as these child processes will not be able to
           affect changes in the original unit through notification
           messages. These messages will be considered belonging to the
           session scope unit and not the original unit. It is hence not
           recommended to use PAMName= in combination with NotifyAccess=all.

CAPABILITIES         top

       These options are only available for system services and are not
       supported for services running in per-user instances of the service
       manager.

       CapabilityBoundingSet=
           Controls which capabilities to include in the capability bounding
           set for the executed process. See capabilities(7) for details.
           Takes a whitespace-separated list of capability names, e.g.
           CAP_SYS_ADMIN, CAP_DAC_OVERRIDE, CAP_SYS_PTRACE. Capabilities
           listed will be included in the bounding set, all others are
           removed. If the list of capabilities is prefixed with "~", all
           but the listed capabilities will be included, the effect of the
           assignment inverted. Note that this option also affects the
           respective capabilities in the effective, permitted and
           inheritable capability sets. If this option is not used, the
           capability bounding set is not modified on process execution,
           hence no limits on the capabilities of the process are enforced.
           This option may appear more than once, in which case the bounding
           sets are merged by OR, or by AND if the lines are prefixed with
           "~" (see below). If the empty string is assigned to this option,
           the bounding set is reset to the empty capability set, and all
           prior settings have no effect. If set to "~" (without any further
           argument), the bounding set is reset to the full set of available
           capabilities, also undoing any previous settings. This does not
           affect commands prefixed with "+".

           Example: if a unit has the following,

               CapabilityBoundingSet=CAP_A CAP_B
               CapabilityBoundingSet=CAP_B CAP_C

           then CAP_A, CAP_B, and CAP_C are set. If the second line is
           prefixed with "~", e.g.,

               CapabilityBoundingSet=CAP_A CAP_B
               CapabilityBoundingSet=~CAP_B CAP_C

           then, only CAP_A is set.

       AmbientCapabilities=
           Controls which capabilities to include in the ambient capability
           set for the executed process. Takes a whitespace-separated list
           of capability names, e.g.  CAP_SYS_ADMIN, CAP_DAC_OVERRIDE,
           CAP_SYS_PTRACE. This option may appear more than once in which
           case the ambient capability sets are merged (see the above
           examples in CapabilityBoundingSet=). If the list of capabilities
           is prefixed with "~", all but the listed capabilities will be
           included, the effect of the assignment inverted. If the empty
           string is assigned to this option, the ambient capability set is
           reset to the empty capability set, and all prior settings have no
           effect. If set to "~" (without any further argument), the ambient
           capability set is reset to the full set of available
           capabilities, also undoing any previous settings. Note that
           adding capabilities to ambient capability set adds them to the
           process's inherited capability set.

           Ambient capability sets are useful if you want to execute a
           process as a non-privileged user but still want to give it some
           capabilities. Note that in this case option keep-caps is
           automatically added to SecureBits= to retain the capabilities
           over the user change.  AmbientCapabilities= does not affect
           commands prefixed with "+".

SECURITY         top

       NoNewPrivileges=
           Takes a boolean argument. If true, ensures that the service
           process and all its children can never gain new privileges
           through execve() (e.g. via setuid or setgid bits, or filesystem
           capabilities). This is the simplest and most effective way to
           ensure that a process and its children can never elevate
           privileges again. Defaults to false, but certain settings
           override this and ignore the value of this setting. This is the
           case when SystemCallFilter=, SystemCallArchitectures=,
           RestrictAddressFamilies=, RestrictNamespaces=, PrivateDevices=,
           ProtectKernelTunables=, ProtectKernelModules=,
           ProtectKernelLogs=, ProtectClock=, MemoryDenyWriteExecute=,
           RestrictRealtime=, RestrictSUIDSGID=, DynamicUser= or
           LockPersonality= are specified. Note that even if this setting is
           overridden by them, systemctl show shows the original value of
           this setting. Also see No New Privileges Flag[3].

       SecureBits=
           Controls the secure bits set for the executed process. Takes a
           space-separated combination of options from the following list:
           keep-caps, keep-caps-locked, no-setuid-fixup,
           no-setuid-fixup-locked, noroot, and noroot-locked. This option
           may appear more than once, in which case the secure bits are
           ORed. If the empty string is assigned to this option, the bits
           are reset to 0. This does not affect commands prefixed with "+".
           See capabilities(7) for details.

MANDATORY ACCESS CONTROL         top

       These options are only available for system services and are not
       supported for services running in per-user instances of the service
       manager.

       SELinuxContext=
           Set the SELinux security context of the executed process. If set,
           this will override the automated domain transition. However, the
           policy still needs to authorize the transition. This directive is
           ignored if SELinux is disabled. If prefixed by "-", all errors
           will be ignored. This does not affect commands prefixed with "+".
           See setexeccon(3) for details.

       AppArmorProfile=
           Takes a profile name as argument. The process executed by the
           unit will switch to this profile when started. Profiles must
           already be loaded in the kernel, or the unit will fail. If
           prefixed by "-", all errors will be ignored. This setting has no
           effect if AppArmor is not enabled. This setting not affect
           commands prefixed with "+".

       SmackProcessLabel=
           Takes a SMACK64 security label as argument. The process executed
           by the unit will be started under this label and SMACK will
           decide whether the process is allowed to run or not, based on it.
           The process will continue to run under the label specified here
           unless the executable has its own SMACK64EXEC label, in which
           case the process will transition to run under that label. When
           not specified, the label that systemd is running under is used.
           This directive is ignored if SMACK is disabled.

           The value may be prefixed by "-", in which case all errors will
           be ignored. An empty value may be specified to unset previous
           assignments. This does not affect commands prefixed with "+".

PROCESS PROPERTIES         top

       LimitCPU=, LimitFSIZE=, LimitDATA=, LimitSTACK=, LimitCORE=,
       LimitRSS=, LimitNOFILE=, LimitAS=, LimitNPROC=, LimitMEMLOCK=,
       LimitLOCKS=, LimitSIGPENDING=, LimitMSGQUEUE=, LimitNICE=,
       LimitRTPRIO=, LimitRTTIME=
           Set soft and hard limits on various resources for executed
           processes. See setrlimit(2) for details on the resource limit
           concept. Resource limits may be specified in two formats: either
           as single value to set a specific soft and hard limit to the same
           value, or as colon-separated pair soft:hard to set both limits
           individually (e.g.  "LimitAS=4G:16G"). Use the string infinity to
           configure no limit on a specific resource. The multiplicative
           suffixes K, M, G, T, P and E (to the base 1024) may be used for
           resource limits measured in bytes (e.g.  "LimitAS=16G"). For the
           limits referring to time values, the usual time units ms, s, min,
           h and so on may be used (see systemd.time(7) for details). Note
           that if no time unit is specified for LimitCPU= the default unit
           of seconds is implied, while for LimitRTTIME= the default unit of
           microseconds is implied. Also, note that the effective
           granularity of the limits might influence their enforcement. For
           example, time limits specified for LimitCPU= will be rounded up
           implicitly to multiples of 1s. For LimitNICE= the value may be
           specified in two syntaxes: if prefixed with "+" or "-", the value
           is understood as regular Linux nice value in the range -20..19.
           If not prefixed like this the value is understood as raw resource
           limit parameter in the range 0..40 (with 0 being equivalent to
           1).

           Note that most process resource limits configured with these
           options are per-process, and processes may fork in order to
           acquire a new set of resources that are accounted independently
           of the original process, and may thus escape limits set. Also
           note that LimitRSS= is not implemented on Linux, and setting it
           has no effect. Often it is advisable to prefer the resource
           controls listed in systemd.resource-control(5) over these
           per-process limits, as they apply to services as a whole, may be
           altered dynamically at runtime, and are generally more
           expressive. For example, MemoryMax= is a more powerful (and
           working) replacement for LimitRSS=.

           Resource limits not configured explicitly for a unit default to
           the value configured in the various DefaultLimitCPU=,
           DefaultLimitFSIZE=, ... options available in
           systemd-system.conf(5), and – if not configured there – the
           kernel or per-user defaults, as defined by the OS (the latter
           only for user services, see below).

           For system units these resource limits may be chosen freely. When
           these settings are configured in a user service (i.e. a service
           run by the per-user instance of the service manager) they cannot
           be used to raise the limits above those set for the user manager
           itself when it was first invoked, as the user's service manager
           generally lacks the privileges to do so. In user context these
           configuration options are hence only useful to lower the limits
           passed in or to raise the soft limit to the maximum of the hard
           limit as configured for the user. To raise the user's limits
           further, the available configuration mechanisms differ between
           operating systems, but typically require privileges. In most
           cases it is possible to configure higher per-user resource limits
           via PAM or by setting limits on the system service encapsulating
           the user's service manager, i.e. the user's instance of
           user@.service. After making such changes, make sure to restart
           the user's service manager.

           Table 1. Resource limit directives, their equivalent ulimit shell
           commands and the unit used
           ┌─────────────────┬───────────────────┬─────────────────────┐
           │Directive        ulimit equivalent │ Unit                │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitCPU=        │ ulimit -t         │ Seconds             │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitFSIZE=      │ ulimit -f         │ Bytes               │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitDATA=       │ ulimit -d         │ Bytes               │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitSTACK=      │ ulimit -s         │ Bytes               │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitCORE=       │ ulimit -c         │ Bytes               │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitRSS=        │ ulimit -m         │ Bytes               │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitNOFILE=     │ ulimit -n         │ Number of File      │
           │                 │                   │ Descriptors         │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitAS=         │ ulimit -v         │ Bytes               │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitNPROC=      │ ulimit -u         │ Number of Processes │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitMEMLOCK=    │ ulimit -l         │ Bytes               │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitLOCKS=      │ ulimit -x         │ Number of Locks     │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitSIGPENDING= │ ulimit -i         │ Number of Queued    │
           │                 │                   │ Signals             │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitMSGQUEUE=   │ ulimit -q         │ Bytes               │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitNICE=       │ ulimit -e         │ Nice Level          │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitRTPRIO=     │ ulimit -r         │ Realtime Priority   │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitRTTIME=     │ No equivalent     │ Microseconds        │
           └─────────────────┴───────────────────┴─────────────────────┘

       UMask=
           Controls the file mode creation mask. Takes an access mode in
           octal notation. See umask(2) for details. Defaults to 0022 for
           system units. For units of the user service manager the default
           value is inherited from the user instance (whose default is
           inherited from the system service manager, and thus also is
           0022). Hence changing the default value of a user instance,
           either via UMask= or via a PAM module, will affect the user
           instance itself and all user units started by the user instance
           unless a user unit has specified its own UMask=.

       CoredumpFilter=
           Controls which types of memory mappings will be saved if the
           process dumps core (using the /proc/pid/coredump_filter file).
           Takes a whitespace-separated combination of mapping type names or
           numbers (with the default base 16). Mapping type names are
           private-anonymous, shared-anonymous, private-file-backed,
           shared-file-backed, elf-headers, private-huge, shared-huge,
           private-dax, shared-dax, and the special values all (all types)
           and default (the kernel default of "private-anonymous
           shared-anonymous elf-headers private-huge"). See core(5) for the
           meaning of the mapping types. When specified multiple times, all
           specified masks are ORed. When not set, or if the empty value is
           assigned, the inherited value is not changed.

           Example 1. Add DAX pages to the dump filter

               CoredumpFilter=default private-dax shared-dax

       KeyringMode=
           Controls how the kernel session keyring is set up for the service
           (see session-keyring(7) for details on the session keyring).
           Takes one of inherit, private, shared. If set to inherit no
           special keyring setup is done, and the kernel's default behaviour
           is applied. If private is used a new session keyring is allocated
           when a service process is invoked, and it is not linked up with
           any user keyring. This is the recommended setting for system
           services, as this ensures that multiple services running under
           the same system user ID (in particular the root user) do not
           share their key material among each other. If shared is used a
           new session keyring is allocated as for private, but the user
           keyring of the user configured with User= is linked into it, so
           that keys assigned to the user may be requested by the unit's
           processes. In this modes multiple units running processes under
           the same user ID may share key material. Unless inherit is
           selected the unique invocation ID for the unit (see below) is
           added as a protected key by the name "invocation_id" to the newly
           created session keyring. Defaults to private for services of the
           system service manager and to inherit for non-service units and
           for services of the user service manager.

       OOMScoreAdjust=
           Sets the adjustment value for the Linux kernel's Out-Of-Memory
           (OOM) killer score for executed processes. Takes an integer
           between -1000 (to disable OOM killing of processes of this unit)
           and 1000 (to make killing of processes of this unit under memory
           pressure very likely). See proc.txt[4] for details. If not
           specified defaults to the OOM score adjustment level of the
           service manager itself, which is normally at 0.

           Use the OOMPolicy= setting of service units to configure how the
           service manager shall react to the kernel OOM killer terminating
           a process of the service. See systemd.service(5) for details.

       TimerSlackNSec=
           Sets the timer slack in nanoseconds for the executed processes.
           The timer slack controls the accuracy of wake-ups triggered by
           timers. See prctl(2) for more information. Note that in contrast
           to most other time span definitions this parameter takes an
           integer value in nano-seconds if no unit is specified. The usual
           time units are understood too.

       Personality=
           Controls which kernel architecture uname(2) shall report, when
           invoked by unit processes. Takes one of the architecture
           identifiers x86, x86-64, ppc, ppc-le, ppc64, ppc64-le, s390 or
           s390x. Which personality architectures are supported depends on
           the system architecture. Usually the 64bit versions of the
           various system architectures support their immediate 32bit
           personality architecture counterpart, but no others. For example,
           x86-64 systems support the x86-64 and x86 personalities but no
           others. The personality feature is useful when running 32-bit
           services on a 64-bit host system. If not specified, the
           personality is left unmodified and thus reflects the personality
           of the host system's kernel.

       IgnoreSIGPIPE=
           Takes a boolean argument. If true, causes SIGPIPE to be ignored
           in the executed process. Defaults to true because SIGPIPE
           generally is useful only in shell pipelines.

SCHEDULING         top

       Nice=
           Sets the default nice level (scheduling priority) for executed
           processes. Takes an integer between -20 (highest priority) and 19
           (lowest priority). See setpriority(2) for details.

       CPUSchedulingPolicy=
           Sets the CPU scheduling policy for executed processes. Takes one
           of other, batch, idle, fifo or rr. See sched_setscheduler(2) for
           details.

       CPUSchedulingPriority=
           Sets the CPU scheduling priority for executed processes. The
           available priority range depends on the selected CPU scheduling
           policy (see above). For real-time scheduling policies an integer
           between 1 (lowest priority) and 99 (highest priority) can be
           used. See sched_setscheduler(2) for details.

       CPUSchedulingResetOnFork=
           Takes a boolean argument. If true, elevated CPU scheduling
           priorities and policies will be reset when the executed processes
           fork, and can hence not leak into child processes. See
           sched_setscheduler(2) for details. Defaults to false.

       CPUAffinity=
           Controls the CPU affinity of the executed processes. Takes a list
           of CPU indices or ranges separated by either whitespace or
           commas. Alternatively, takes a special "numa" value in which case
           systemd automatically derives allowed CPU range based on the
           value of NUMAMask= option. CPU ranges are specified by the lower
           and upper CPU indices separated by a dash. This option may be
           specified more than once, in which case the specified CPU
           affinity masks are merged. If the empty string is assigned, the
           mask is reset, all assignments prior to this will have no effect.
           See sched_setaffinity(2) for details.

       NUMAPolicy=
           Controls the NUMA memory policy of the executed processes. Takes
           a policy type, one of: default, preferred, bind, interleave and
           local. A list of NUMA nodes that should be associated with the
           policy must be specified in NUMAMask=. For more details on each
           policy please see, set_mempolicy(2). For overall overview of NUMA
           support in Linux see, numa(7).

       NUMAMask=
           Controls the NUMA node list which will be applied alongside with
           selected NUMA policy. Takes a list of NUMA nodes and has the same
           syntax as a list of CPUs for CPUAffinity= option. Note that the
           list of NUMA nodes is not required for default and local policies
           and for preferred policy we expect a single NUMA node.

       IOSchedulingClass=
           Sets the I/O scheduling class for executed processes. Takes an
           integer between 0 and 3 or one of the strings none, realtime,
           best-effort or idle. If the empty string is assigned to this
           option, all prior assignments to both IOSchedulingClass= and
           IOSchedulingPriority= have no effect. See ioprio_set(2) for
           details.

       IOSchedulingPriority=
           Sets the I/O scheduling priority for executed processes. Takes an
           integer between 0 (highest priority) and 7 (lowest priority). The
           available priorities depend on the selected I/O scheduling class
           (see above). If the empty string is assigned to this option, all
           prior assignments to both IOSchedulingClass= and
           IOSchedulingPriority= have no effect. See ioprio_set(2) for
           details.

SANDBOXING         top

       The following sandboxing options are an effective way to limit the
       exposure of the system towards the unit's processes. It is
       recommended to turn on as many of these options for each unit as is
       possible without negatively affecting the process' ability to
       operate. Note that many of these sandboxing features are gracefully
       turned off on systems where the underlying security mechanism is not
       available. For example, ProtectSystem= has no effect if the kernel is
       built without file system namespacing or if the service manager runs
       in a container manager that makes file system namespacing unavailable
       to its payload. Similar, RestrictRealtime= has no effect on systems
       that lack support for SECCOMP system call filtering, or in containers
       where support for this is turned off.

       Also note that some sandboxing functionality is generally not
       available in user services (i.e. services run by the per-user service
       manager). Specifically, the various settings requiring file system
       namespacing support (such as ProtectSystem=) are not available, as
       the underlying kernel functionality is only accessible to privileged
       processes. However, most namespacing settings, that will not work on
       their own in user services, will work when used in conjunction with
       PrivateUsers=true.

       ProtectSystem=
           Takes a boolean argument or the special values "full" or
           "strict". If true, mounts the /usr and the boot loader
           directories (/boot and /efi) read-only for processes invoked by
           this unit. If set to "full", the /etc directory is mounted
           read-only, too. If set to "strict" the entire file system
           hierarchy is mounted read-only, except for the API file system
           subtrees /dev, /proc and /sys (protect these directories using
           PrivateDevices=, ProtectKernelTunables=, ProtectControlGroups=).
           This setting ensures that any modification of the vendor-supplied
           operating system (and optionally its configuration, and local
           mounts) is prohibited for the service. It is recommended to
           enable this setting for all long-running services, unless they
           are involved with system updates or need to modify the operating
           system in other ways. If this option is used, ReadWritePaths= may
           be used to exclude specific directories from being made
           read-only. This setting is implied if DynamicUser= is set. This
           setting cannot ensure protection in all cases. In general it has
           the same limitations as ReadOnlyPaths=, see below. Defaults to
           off.

       ProtectHome=
           Takes a boolean argument or the special values "read-only" or
           "tmpfs". If true, the directories /home, /root, and /run/user are
           made inaccessible and empty for processes invoked by this unit.
           If set to "read-only", the three directories are made read-only
           instead. If set to "tmpfs", temporary file systems are mounted on
           the three directories in read-only mode. The value "tmpfs" is
           useful to hide home directories not relevant to the processes
           invoked by the unit, while still allowing necessary directories
           to be made visible when listed in BindPaths= or
           BindReadOnlyPaths=.

           Setting this to "yes" is mostly equivalent to set the three
           directories in InaccessiblePaths=. Similarly, "read-only" is
           mostly equivalent to ReadOnlyPaths=, and "tmpfs" is mostly
           equivalent to TemporaryFileSystem= with ":ro".

           It is recommended to enable this setting for all long-running
           services (in particular network-facing ones), to ensure they
           cannot get access to private user data, unless the services
           actually require access to the user's private data. This setting
           is implied if DynamicUser= is set. This setting cannot ensure
           protection in all cases. In general it has the same limitations
           as ReadOnlyPaths=, see below.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       RuntimeDirectory=, StateDirectory=, CacheDirectory=, LogsDirectory=,
       ConfigurationDirectory=
           These options take a whitespace-separated list of directory
           names. The specified directory names must be relative, and may
           not include "..". If set, one or more directories by the
           specified names will be created (including their parents) below
           the locations defined in the following table, when the unit is
           started. Also, the corresponding environment variable is defined
           with the full path of directories. If multiple directories are
           set, then in the environment variable the paths are concatenated
           with colon (":").

           Table 2. Automatic directory creation and environment variables
           ┌────────────────────────┬────────────────┬───────────────────────┬──────────────────────────┐
           │Directory               Below path for Below path for        Environment              │
           │                        │ system units   user units            variable set             │
           ├────────────────────────┼────────────────┼───────────────────────┼──────────────────────────┤
           │RuntimeDirectory=       │ /run/          │ $XDG_RUNTIME_DIR$RUNTIME_DIRECTORY       │
           ├────────────────────────┼────────────────┼───────────────────────┼──────────────────────────┤
           │StateDirectory=         │ /var/lib/      │ $XDG_CONFIG_HOME$STATE_DIRECTORY         │
           ├────────────────────────┼────────────────┼───────────────────────┼──────────────────────────┤
           │CacheDirectory=         │ /var/cache/    │ $XDG_CACHE_HOME$CACHE_DIRECTORY         │
           ├────────────────────────┼────────────────┼───────────────────────┼──────────────────────────┤
           │LogsDirectory=          │ /var/log/      │ $XDG_CONFIG_HOME/log/ │ $LOGS_DIRECTORY          │
           ├────────────────────────┼────────────────┼───────────────────────┼──────────────────────────┤
           │ConfigurationDirectory= │ /etc/          │ $XDG_CONFIG_HOME$CONFIGURATION_DIRECTORY │
           └────────────────────────┴────────────────┴───────────────────────┴──────────────────────────┘
           In case of RuntimeDirectory= the innermost subdirectories are
           removed when the unit is stopped. It is possible to preserve the
           specified directories in this case if RuntimeDirectoryPreserve=
           is configured to restart or yes (see below). The directories
           specified with StateDirectory=, CacheDirectory=, LogsDirectory=,
           ConfigurationDirectory= are not removed when the unit is stopped.

           Except in case of ConfigurationDirectory=, the innermost
           specified directories will be owned by the user and group
           specified in User= and Group=. If the specified directories
           already exist and their owning user or group do not match the
           configured ones, all files and directories below the specified
           directories as well as the directories themselves will have their
           file ownership recursively changed to match what is configured.
           As an optimization, if the specified directories are already
           owned by the right user and group, files and directories below of
           them are left as-is, even if they do not match what is requested.
           The innermost specified directories will have their access mode
           adjusted to the what is specified in RuntimeDirectoryMode=,
           StateDirectoryMode=, CacheDirectoryMode=, LogsDirectoryMode= and
           ConfigurationDirectoryMode=.

           These options imply BindPaths= for the specified paths. When
           combined with RootDirectory= or RootImage= these paths always
           reside on the host and are mounted from there into the unit's
           file system namespace.

           If DynamicUser= is used in conjunction with StateDirectory=, the
           logic for CacheDirectory= and LogsDirectory= is slightly altered:
           the directories are created below /var/lib/private,
           /var/cache/private and /var/log/private, respectively, which are
           host directories made inaccessible to unprivileged users, which
           ensures that access to these directories cannot be gained through
           dynamic user ID recycling. Symbolic links are created to hide
           this difference in behaviour. Both from perspective of the host
           and from inside the unit, the relevant directories hence always
           appear directly below /var/lib, /var/cache and /var/log.

           Use RuntimeDirectory= to manage one or more runtime directories
           for the unit and bind their lifetime to the daemon runtime. This
           is particularly useful for unprivileged daemons that cannot
           create runtime directories in /run due to lack of privileges, and
           to make sure the runtime directory is cleaned up automatically
           after use. For runtime directories that require more complex or
           different configuration or lifetime guarantees, please consider
           using tmpfiles.d(5).

           The directories defined by these options are always created under
           the standard paths used by systemd (/var, /run, /etc, ...). If
           the service needs directories in a different location, a
           different mechanism has to be used to create them.

           tmpfiles.d(5) provides functionality that overlaps with these
           options. Using these options is recommended, because the lifetime
           of the directories is tied directly to the lifetime of the unit,
           and it is not necessary to ensure that the tmpfiles.d
           configuration is executed before the unit is started.

           To remove any of the directories created by these settings, use
           the systemctl clean ...  command on the relevant units, see
           systemctl(1) for details.

           Example: if a system service unit has the following,

               RuntimeDirectory=foo/bar baz

           the service manager creates /run/foo (if it does not exist),
           /run/foo/bar, and /run/baz. The directories /run/foo/bar and
           /run/baz except /run/foo are owned by the user and group
           specified in User= and Group=, and removed when the service is
           stopped.

           Example: if a system service unit has the following,

               RuntimeDirectory=foo/bar
               StateDirectory=aaa/bbb ccc

           then the environment variable "RUNTIME_DIRECTORY" is set with
           "/run/foo/bar", and "STATE_DIRECTORY" is set with
           "/var/lib/aaa/bbb:/var/lib/ccc".

       RuntimeDirectoryMode=, StateDirectoryMode=, CacheDirectoryMode=,
       LogsDirectoryMode=, ConfigurationDirectoryMode=
           Specifies the access mode of the directories specified in
           RuntimeDirectory=, StateDirectory=, CacheDirectory=,
           LogsDirectory=, or ConfigurationDirectory=, respectively, as an
           octal number. Defaults to 0755. See "Permissions" in
           path_resolution(7) for a discussion of the meaning of permission
           bits.

       RuntimeDirectoryPreserve=
           Takes a boolean argument or restart. If set to no (the default),
           the directories specified in RuntimeDirectory= are always removed
           when the service stops. If set to restart the directories are
           preserved when the service is both automatically and manually
           restarted. Here, the automatic restart means the operation
           specified in Restart=, and manual restart means the one triggered
           by systemctl restart foo.service. If set to yes, then the
           directories are not removed when the service is stopped. Note
           that since the runtime directory /run is a mount point of
           "tmpfs", then for system services the directories specified in
           RuntimeDirectory= are removed when the system is rebooted.

       TimeoutCleanSec=
           Configures a timeout on the clean-up operation requested through
           systemctl clean ..., see systemctl(1) for details. Takes the
           usual time values and defaults to infinity, i.e. by default no
           timeout is applied. If a timeout is configured the clean
           operation will be aborted forcibly when the timeout is reached,
           potentially leaving resources on disk.

       ReadWritePaths=, ReadOnlyPaths=, InaccessiblePaths=
           Sets up a new file system namespace for executed processes. These
           options may be used to limit access a process might have to the
           file system hierarchy. Each setting takes a space-separated list
           of paths relative to the host's root directory (i.e. the system
           running the service manager). Note that if paths contain
           symlinks, they are resolved relative to the root directory set
           with RootDirectory=/RootImage=.

           Paths listed in ReadWritePaths= are accessible from within the
           namespace with the same access modes as from outside of it. Paths
           listed in ReadOnlyPaths= are accessible for reading only, writing
           will be refused even if the usual file access controls would
           permit this. Nest ReadWritePaths= inside of ReadOnlyPaths= in
           order to provide writable subdirectories within read-only
           directories. Use ReadWritePaths= in order to allow-list specific
           paths for write access if ProtectSystem=strict is used.

           Paths listed in InaccessiblePaths= will be made inaccessible for
           processes inside the namespace along with everything below them
           in the file system hierarchy. This may be more restrictive than
           desired, because it is not possible to nest ReadWritePaths=,
           ReadOnlyPaths=, BindPaths=, or BindReadOnlyPaths= inside it. For
           a more flexible option, see TemporaryFileSystem=.

           Non-directory paths may be specified as well. These options may
           be specified more than once, in which case all paths listed will
           have limited access from within the namespace. If the empty
           string is assigned to this option, the specific list is reset,
           and all prior assignments have no effect.

           Paths in ReadWritePaths=, ReadOnlyPaths= and InaccessiblePaths=
           may be prefixed with "-", in which case they will be ignored when
           they do not exist. If prefixed with "+" the paths are taken
           relative to the root directory of the unit, as configured with
           RootDirectory=/RootImage=, instead of relative to the root
           directory of the host (see above). When combining "-" and "+" on
           the same path make sure to specify "-" first, and "+" second.

           Note that these settings will disconnect propagation of mounts
           from the unit's processes to the host. This means that this
           setting may not be used for services which shall be able to
           install mount points in the main mount namespace. For
           ReadWritePaths= and ReadOnlyPaths= propagation in the other
           direction is not affected, i.e. mounts created on the host
           generally appear in the unit processes' namespace, and mounts
           removed on the host also disappear there too. In particular, note
           that mount propagation from host to unit will result in
           unmodified mounts to be created in the unit's namespace, i.e.
           writable mounts appearing on the host will be writable in the
           unit's namespace too, even when propagated below a path marked
           with ReadOnlyPaths=! Restricting access with these options hence
           does not extend to submounts of a directory that are created
           later on. This means the lock-down offered by that setting is not
           complete, and does not offer full protection.

           Note that the effect of these settings may be undone by
           privileged processes. In order to set up an effective sandboxed
           environment for a unit it is thus recommended to combine these
           settings with either CapabilityBoundingSet=~CAP_SYS_ADMIN or
           SystemCallFilter=~@mount.

           These options are only available for system services and are not
           supported for services running in per-user instances of the
           service manager.

       TemporaryFileSystem=
           Takes a space-separated list of mount points for temporary file
           systems (tmpfs). If set, a new file system namespace is set up
           for executed processes, and a temporary file system is mounted on
           each mount point. This option may be specified more than once, in
           which case temporary file systems are mounted on all listed mount
           points. If the empty string is assigned to this option, the list
           is reset, and all prior assignments have no effect. Each mount
           point may optionally be suffixed with a colon (":") and mount
           options such as "size=10%" or "ro". By default, each temporary
           file system is mounted with "nodev,strictatime,mode=0755". These
           can be disabled by explicitly specifying the corresponding mount
           options, e.g., "dev" or "nostrictatime".

           This is useful to hide files or directories not relevant to the
           processes invoked by the unit, while necessary files or
           directories can be still accessed by combining with BindPaths= or
           BindReadOnlyPaths=:

           Example: if a unit has the following,

               TemporaryFileSystem=/var:ro
               BindReadOnlyPaths=/var/lib/systemd

           then the invoked processes by the unit cannot see any files or
           directories under /var except for /var/lib/systemd or its
           contents.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       PrivateTmp=
           Takes a boolean argument. If true, sets up a new file system
           namespace for the executed processes and mounts private /tmp/ and
           /var/tmp/ directories inside it that are not shared by processes
           outside of the namespace. This is useful to secure access to
           temporary files of the process, but makes sharing between
           processes via /tmp or /var/tmp impossible. If this is enabled,
           all temporary files created by a service in these directories
           will be removed after the service is stopped. Defaults to false.
           It is possible to run two or more units within the same private
           /tmp and /var/tmp namespace by using the JoinsNamespaceOf=
           directive, see systemd.unit(5) for details. This setting is
           implied if DynamicUser= is set. For this setting the same
           restrictions regarding mount propagation and privileges apply as
           for ReadOnlyPaths= and related calls, see above. Enabling this
           setting has the side effect of adding Requires= and After=
           dependencies on all mount units necessary to access /tmp and
           /var/tmp. Moreover an implicitly After= ordering on
           systemd-tmpfiles-setup.service(8) is added.

           Note that the implementation of this setting might be impossible
           (for example if mount namespaces are not available), and the unit
           should be written in a way that does not solely rely on this
           setting for security.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       PrivateDevices=
           Takes a boolean argument. If true, sets up a new /dev mount for
           the executed processes and only adds API pseudo devices such as
           /dev/null, /dev/zero or /dev/random (as well as the pseudo TTY
           subsystem) to it, but no physical devices such as /dev/sda,
           system memory /dev/mem, system ports /dev/port and others. This
           is useful to securely turn off physical device access by the
           executed process. Defaults to false. Enabling this option will
           install a system call filter to block low-level I/O system calls
           that are grouped in the @raw-io set, will also remove CAP_MKNOD
           and CAP_SYS_RAWIO from the capability bounding set for the unit
           (see above), and set DevicePolicy=closed (see
           systemd.resource-control(5) for details). Note that using this
           setting will disconnect propagation of mounts from the service to
           the host (propagation in the opposite direction continues to
           work). This means that this setting may not be used for services
           which shall be able to install mount points in the main mount
           namespace. The new /dev will be mounted read-only and 'noexec'.
           The latter may break old programs which try to set up executable
           memory by using mmap(2) of /dev/zero instead of using MAP_ANON.
           For this setting the same restrictions regarding mount
           propagation and privileges apply as for ReadOnlyPaths= and
           related calls, see above. If turned on and if running in user
           mode, or in system mode, but without the CAP_SYS_ADMIN capability
           (e.g. setting User=), NoNewPrivileges=yes is implied.

           Note that the implementation of this setting might be impossible
           (for example if mount namespaces are not available), and the unit
           should be written in a way that does not solely rely on this
           setting for security.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       PrivateNetwork=
           Takes a boolean argument. If true, sets up a new network
           namespace for the executed processes and configures only the
           loopback network device "lo" inside it. No other network devices
           will be available to the executed process. This is useful to turn
           off network access by the executed process. Defaults to false. It
           is possible to run two or more units within the same private
           network namespace by using the JoinsNamespaceOf= directive, see
           systemd.unit(5) for details. Note that this option will
           disconnect all socket families from the host, including
           AF_NETLINK and AF_UNIX. Effectively, for AF_NETLINK this means
           that device configuration events received from
           systemd-udevd.service(8) are not delivered to the unit's
           processes. And for AF_UNIX this has the effect that AF_UNIX
           sockets in the abstract socket namespace of the host will become
           unavailable to the unit's processes (however, those located in
           the file system will continue to be accessible).

           Note that the implementation of this setting might be impossible
           (for example if network namespaces are not available), and the
           unit should be written in a way that does not solely rely on this
           setting for security.

           When this option is used on a socket unit any sockets bound on
           behalf of this unit will be bound within a private network
           namespace. This may be combined with JoinsNamespaceOf= to listen
           on sockets inside of network namespaces of other services.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       NetworkNamespacePath=
           Takes an absolute file system path refererring to a Linux network
           namespace pseudo-file (i.e. a file like /proc/$PID/ns/net or a
           bind mount or symlink to one). When set the invoked processes are
           added to the network namespace referenced by that path. The path
           has to point to a valid namespace file at the moment the
           processes are forked off. If this option is used PrivateNetwork=
           has no effect. If this option is used together with
           JoinsNamespaceOf= then it only has an effect if this unit is
           started before any of the listed units that have PrivateNetwork=
           or NetworkNamespacePath= configured, as otherwise the network
           namespace of those units is reused.

           When this option is used on a socket unit any sockets bound on
           behalf of this unit will be bound within the specified network
           namespace.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       PrivateUsers=
           Takes a boolean argument. If true, sets up a new user namespace
           for the executed processes and configures a minimal user and
           group mapping, that maps the "root" user and group as well as the
           unit's own user and group to themselves and everything else to
           the "nobody" user and group. This is useful to securely detach
           the user and group databases used by the unit from the rest of
           the system, and thus to create an effective sandbox environment.
           All files, directories, processes, IPC objects and other
           resources owned by users/groups not equaling "root" or the unit's
           own will stay visible from within the unit but appear owned by
           the "nobody" user and group. If this mode is enabled, all unit
           processes are run without privileges in the host user namespace
           (regardless if the unit's own user/group is "root" or not).
           Specifically this means that the process will have zero process
           capabilities on the host's user namespace, but full capabilities
           within the service's user namespace. Settings such as
           CapabilityBoundingSet= will affect only the latter, and there's
           no way to acquire additional capabilities in the host's user
           namespace. Defaults to off.

           When this setting is set up by a per-user instance of the service
           manager, the mapping of the "root" user and group to itself is
           omitted (unless the user manager is root). Additionally, in the
           per-user instance manager case, the user namespace will be set up
           before most other namespaces. This means that combining
           PrivateUsers=true with other namespaces will enable use of
           features not normally supported by the per-user instances of the
           service manager.

           This setting is particularly useful in conjunction with
           RootDirectory=/RootImage=, as the need to synchronize the user
           and group databases in the root directory and on the host is
           reduced, as the only users and groups who need to be matched are
           "root", "nobody" and the unit's own user and group.

           Note that the implementation of this setting might be impossible
           (for example if user namespaces are not available), and the unit
           should be written in a way that does not solely rely on this
           setting for security.

       ProtectHostname=
           Takes a boolean argument. When set, sets up a new UTS namespace
           for the executed processes. In addition, changing hostname or
           domainname is prevented. Defaults to off.

           Note that the implementation of this setting might be impossible
           (for example if UTS namespaces are not available), and the unit
           should be written in a way that does not solely rely on this
           setting for security.

           Note that when this option is enabled for a service hostname
           changes no longer propagate from the system into the service, it
           is hence not suitable for services that need to take notice of
           system hostname changes dynamically.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       ProtectClock=
           Takes a boolean argument. If set, writes to the hardware clock or
           system clock will be denied. It is recommended to turn this on
           for most services that do not need modify the clock. Defaults to
           off. Enabling this option removes CAP_SYS_TIME and CAP_WAKE_ALARM
           from the capability bounding set for this unit, installs a system
           call filter to block calls that can set the clock, and
           DeviceAllow=char-rtc r is implied. This ensures /dev/rtc0,
           /dev/rtc1, etc. are made read-only to the service. See
           systemd.resource-control(5) for the details about DeviceAllow=.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       ProtectKernelTunables=
           Takes a boolean argument. If true, kernel variables accessible
           through /proc/sys, /sys, /proc/sysrq-trigger,
           /proc/latency_stats, /proc/acpi, /proc/timer_stats, /proc/fs and
           /proc/irq will be made read-only to all processes of the unit.
           Usually, tunable kernel variables should be initialized only at
           boot-time, for example with the sysctl.d(5) mechanism. Few
           services need to write to these at runtime; it is hence
           recommended to turn this on for most services. For this setting
           the same restrictions regarding mount propagation and privileges
           apply as for ReadOnlyPaths= and related calls, see above.
           Defaults to off. If turned on and if running in user mode, or in
           system mode, but without the CAP_SYS_ADMIN capability (e.g.
           services for which User= is set), NoNewPrivileges=yes is implied.
           Note that this option does not prevent indirect changes to kernel
           tunables effected by IPC calls to other processes. However,
           InaccessiblePaths= may be used to make relevant IPC file system
           objects inaccessible. If ProtectKernelTunables= is set,
           MountAPIVFS=yes is implied.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       ProtectKernelModules=
           Takes a boolean argument. If true, explicit module loading will
           be denied. This allows module load and unload operations to be
           turned off on modular kernels. It is recommended to turn this on
           for most services that do not need special file systems or extra
           kernel modules to work. Defaults to off. Enabling this option
           removes CAP_SYS_MODULE from the capability bounding set for the
           unit, and installs a system call filter to block module system
           calls, also /usr/lib/modules is made inaccessible. For this
           setting the same restrictions regarding mount propagation and
           privileges apply as for ReadOnlyPaths= and related calls, see
           above. Note that limited automatic module loading due to user
           configuration or kernel mapping tables might still happen as side
           effect of requested user operations, both privileged and
           unprivileged. To disable module auto-load feature please see
           sysctl.d(5) kernel.modules_disabled mechanism and
           /proc/sys/kernel/modules_disabled documentation. If turned on and
           if running in user mode, or in system mode, but without the
           CAP_SYS_ADMIN capability (e.g. setting User=),
           NoNewPrivileges=yes is implied.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       ProtectKernelLogs=
           Takes a boolean argument. If true, access to the kernel log ring
           buffer will be denied. It is recommended to turn this on for most
           services that do not need to read from or write to the kernel log
           ring buffer. Enabling this option removes CAP_SYSLOG from the
           capability bounding set for this unit, and installs a system call
           filter to block the syslog(2) system call (not to be confused
           with the libc API syslog(3) for userspace logging). The kernel
           exposes its log buffer to userspace via /dev/kmsg and /proc/kmsg.
           If enabled, these are made inaccessible to all the processes in
           the unit.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       ProtectControlGroups=
           Takes a boolean argument. If true, the Linux Control Groups (‐
           cgroups(7)) hierarchies accessible through /sys/fs/cgroup will be
           made read-only to all processes of the unit. Except for container
           managers no services should require write access to the control
           groups hierarchies; it is hence recommended to turn this on for
           most services. For this setting the same restrictions regarding
           mount propagation and privileges apply as for ReadOnlyPaths= and
           related calls, see above. Defaults to off. If
           ProtectControlGroups= is set, MountAPIVFS=yes is implied.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       RestrictAddressFamilies=
           Restricts the set of socket address families accessible to the
           processes of this unit. Takes a space-separated list of address
           family names to allow-list, such as AF_UNIX, AF_INET or AF_INET6.
           When prefixed with ~ the listed address families will be applied
           as deny list, otherwise as allow list. Note that this restricts
           access to the socket(2) system call only. Sockets passed into the
           process by other means (for example, by using socket activation
           with socket units, see systemd.socket(5)) are unaffected. Also,
           sockets created with socketpair() (which creates connected
           AF_UNIX sockets only) are unaffected. Note that this option has
           no effect on 32-bit x86, s390, s390x, mips, mips-le, ppc, ppc-le,
           ppc64, ppc64-le and is ignored (but works correctly on other
           ABIs, including x86-64). Note that on systems supporting multiple
           ABIs (such as x86/x86-64) it is recommended to turn off
           alternative ABIs for services, so that they cannot be used to
           circumvent the restrictions of this option. Specifically, it is
           recommended to combine this option with
           SystemCallArchitectures=native or similar. If running in user
           mode, or in system mode, but without the CAP_SYS_ADMIN capability
           (e.g. setting User=nobody), NoNewPrivileges=yes is implied. By
           default, no restrictions apply, all address families are
           accessible to processes. If assigned the empty string, any
           previous address family restriction changes are undone. This
           setting does not affect commands prefixed with "+".

           Use this option to limit exposure of processes to remote access,
           in particular via exotic and sensitive network protocols, such as
           AF_PACKET. Note that in most cases, the local AF_UNIX address
           family should be included in the configured allow list as it is
           frequently used for local communication, including for syslog(2)
           logging.

       RestrictNamespaces=
           Restricts access to Linux namespace functionality for the
           processes of this unit. For details about Linux namespaces, see
           namespaces(7). Either takes a boolean argument, or a
           space-separated list of namespace type identifiers. If false (the
           default), no restrictions on namespace creation and switching are
           made. If true, access to any kind of namespacing is prohibited.
           Otherwise, a space-separated list of namespace type identifiers
           must be specified, consisting of any combination of: cgroup, ipc,
           net, mnt, pid, user and uts. Any namespace type listed is made
           accessible to the unit's processes, access to namespace types not
           listed is prohibited (allow-listing). By prepending the list with
           a single tilde character ("~") the effect may be inverted: only
           the listed namespace types will be made inaccessible, all
           unlisted ones are permitted (deny-listing). If the empty string
           is assigned, the default namespace restrictions are applied,
           which is equivalent to false. This option may appear more than
           once, in which case the namespace types are merged by OR, or by
           AND if the lines are prefixed with "~" (see examples below).
           Internally, this setting limits access to the unshare(2),
           clone(2) and setns(2) system calls, taking the specified flags
           parameters into account. Note that — if this option is used — in
           addition to restricting creation and switching of the specified
           types of namespaces (or all of them, if true) access to the
           setns() system call with a zero flags parameter is prohibited.
           This setting is only supported on x86, x86-64, mips, mips-le,
           mips64, mips64-le, mips64-n32, mips64-le-n32, ppc64, ppc64-le,
           s390 and s390x, and enforces no restrictions on other
           architectures. If running in user mode, or in system mode, but
           without the CAP_SYS_ADMIN capability (e.g. setting User=),
           NoNewPrivileges=yes is implied.

           Example: if a unit has the following,

               RestrictNamespaces=cgroup ipc
               RestrictNamespaces=cgroup net

           then cgroup, ipc, and net are set. If the second line is prefixed
           with "~", e.g.,

               RestrictNamespaces=cgroup ipc
               RestrictNamespaces=~cgroup net

           then, only ipc is set.

       LockPersonality=
           Takes a boolean argument. If set, locks down the personality(2)
           system call so that the kernel execution domain may not be
           changed from the default or the personality selected with
           Personality= directive. This may be useful to improve security,
           because odd personality emulations may be poorly tested and
           source of vulnerabilities. If running in user mode, or in system
           mode, but without the CAP_SYS_ADMIN capability (e.g. setting
           User=), NoNewPrivileges=yes is implied.

       MemoryDenyWriteExecute=
           Takes a boolean argument. If set, attempts to create memory
           mappings that are writable and executable at the same time, or to
           change existing memory mappings to become executable, or mapping
           shared memory segments as executable are prohibited.
           Specifically, a system call filter is added that rejects mmap(2)
           system calls with both PROT_EXEC and PROT_WRITE set, mprotect(2)
           or pkey_mprotect(2) system calls with PROT_EXEC set and shmat(2)
           system calls with SHM_EXEC set. Note that this option is
           incompatible with programs and libraries that generate program
           code dynamically at runtime, including JIT execution engines,
           executable stacks, and code "trampoline" feature of various C
           compilers. This option improves service security, as it makes
           harder for software exploits to change running code dynamically.
           However, the protection can be circumvented, if the service can
           write to a filesystem, which is not mounted with noexec (such as
           /dev/shm), or it can use memfd_create(). This can be prevented by
           making such file systems inaccessible to the service (e.g.
           InaccessiblePaths=/dev/shm) and installing further system call
           filters (SystemCallFilter=~memfd_create). Note that this feature
           is fully available on x86-64, and partially on x86. Specifically,
           the shmat() protection is not available on x86. Note that on
           systems supporting multiple ABIs (such as x86/x86-64) it is
           recommended to turn off alternative ABIs for services, so that
           they cannot be used to circumvent the restrictions of this
           option. Specifically, it is recommended to combine this option
           with SystemCallArchitectures=native or similar. If running in
           user mode, or in system mode, but without the CAP_SYS_ADMIN
           capability (e.g. setting User=), NoNewPrivileges=yes is implied.

       RestrictRealtime=
           Takes a boolean argument. If set, any attempts to enable realtime
           scheduling in a process of the unit are refused. This restricts
           access to realtime task scheduling policies such as SCHED_FIFO,
           SCHED_RR or SCHED_DEADLINE. See sched(7) for details about these
           scheduling policies. If running in user mode, or in system mode,
           but without the CAP_SYS_ADMIN capability (e.g. setting User=),
           NoNewPrivileges=yes is implied. Realtime scheduling policies may
           be used to monopolize CPU time for longer periods of time, and
           may hence be used to lock up or otherwise trigger
           Denial-of-Service situations on the system. It is hence
           recommended to restrict access to realtime scheduling to the few
           programs that actually require them. Defaults to off.

       RestrictSUIDSGID=
           Takes a boolean argument. If set, any attempts to set the
           set-user-ID (SUID) or set-group-ID (SGID) bits on files or
           directories will be denied (for details on these bits see
           inode(7)). If running in user mode, or in system mode, but
           without the CAP_SYS_ADMIN capability (e.g. setting User=),
           NoNewPrivileges=yes is implied. As the SUID/SGID bits are
           mechanisms to elevate privileges, and allows users to acquire the
           identity of other users, it is recommended to restrict creation
           of SUID/SGID files to the few programs that actually require
           them. Note that this restricts marking of any type of file system
           object with these bits, including both regular files and
           directories (where the SGID is a different meaning than for
           files, see documentation). This option is implied if DynamicUser=
           is enabled. Defaults to off.

       RemoveIPC=
           Takes a boolean parameter. If set, all System V and POSIX IPC
           objects owned by the user and group the processes of this unit
           are run as are removed when the unit is stopped. This setting
           only has an effect if at least one of User=, Group= and
           DynamicUser= are used. It has no effect on IPC objects owned by
           the root user. Specifically, this removes System V semaphores, as
           well as System V and POSIX shared memory segments and message
           queues. If multiple units use the same user or group the IPC
           objects are removed when the last of these units is stopped. This
           setting is implied if DynamicUser= is set.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       PrivateMounts=
           Takes a boolean parameter. If set, the processes of this unit
           will be run in their own private file system (mount) namespace
           with all mount propagation from the processes towards the host's
           main file system namespace turned off. This means any file system
           mount points established or removed by the unit's processes will
           be private to them and not be visible to the host. However, file
           system mount points established or removed on the host will be
           propagated to the unit's processes. See mount_namespaces(7) for
           details on file system namespaces. Defaults to off.

           When turned on, this executes three operations for each invoked
           process: a new CLONE_NEWNS namespace is created, after which all
           existing mounts are remounted to MS_SLAVE to disable propagation
           from the unit's processes to the host (but leaving propagation in
           the opposite direction in effect). Finally, the mounts are
           remounted again to the propagation mode configured with
           MountFlags=, see below.

           File system namespaces are set up individually for each process
           forked off by the service manager. Mounts established in the
           namespace of the process created by ExecStartPre= will hence be
           cleaned up automatically as soon as that process exits and will
           not be available to subsequent processes forked off for
           ExecStart= (and similar applies to the various other commands
           configured for units). Similarly, JoinsNamespaceOf= does not
           permit sharing kernel mount namespaces between units, it only
           enables sharing of the /tmp/ and /var/tmp/ directories.

           Other file system namespace unit settings — PrivateMounts=,
           PrivateTmp=, PrivateDevices=, ProtectSystem=, ProtectHome=,
           ReadOnlyPaths=, InaccessiblePaths=, ReadWritePaths=, ... — also
           enable file system namespacing in a fashion equivalent to this
           option. Hence it is primarily useful to explicitly request this
           behaviour if none of the other settings are used.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       MountFlags=
           Takes a mount propagation setting: shared, slave or private,
           which controls whether file system mount points in the file
           system namespaces set up for this unit's processes will receive
           or propagate mounts and unmounts from other file system
           namespaces. See mount(2) for details on mount propagation, and
           the three propagation flags in particular.

           This setting only controls the final propagation setting in
           effect on all mount points of the file system namespace created
           for each process of this unit. Other file system namespacing unit
           settings (see the discussion in PrivateMounts= above) will
           implicitly disable mount and unmount propagation from the unit's
           processes towards the host by changing the propagation setting of
           all mount points in the unit's file system namespace to slave
           first. Setting this option to shared does not reestablish
           propagation in that case.

           If not set – but file system namespaces are enabled through
           another file system namespace unit setting – shared mount
           propagation is used, but — as mentioned — as slave is applied
           first, propagation from the unit's processes to the host is still
           turned off.

           It is not recommended to use private mount propagation for units,
           as this means temporary mounts (such as removable media) of the
           host will stay mounted and thus indefinitely busy in forked off
           processes, as unmount propagation events won't be received by the
           file system namespace of the unit.

           Usually, it is best to leave this setting unmodified, and use
           higher level file system namespacing options instead, in
           particular PrivateMounts=, see above.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

SYSTEM CALL FILTERING         top

       SystemCallFilter=
           Takes a space-separated list of system call names. If this
           setting is used, all system calls executed by the unit processes
           except for the listed ones will result in immediate process
           termination with the SIGSYS signal (allow-listing). (See
           SystemCallErrorNumber= below for changing the default action). If
           the first character of the list is "~", the effect is inverted:
           only the listed system calls will result in immediate process
           termination (deny-listing). Deny-listed system calls and system
           call groups may optionally be suffixed with a colon (":") and
           "errno" error number (between 0 and 4095) or errno name such as
           EPERM, EACCES or EUCLEAN (see errno(3) for a full list). This
           value will be returned when a deny-listed system call is
           triggered, instead of terminating the processes immediately. This
           value takes precedence over the one given in
           SystemCallErrorNumber=, see below. If running in user mode, or in
           system mode, but without the CAP_SYS_ADMIN capability (e.g.
           setting User=nobody), NoNewPrivileges=yes is implied. This
           feature makes use of the Secure Computing Mode 2 interfaces of
           the kernel ('seccomp filtering') and is useful for enforcing a
           minimal sandboxing environment. Note that the execve, exit,
           exit_group, getrlimit, rt_sigreturn, sigreturn system calls and
           the system calls for querying time and sleeping are implicitly
           allow-listed and do not need to be listed explicitly. This option
           may be specified more than once, in which case the filter masks
           are merged. If the empty string is assigned, the filter is reset,
           all prior assignments will have no effect. This does not affect
           commands prefixed with "+".

           Note that on systems supporting multiple ABIs (such as
           x86/x86-64) it is recommended to turn off alternative ABIs for
           services, so that they cannot be used to circumvent the
           restrictions of this option. Specifically, it is recommended to
           combine this option with SystemCallArchitectures=native or
           similar.

           Note that strict system call filters may impact execution and
           error handling code paths of the service invocation.
           Specifically, access to the execve system call is required for
           the execution of the service binary — if it is blocked service
           invocation will necessarily fail. Also, if execution of the
           service binary fails for some reason (for example: missing
           service executable), the error handling logic might require
           access to an additional set of system calls in order to process
           and log this failure correctly. It might be necessary to
           temporarily disable system call filters in order to simplify
           debugging of such failures.

           If you specify both types of this option (i.e. allow-listing and
           deny-listing), the first encountered will take precedence and
           will dictate the default action (termination or approval of a
           system call). Then the next occurrences of this option will add
           or delete the listed system calls from the set of the filtered
           system calls, depending of its type and the default action. (For
           example, if you have started with an allow list rule for read and
           write, and right after it add a deny list rule for write, then
           write will be removed from the set.)

           As the number of possible system calls is large, predefined sets
           of system calls are provided. A set starts with "@" character,
           followed by name of the set.

           Table 3. Currently predefined system call sets
           ┌────────────────┬───────────────────────────┐
           │Set             Description               │
           ├────────────────┼───────────────────────────┤
           │@aio            │ Asynchronous I/O (‐       │
           │                │ io_setup(2),              │
           │                │ io_submit(2), and related │
           │                │ calls)                    │
           ├────────────────┼───────────────────────────┤
           │@basic-io       │ System calls for basic    │
           │                │ I/O: reading, writing,    │
           │                │ seeking, file descriptor  │
           │                │ duplication and closing   │
           │                │ (read(2), write(2), and   │
           │                │ related calls)            │
           ├────────────────┼───────────────────────────┤
           │@chown          │ Changing file ownership   │
           │                │ (chown(2), fchownat(2),   │
           │                │ and related calls)        │
           ├────────────────┼───────────────────────────┤
           │@clock          │ System calls for changing │
           │                │ the system clock (‐       │
           │                │ adjtimex(2),              │
           │                │ settimeofday(2), and      │
           │                │ related calls)            │
           ├────────────────┼───────────────────────────┤
           │@cpu-emulation  │ System calls for CPU      │
           │                │ emulation functionality   │
           │                │ (vm86(2) and related      │
           │                │ calls)                    │
           ├────────────────┼───────────────────────────┤
           │@debug          │ Debugging, performance    │
           │                │ monitoring and tracing    │
           │                │ functionality (ptrace(2), │
           │                │ perf_event_open(2) and    │
           │                │ related calls)            │
           ├────────────────┼───────────────────────────┤
           │@file-system    │ File system operations:   │
           │                │ opening, creating files   │
           │                │ and directories for read  │
           │                │ and write, renaming and   │
           │                │ removing them, reading    │
           │                │ file properties, or       │
           │                │ creating hard and         │
           │                │ symbolic links            │
           ├────────────────┼───────────────────────────┤
           │@io-event       │ Event loop system calls   │
           │                │ (poll(2), select(2),      │
           │                │ epoll(7), eventfd(2) and  │
           │                │ related calls)            │
           ├────────────────┼───────────────────────────┤
           │@ipc            │ Pipes, SysV IPC, POSIX    │
           │                │ Message Queues and other  │
           │                │ IPC (mq_overview(7),      │
           │                │ svipc(7))                 │
           ├────────────────┼───────────────────────────┤
           │@keyring        │ Kernel keyring access (‐  │
           │                │ keyctl(2) and related     │
           │                │ calls)                    │
           ├────────────────┼───────────────────────────┤
           │@memlock        │ Locking of memory in RAM  │
           │                │ (mlock(2), mlockall(2)    │
           │                │ and related calls)        │
           ├────────────────┼───────────────────────────┤
           │@module         │ Loading and unloading of  │
           │                │ kernel modules (‐         │
           │                │ init_module(2),           │
           │                │ delete_module(2) and      │
           │                │ related calls)            │
           ├────────────────┼───────────────────────────┤
           │@mount          │ Mounting and unmounting   │
           │                │ of file systems (‐        │
           │                │ mount(2), chroot(2), and  │
           │                │ related calls)            │
           ├────────────────┼───────────────────────────┤
           │@network-io     │ Socket I/O (including     │
           │                │ local AF_UNIX):           │
           │                │ socket(7), unix(7)        │
           ├────────────────┼───────────────────────────┤
           │@obsolete       │ Unusual, obsolete or      │
           │                │ unimplemented (‐          │
           │                │ create_module(2),         │
           │                │ gtty(2), ...)             │
           ├────────────────┼───────────────────────────┤
           │@privileged     │ All system calls which    │
           │                │ need super-user           │
           │                │ capabilities (‐           │
           │                │ capabilities(7))          │
           ├────────────────┼───────────────────────────┤
           │@process        │ Process control,          │
           │                │ execution, namespaceing   │
           │                │ operations (clone(2),     │
           │                │ kill(2), namespaces(7),   │
           │                │ ...)                      │
           ├────────────────┼───────────────────────────┤
           │@raw-io         │ Raw I/O port access (‐    │
           │                │ ioperm(2), iopl(2),       │
           │                │ pciconfig_read(), ...)    │
           ├────────────────┼───────────────────────────┤
           │@reboot         │ System calls for          │
           │                │ rebooting and reboot      │
           │                │ preparation (reboot(2),   │
           │                │ kexec(), ...)             │
           ├────────────────┼───────────────────────────┤
           │@resources      │ System calls for changing │
           │                │ resource limits, memory   │
           │                │ and scheduling parameters │
           │                │ (setrlimit(2),            │
           │                │ setpriority(2), ...)      │
           ├────────────────┼───────────────────────────┤
           │@setuid         │ System calls for changing │
           │                │ user ID and group ID      │
           │                │ credentials, (setuid(2),  │
           │                │ setgid(2), setresuid(2),  │
           │                │ ...)                      │
           ├────────────────┼───────────────────────────┤
           │@signal         │ System calls for          │
           │                │ manipulating and handling │
           │                │ process signals (‐        │
           │                │ signal(2),                │
           │                │ sigprocmask(2), ...)      │
           ├────────────────┼───────────────────────────┤
           │@swap           │ System calls for          │
           │                │ enabling/disabling swap   │
           │                │ devices (swapon(2),       │
           │                │ swapoff(2))               │
           ├────────────────┼───────────────────────────┤
           │@sync           │ Synchronizing files and   │
           │                │ memory to disk (fsync(2), │
           │                │ msync(2), and related     │
           │                │ calls)                    │
           ├────────────────┼───────────────────────────┤
           │@system-service │ A reasonable set of       │
           │                │ system calls used by      │
           │                │ common system services,   │
           │                │ excluding any special     │
           │                │ purpose calls. This is    │
           │                │ the recommended starting  │
           │                │ point for allow-listing   │
           │                │ system calls for system   │
           │                │ services, as it contains  │
           │                │ what is typically needed  │
           │                │ by system services, but   │
           │                │ excludes overly specific  │
           │                │ interfaces. For example,  │
           │                │ the following APIs are    │
           │                │ excluded: "@clock",       │
           │                │ "@mount", "@swap",        │
           │                │ "@reboot".                │
           ├────────────────┼───────────────────────────┤
           │@timer          │ System calls for          │
           │                │ scheduling operations by  │
           │                │ time (alarm(2),           │
           │                │ timer_create(2), ...)     │
           └────────────────┴───────────────────────────┘
           Note, that as new system calls are added to the kernel,
           additional system calls might be added to the groups above.
           Contents of the sets may also change between systemd versions. In
           addition, the list of system calls depends on the kernel version
           and architecture for which systemd was compiled. Use
           systemd-analyze syscall-filter to list the actual list of system
           calls in each filter.

           Generally, allow-listing system calls (rather than deny-listing)
           is the safer mode of operation. It is recommended to enforce
           system call allow lists for all long-running system services.
           Specifically, the following lines are a relatively safe basic
           choice for the majority of system services:

               [Service]
               SystemCallFilter=@system-service
               SystemCallErrorNumber=EPERM

           Note that various kernel system calls are defined redundantly:
           there are multiple system calls for executing the same operation.
           For example, the pidfd_send_signal() system call may be used to
           execute operations similar to what can be done with the older
           kill() system call, hence blocking the latter without the former
           only provides weak protection. Since new system calls are added
           regularly to the kernel as development progresses, keeping system
           call deny lists comprehensive requires constant work. It is thus
           recommended to use allow-listing instead, which offers the
           benefit that new system calls are by default implicitly blocked
           until the allow list is updated.

           Also note that a number of system calls are required to be
           accessible for the dynamic linker to work. The dynamic linker is
           required for running most regular programs (specifically: all
           dynamic ELF binaries, which is how most distributions build
           packaged programs). This means that blocking these system calls
           (which include open(), openat() or mmap()) will make most
           programs typically shipped with generic distributions unusable.

           It is recommended to combine the file system namespacing related
           options with SystemCallFilter=~@mount, in order to prohibit the
           unit's processes to undo the mappings. Specifically these are the
           options PrivateTmp=, PrivateDevices=, ProtectSystem=,
           ProtectHome=, ProtectKernelTunables=, ProtectControlGroups=,
           ProtectKernelLogs=, ProtectClock=, ReadOnlyPaths=,
           InaccessiblePaths= and ReadWritePaths=.

       SystemCallErrorNumber=
           Takes an "errno" error number (between 1 and 4095) or errno name
           such as EPERM, EACCES or EUCLEAN, to return when the system call
           filter configured with SystemCallFilter= is triggered, instead of
           terminating the process immediately. See errno(3) for a full list
           of error codes. When this setting is not used, or when the empty
           string is assigned, the process will be terminated immediately
           when the filter is triggered.

       SystemCallArchitectures=
           Takes a space-separated list of architecture identifiers to
           include in the system call filter. The known architecture
           identifiers are the same as for ConditionArchitecture= described
           in systemd.unit(5), as well as x32, mips64-n32, mips64-le-n32,
           and the special identifier native. The special identifier native
           implicitly maps to the native architecture of the system (or more
           precisely: to the architecture the system manager is compiled
           for). If running in user mode, or in system mode, but without the
           CAP_SYS_ADMIN capability (e.g. setting User=nobody),
           NoNewPrivileges=yes is implied. By default, this option is set to
           the empty list, i.e. no filtering is applied.

           If this setting is used, processes of this unit will only be
           permitted to call native system calls, and system calls of the
           specified architectures. For the purposes of this option, the x32
           architecture is treated as including x86-64 system calls.
           However, this setting still fulfills its purpose, as explained
           below, on x32.

           System call filtering is not equally effective on all
           architectures. For example, on x86 filtering of network
           socket-related calls is not possible, due to ABI limitations — a
           limitation that x86-64 does not have, however. On systems
           supporting multiple ABIs at the same time — such as x86/x86-64 —
           it is hence recommended to limit the set of permitted system call
           architectures so that secondary ABIs may not be used to
           circumvent the restrictions applied to the native ABI of the
           system. In particular, setting SystemCallArchitectures=native is
           a good choice for disabling non-native ABIs.

           System call architectures may also be restricted system-wide via
           the SystemCallArchitectures= option in the global configuration.
           See systemd-system.conf(5) for details.

ENVIRONMENT         top

       Environment=
           Sets environment variables for executed processes. Takes a
           space-separated list of variable assignments. This option may be
           specified more than once, in which case all listed variables will
           be set. If the same variable is set twice, the later setting will
           override the earlier setting. If the empty string is assigned to
           this option, the list of environment variables is reset, all
           prior assignments have no effect. Variable expansion is not
           performed inside the strings, however, specifier expansion is
           possible. The $ character has no special meaning. If you need to
           assign a value containing spaces or the equals sign to a
           variable, use double quotes (") for the assignment.

           Example:

               Environment="VAR1=word1 word2" VAR2=word3 "VAR3=$word 5 6"

           gives three variables "VAR1", "VAR2", "VAR3" with the values
           "word1 word2", "word3", "$word 5 6".

           See environ(7) for details about environment variables.

           Note that environment variables are not suitable for passing
           secrets (such as passwords, key material, ...) to service
           processes. Environment variables set for a unit are exposed to
           unprivileged clients via D-Bus IPC, and generally not understood
           as being data that requires protection. Moreover, environment
           variables are propagated down the process tree, including across
           security boundaries (such as setuid/setgid executables), and
           hence might leak to processes that should not have access to the
           secret data.

       EnvironmentFile=
           Similar to Environment= but reads the environment variables from
           a text file. The text file should contain new-line-separated
           variable assignments. Empty lines, lines without an "="
           separator, or lines starting with ; or # will be ignored, which
           may be used for commenting. A line ending with a backslash will
           be concatenated with the following one, allowing multiline
           variable definitions. The parser strips leading and trailing
           whitespace from the values of assignments, unless you use double
           quotes (").

           C escapes[5] are supported, but not most control characters[6].
           "\t" and "\n" can be used to insert tabs and newlines within
           EnvironmentFile=.

           The argument passed should be an absolute filename or wildcard
           expression, optionally prefixed with "-", which indicates that if
           the file does not exist, it will not be read and no error or
           warning message is logged. This option may be specified more than
           once in which case all specified files are read. If the empty
           string is assigned to this option, the list of file to read is
           reset, all prior assignments have no effect.

           The files listed with this directive will be read shortly before
           the process is executed (more specifically, after all processes
           from a previous unit state terminated. This means you can
           generate these files in one unit state, and read it with this
           option in the next. The files are read from the file system of
           the service manager, before any file system changes like bind
           mounts take place).

           Settings from these files override settings made with
           Environment=. If the same variable is set twice from these files,
           the files will be read in the order they are specified and the
           later setting will override the earlier setting.

       PassEnvironment=
           Pass environment variables set for the system service manager to
           executed processes. Takes a space-separated list of variable
           names. This option may be specified more than once, in which case
           all listed variables will be passed. If the empty string is
           assigned to this option, the list of environment variables to
           pass is reset, all prior assignments have no effect. Variables
           specified that are not set for the system manager will not be
           passed and will be silently ignored. Note that this option is
           only relevant for the system service manager, as system services
           by default do not automatically inherit any environment variables
           set for the service manager itself. However, in case of the user
           service manager all environment variables are passed to the
           executed processes anyway, hence this option is without effect
           for the user service manager.

           Variables set for invoked processes due to this setting are
           subject to being overridden by those configured with Environment=
           or EnvironmentFile=.

           C escapes[5] are supported, but not most control characters[6].
           "\t" and "\n" can be used to insert tabs and newlines within
           EnvironmentFile=.

           Example:

               PassEnvironment=VAR1 VAR2 VAR3

           passes three variables "VAR1", "VAR2", "VAR3" with the values set
           for those variables in PID1.

           See environ(7) for details about environment variables.

       UnsetEnvironment=
           Explicitly unset environment variable assignments that would
           normally be passed from the service manager to invoked processes
           of this unit. Takes a space-separated list of variable names or
           variable assignments. This option may be specified more than
           once, in which case all listed variables/assignments will be
           unset. If the empty string is assigned to this option, the list
           of environment variables/assignments to unset is reset. If a
           variable assignment is specified (that is: a variable name,
           followed by "=", followed by its value), then any environment
           variable matching this precise assignment is removed. If a
           variable name is specified (that is a variable name without any
           following "=" or value), then any assignment matching the
           variable name, regardless of its value is removed. Note that the
           effect of UnsetEnvironment= is applied as final step when the
           environment list passed to executed processes is compiled. That
           means it may undo assignments from any configuration source,
           including assignments made through Environment= or
           EnvironmentFile=, inherited from the system manager's global set
           of environment variables, inherited via PassEnvironment=, set by
           the service manager itself (such as $NOTIFY_SOCKET and such), or
           set by a PAM module (in case PAMName= is used).

           See environ(7) for details about environment variables.

LOGGING AND STANDARD INPUT/OUTPUT         top

       StandardInput=
           Controls where file descriptor 0 (STDIN) of the executed
           processes is connected to. Takes one of null, tty, tty-force,
           tty-fail, data, file:path, socket or fd:name.

           If null is selected, standard input will be connected to
           /dev/null, i.e. all read attempts by the process will result in
           immediate EOF.

           If tty is selected, standard input is connected to a TTY (as
           configured by TTYPath=, see below) and the executed process
           becomes the controlling process of the terminal. If the terminal
           is already being controlled by another process, the executed
           process waits until the current controlling process releases the
           terminal.

           tty-force is similar to tty, but the executed process is
           forcefully and immediately made the controlling process of the
           terminal, potentially removing previous controlling processes
           from the terminal.

           tty-fail is similar to tty, but if the terminal already has a
           controlling process start-up of the executed process fails.

           The data option may be used to configure arbitrary textual or
           binary data to pass via standard input to the executed process.
           The data to pass is configured via
           StandardInputText=/StandardInputData= (see below). Note that the
           actual file descriptor type passed (memory file, regular file,
           UNIX pipe, ...) might depend on the kernel and available
           privileges. In any case, the file descriptor is read-only, and
           when read returns the specified data followed by EOF.

           The file:path option may be used to connect a specific file
           system object to standard input. An absolute path following the
           ":" character is expected, which may refer to a regular file, a
           FIFO or special file. If an AF_UNIX socket in the file system is
           specified, a stream socket is connected to it. The latter is
           useful for connecting standard input of processes to arbitrary
           system services.

           The socket option is valid in socket-activated services only, and
           requires the relevant socket unit file (see systemd.socket(5) for
           details) to have Accept=yes set, or to specify a single socket
           only. If this option is set, standard input will be connected to
           the socket the service was activated from, which is primarily
           useful for compatibility with daemons designed for use with the
           traditional inetd(8) socket activation daemon.

           The fd:name option connects standard input to a specific, named
           file descriptor provided by a socket unit. The name may be
           specified as part of this option, following a ":" character (e.g.
           "fd:foobar"). If no name is specified, the name "stdin" is
           implied (i.e.  "fd" is equivalent to "fd:stdin"). At least one
           socket unit defining the specified name must be provided via the
           Sockets= option, and the file descriptor name may differ from the
           name of its containing socket unit. If multiple matches are
           found, the first one will be used. See FileDescriptorName= in
           systemd.socket(5) for more details about named file descriptors
           and their ordering.

           This setting defaults to null.

       StandardOutput=
           Controls where file descriptor 1 (stdout) of the executed
           processes is connected to. Takes one of inherit, null, tty,
           journal, kmsg, journal+console, kmsg+console, file:path,
           append:path, socket or fd:name.

           inherit duplicates the file descriptor of standard input for
           standard output.

           null connects standard output to /dev/null, i.e. everything
           written to it will be lost.

           tty connects standard output to a tty (as configured via
           TTYPath=, see below). If the TTY is used for output only, the
           executed process will not become the controlling process of the
           terminal, and will not fail or wait for other processes to
           release the terminal.

           journal connects standard output with the journal, which is
           accessible via journalctl(1). Note that everything that is
           written to kmsg (see below) is implicitly stored in the journal
           as well, the specific option listed below is hence a superset of
           this one. (Also note that any external, additional syslog daemons
           receive their log data from the journal, too, hence this is the
           option to use when logging shall be processed with such a
           daemon.)

           kmsg connects standard output with the kernel log buffer which is
           accessible via dmesg(1), in addition to the journal. The journal
           daemon might be configured to send all logs to kmsg anyway, in
           which case this option is no different from journal.

           journal+console and kmsg+console work in a similar way as the two
           options above but copy the output to the system console as well.

           The file:path option may be used to connect a specific file
           system object to standard output. The semantics are similar to
           the same option of StandardInput=, see above. If path refers to a
           regular file on the filesystem, it is opened (created if it
           doesn't exist yet) for writing at the beginning of the file, but
           without truncating it. If standard input and output are directed
           to the same file path, it is opened only once, for reading as
           well as writing and duplicated. This is particularly useful when
           the specified path refers to an AF_UNIX socket in the file
           system, as in that case only a single stream connection is
           created for both input and output.

           append:path is similar to file:path above, but it opens the file
           in append mode.

           socket connects standard output to a socket acquired via socket
           activation. The semantics are similar to the same option of
           StandardInput=, see above.

           The fd:name option connects standard output to a specific, named
           file descriptor provided by a socket unit. A name may be
           specified as part of this option, following a ":" character (e.g.
           "fd:foobar"). If no name is specified, the name "stdout" is
           implied (i.e.  "fd" is equivalent to "fd:stdout"). At least one
           socket unit defining the specified name must be provided via the
           Sockets= option, and the file descriptor name may differ from the
           name of its containing socket unit. If multiple matches are
           found, the first one will be used. See FileDescriptorName= in
           systemd.socket(5) for more details about named descriptors and
           their ordering.

           If the standard output (or error output, see below) of a unit is
           connected to the journal or the kernel log buffer, the unit will
           implicitly gain a dependency of type After= on
           systemd-journald.socket (also see the "Implicit Dependencies"
           section above). Also note that in this case stdout (or stderr,
           see below) will be an AF_UNIX stream socket, and not a pipe or
           FIFO that can be re-opened. This means when executing shell
           scripts the construct echo "hello" > /dev/stderr for writing text
           to stderr will not work. To mitigate this use the construct echo
           "hello" >&2 instead, which is mostly equivalent and avoids this
           pitfall.

           This setting defaults to the value set with
           DefaultStandardOutput= in systemd-system.conf(5), which defaults
           to journal. Note that setting this parameter might result in
           additional dependencies to be added to the unit (see above).

       StandardError=
           Controls where file descriptor 2 (stderr) of the executed
           processes is connected to. The available options are identical to
           those of StandardOutput=, with some exceptions: if set to inherit
           the file descriptor used for standard output is duplicated for
           standard error, while fd:name will use a default file descriptor
           name of "stderr".

           This setting defaults to the value set with DefaultStandardError=
           in systemd-system.conf(5), which defaults to inherit. Note that
           setting this parameter might result in additional dependencies to
           be added to the unit (see above).

       StandardInputText=, StandardInputData=
           Configures arbitrary textual or binary data to pass via file
           descriptor 0 (STDIN) to the executed processes. These settings
           have no effect unless StandardInput= is set to data. Use this
           option to embed process input data directly in the unit file.

           StandardInputText= accepts arbitrary textual data. C-style
           escapes for special characters as well as the usual
           "%"-specifiers are resolved. Each time this setting is used the
           specified text is appended to the per-unit data buffer, followed
           by a newline character (thus every use appends a new line to the
           end of the buffer). Note that leading and trailing whitespace of
           lines configured with this option is removed. If an empty line is
           specified the buffer is cleared (hence, in order to insert an
           empty line, add an additional "\n" to the end or beginning of a
           line).

           StandardInputData= accepts arbitrary binary data, encoded in
           Base64[7]. No escape sequences or specifiers are resolved. Any
           whitespace in the encoded version is ignored during decoding.

           Note that StandardInputText= and StandardInputData= operate on
           the same data buffer, and may be mixed in order to configure both
           binary and textual data for the same input stream. The textual or
           binary data is joined strictly in the order the settings appear
           in the unit file. Assigning an empty string to either will reset
           the data buffer.

           Please keep in mind that in order to maintain readability long
           unit file settings may be split into multiple lines, by suffixing
           each line (except for the last) with a "\" character (see
           systemd.unit(5) for details). This is particularly useful for
           large data configured with these two options. Example:

               ...
               StandardInput=data
               StandardInputData=SWNrIHNpdHplIGRhIHVuJyBlc3NlIEtsb3BzLAp1ZmYgZWVtYWwga2xvcHAncy4KSWNrIGtpZWtl \
                                 LCBzdGF1bmUsIHd1bmRyZSBtaXIsCnVmZiBlZW1hbCBqZWh0IHNlIHVmZiBkaWUgVMO8ci4KTmFu \
                                 dSwgZGVuayBpY2ssIGljayBkZW5rIG5hbnUhCkpldHogaXNzZSB1ZmYsIGVyc2NodCB3YXIgc2Ug \
                                 enUhCkljayBqZWhlIHJhdXMgdW5kIGJsaWNrZSDigJQKdW5kIHdlciBzdGVodCBkcmF1w59lbj8g \
                                 SWNrZSEK
               ...

       LogLevelMax=
           Configures filtering by log level of log messages generated by
           this unit. Takes a syslog log level, one of emerg (lowest log
           level, only highest priority messages), alert, crit, err,
           warning, notice, info, debug (highest log level, also lowest
           priority messages). See syslog(3) for details. By default no
           filtering is applied (i.e. the default maximum log level is
           debug). Use this option to configure the logging system to drop
           log messages of a specific service above the specified level. For
           example, set LogLevelMax=info in order to turn off debug logging
           of a particularly chatty unit. Note that the configured level is
           applied to any log messages written by any of the processes
           belonging to this unit, sent via any supported logging protocol.
           The filtering is applied early in the logging pipeline, before
           any kind of further processing is done. Moreover, messages which
           pass through this filter successfully might still be dropped by
           filters applied at a later stage in the logging subsystem. For
           example, MaxLevelStore= configured in journald.conf(5) might
           prohibit messages of higher log levels to be stored on disk, even
           though the per-unit LogLevelMax= permitted it to be processed.

       LogExtraFields=
           Configures additional log metadata fields to include in all log
           records generated by processes associated with this unit. This
           setting takes one or more journal field assignments in the format
           "FIELD=VALUE" separated by whitespace. See
           systemd.journal-fields(7) for details on the journal field
           concept. Even though the underlying journal implementation
           permits binary field values, this setting accepts only valid
           UTF-8 values. To include space characters in a journal field
           value, enclose the assignment in double quotes (").  The usual
           specifiers are expanded in all assignments (see below). Note that
           this setting is not only useful for attaching additional metadata
           to log records of a unit, but given that all fields and values
           are indexed may also be used to implement cross-unit log record
           matching. Assign an empty string to reset the list.

       LogRateLimitIntervalSec=, LogRateLimitBurst=
           Configures the rate limiting that is applied to messages
           generated by this unit. If, in the time interval defined by
           LogRateLimitIntervalSec=, more messages than specified in
           LogRateLimitBurst= are logged by a service, all further messages
           within the interval are dropped until the interval is over. A
           message about the number of dropped messages is generated. The
           time specification for LogRateLimitIntervalSec= may be specified
           in the following units: "s", "min", "h", "ms", "us" (see
           systemd.time(7) for details). The default settings are set by
           RateLimitIntervalSec= and RateLimitBurst= configured in
           journald.conf(5).

       LogNamespace=
           Run the unit's processes in the specified journal namespace.
           Expects a short user-defined string identifying the namespace. If
           not used the processes of the service are run in the default
           journal namespace, i.e. their log stream is collected and
           processed by systemd-journald.service. If this option is used any
           log data generated by processes of this unit (regardless if via
           the syslog(), journal native logging or stdout/stderr logging) is
           collected and processed by an instance of the
           systemd-journald@.service template unit, which manages the
           specified namespace. The log data is stored in a data store
           independent from the default log namespace's data store. See
           systemd-journald.service(8) for details about journal namespaces.

           Internally, journal namespaces are implemented through Linux
           mount namespacing and over-mounting the directory that contains
           the relevant AF_UNIX sockets used for logging in the unit's mount
           namespace. Since mount namespaces are used this setting
           disconnects propagation of mounts from the unit's processes to
           the host, similar to how ReadOnlyPaths= and similar settings (see
           above) work. Journal namespaces may hence not be used for
           services that need to establish mount points on the host.

           When this option is used the unit will automatically gain
           ordering and requirement dependencies on the two socket units
           associated with the systemd-journald@.service instance so that
           they are automatically established prior to the unit starting up.
           Note that when this option is used log output of this service
           does not appear in the regular journalctl(1) output, unless the
           --namespace= option is used.

           This option is only available for system services and is not
           supported for services running in per-user instances of the
           service manager.

       SyslogIdentifier=
           Sets the process name ("syslog tag") to prefix log lines sent to
           the logging system or the kernel log buffer with. If not set,
           defaults to the process name of the executed process. This option
           is only useful when StandardOutput= or StandardError= are set to
           journal or kmsg (or to the same settings in combination with
           +console) and only applies to log messages written to stdout or
           stderr.

       SyslogFacility=
           Sets the syslog facility identifier to use when logging. One of
           kern, user, mail, daemon, auth, syslog, lpr, news, uucp, cron,
           authpriv, ftp, local0, local1, local2, local3, local4, local5,
           local6 or local7. See syslog(3) for details. This option is only
           useful when StandardOutput= or StandardError= are set to journal
           or kmsg (or to the same settings in combination with +console),
           and only applies to log messages written to stdout or stderr.
           Defaults to daemon.

       SyslogLevel=
           The default syslog log level to use when logging to the logging
           system or the kernel log buffer. One of emerg, alert, crit, err,
           warning, notice, info, debug. See syslog(3) for details. This
           option is only useful when StandardOutput= or StandardError= are
           set to journal or kmsg (or to the same settings in combination
           with +console), and only applies to log messages written to
           stdout or stderr. Note that individual lines output by executed
           processes may be prefixed with a different log level which can be
           used to override the default log level specified here. The
           interpretation of these prefixes may be disabled with
           SyslogLevelPrefix=, see below. For details, see sd-daemon(3).
           Defaults to info.

       SyslogLevelPrefix=
           Takes a boolean argument. If true and StandardOutput= or
           StandardError= are set to journal or kmsg (or to the same
           settings in combination with +console), log lines written by the
           executed process that are prefixed with a log level will be
           processed with this log level set but the prefix removed. If set
           to false, the interpretation of these prefixes is disabled and
           the logged lines are passed on as-is. This only applies to log
           messages written to stdout or stderr. For details about this
           prefixing see sd-daemon(3). Defaults to true.

       TTYPath=
           Sets the terminal device node to use if standard input, output,
           or error are connected to a TTY (see above). Defaults to
           /dev/console.

       TTYReset=
           Reset the terminal device specified with TTYPath= before and
           after execution. Defaults to "no".

       TTYVHangup=
           Disconnect all clients which have opened the terminal device
           specified with TTYPath= before and after execution. Defaults to
           "no".

       TTYVTDisallocate=
           If the terminal device specified with TTYPath= is a virtual
           console terminal, try to deallocate the TTY before and after
           execution. This ensures that the screen and scrollback buffer is
           cleared. Defaults to "no".

SYSTEM V COMPATIBILITY         top

       UtmpIdentifier=
           Takes a four character identifier string for an utmp(5) and wtmp
           entry for this service. This should only be set for services such
           as getty implementations (such as agetty(8)) where utmp/wtmp
           entries must be created and cleared before and after execution,
           or for services that shall be executed as if they were run by a
           getty process (see below). If the configured string is longer
           than four characters, it is truncated and the terminal four
           characters are used. This setting interprets %I style string
           replacements. This setting is unset by default, i.e. no utmp/wtmp
           entries are created or cleaned up for this service.

       UtmpMode=
           Takes one of "init", "login" or "user". If UtmpIdentifier= is
           set, controls which type of utmp(5)/wtmp entries for this service
           are generated. This setting has no effect unless UtmpIdentifier=
           is set too. If "init" is set, only an INIT_PROCESS entry is
           generated and the invoked process must implement a
           getty-compatible utmp/wtmp logic. If "login" is set, first an
           INIT_PROCESS entry, followed by a LOGIN_PROCESS entry is
           generated. In this case, the invoked process must implement a
           login(1)-compatible utmp/wtmp logic. If "user" is set, first an
           INIT_PROCESS entry, then a LOGIN_PROCESS entry and finally a
           USER_PROCESS entry is generated. In this case, the invoked
           process may be any process that is suitable to be run as session
           leader. Defaults to "init".

ENVIRONMENT VARIABLES IN SPAWNED PROCESSES         top

       Processes started by the service manager are executed with an
       environment variable block assembled from multiple sources. Processes
       started by the system service manager generally do not inherit
       environment variables set for the service manager itself (but this
       may be altered via PassEnvironment=), but processes started by the
       user service manager instances generally do inherit all environment
       variables set for the service manager itself.

       For each invoked process the list of environment variables set is
       compiled from the following sources:

       ·   Variables globally configured for the service manager, using the
           DefaultEnvironment= setting in systemd-system.conf(5), the kernel
           command line option systemd.setenv= (see systemd(1)) or via
           systemctl set-environment (see systemctl(1)).

       ·   Variables defined by the service manager itself (see the list
           below)

       ·   Variables set in the service manager's own environment variable
           block (subject to PassEnvironment= for the system service
           manager)

       ·   Variables set via Environment= in the unit file

       ·   Variables read from files specified via EnvironmentFile= in the
           unit file

       ·   Variables set by any PAM modules in case PAMName= is in effect,
           cf. pam_env(8)

       If the same environment variables are set by multiple of these
       sources, the later source — according to the order of the list above
       — wins. Note that as final step all variables listed in
       UnsetEnvironment= are removed again from the compiled environment
       variable list, immediately before it is passed to the executed
       process.

       The following environment variables are set or propagated by the
       service manager for each invoked process:

       $PATH
           Colon-separated list of directories to use when launching
           executables.  systemd uses a fixed value of
           "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin" in the system
           manager. When compiled for systems with "unmerged /usr" (/bin is
           not a symlink to /usr/bin), ":/sbin:/bin" is appended. In case of
           the the user manager, a different path may be configured by the
           distribution. It is recommended to not rely on the order of
           entries, and have only one program with a given name in $PATH.

       $LANG
           Locale. Can be set in locale.conf(5) or on the kernel command
           line (see systemd(1) and kernel-command-line(7)).

       $USER, $LOGNAME, $HOME, $SHELL
           User name (twice), home directory, and the login shell. The
           variables are set for the units that have User= set, which
           includes user systemd instances. See passwd(5).

       $INVOCATION_ID
           Contains a randomized, unique 128bit ID identifying each runtime
           cycle of the unit, formatted as 32 character hexadecimal string.
           A new ID is assigned each time the unit changes from an inactive
           state into an activating or active state, and may be used to
           identify this specific runtime cycle, in particular in data
           stored offline, such as the journal. The same ID is passed to all
           processes run as part of the unit.

       $XDG_RUNTIME_DIR
           The directory to use for runtime objects (such as IPC objects)
           and volatile state. Set for all services run by the user systemd
           instance, as well as any system services that use PAMName= with a
           PAM stack that includes pam_systemd. See below and pam_systemd(8)
           for more information.

       $RUNTIME_DIRECTORY, $STATE_DIRECTORY, $CACHE_DIRECTORY,
       $LOGS_DIRECTORY, $CONFIGURATION_DIRECTORY
           Absolute paths to the directories defined with RuntimeDirectory=,
           StateDirectory=, CacheDirectory=, LogsDirectory=, and
           ConfigurationDirectory= when those settings are used.

       $MAINPID
           The PID of the unit's main process if it is known. This is only
           set for control processes as invoked by ExecReload= and similar.

       $MANAGERPID
           The PID of the user systemd instance, set for processes spawned
           by it.

       $LISTEN_FDS, $LISTEN_PID, $LISTEN_FDNAMES
           Information about file descriptors passed to a service for socket
           activation. See sd_listen_fds(3).

       $NOTIFY_SOCKET
           The socket sd_notify() talks to. See sd_notify(3).

       $WATCHDOG_PID, $WATCHDOG_USEC
           Information about watchdog keep-alive notifications. See
           sd_watchdog_enabled(3).

       $TERM
           Terminal type, set only for units connected to a terminal
           (StandardInput=tty, StandardOutput=tty, or StandardError=tty).
           See termcap(5).

       $LOG_NAMESPACE
           If the LogNamespace= service setting is used, contains name of
           the selected logging namespace.

       $JOURNAL_STREAM
           If the standard output or standard error output of the executed
           processes are connected to the journal (for example, by setting
           StandardError=journal) $JOURNAL_STREAM contains the device and
           inode numbers of the connection file descriptor, formatted in
           decimal, separated by a colon (":"). This permits invoked
           processes to safely detect whether their standard output or
           standard error output are connected to the journal. The device
           and inode numbers of the file descriptors should be compared with
           the values set in the environment variable to determine whether
           the process output is still connected to the journal. Note that
           it is generally not sufficient to only check whether
           $JOURNAL_STREAM is set at all as services might invoke external
           processes replacing their standard output or standard error
           output, without unsetting the environment variable.

           If both standard output and standard error of the executed
           processes are connected to the journal via a stream socket, this
           environment variable will contain information about the standard
           error stream, as that's usually the preferred destination for log
           data. (Note that typically the same stream is used for both
           standard output and standard error, hence very likely the
           environment variable contains device and inode information
           matching both stream file descriptors.)

           This environment variable is primarily useful to allow services
           to optionally upgrade their used log protocol to the native
           journal protocol (using sd_journal_print(3) and other functions)
           if their standard output or standard error output is connected to
           the journal anyway, thus enabling delivery of structured metadata
           along with logged messages.

       $SERVICE_RESULT
           Only defined for the service unit type, this environment variable
           is passed to all ExecStop= and ExecStopPost= processes, and
           encodes the service "result". Currently, the following values are
           defined:

           Table 4. Defined $SERVICE_RESULT values
           ┌──────────────────┬───────────────────────────┐
           │Value             Meaning                   │
           ├──────────────────┼───────────────────────────┤
           │"success"         │ The service ran           │
           │                  │ successfully and exited   │
           │                  │ cleanly.                  │
           ├──────────────────┼───────────────────────────┤
           │"protocol"        │ A protocol violation      │
           │                  │ occurred: the service did │
           │                  │ not take the steps        │
           │                  │ required by its unit      │
           │                  │ configuration             │
           │                  │ (specifically what is     │
           │                  │ configured in its Type=   │
           │                  │ setting).                 │
           ├──────────────────┼───────────────────────────┤
           │"timeout"         │ One of the steps timed    │
           │                  │ out.                      │
           ├──────────────────┼───────────────────────────┤
           │"exit-code"       │ Service process exited    │
           │                  │ with a non-zero exit      │
           │                  │ code; see $EXIT_CODE      │
           │                  │ below for the actual exit │
           │                  │ code returned.            │
           ├──────────────────┼───────────────────────────┤
           │"signal"          │ A service process was     │
           │                  │ terminated abnormally by  │
           │                  │ a signal, without dumping │
           │                  │ core. See $EXIT_CODE      │
           │                  │ below for the actual      │
           │                  │ signal causing the        │
           │                  │ termination.              │
           ├──────────────────┼───────────────────────────┤
           │"core-dump"       │ A service process         │
           │                  │ terminated abnormally     │
           │                  │ with a signal and dumped  │
           │                  │ core. See $EXIT_CODE      │
           │                  │ below for the signal      │
           │                  │ causing the termination.  │
           ├──────────────────┼───────────────────────────┤
           │"watchdog"        │ Watchdog keep-alive ping  │
           │                  │ was enabled for the       │
           │                  │ service, but the deadline │
           │                  │ was missed.               │
           ├──────────────────┼───────────────────────────┤
           │"start-limit-hit" │ A start limit was defined │
           │                  │ for the unit and it was   │
           │                  │ hit, causing the unit to  │
           │                  │ fail to start. See        │
           │                  │ systemd.unit(5)'s         │
           │                  │ StartLimitIntervalSec=    │
           │                  │ and StartLimitBurst= for  │
           │                  │ details.                  │
           ├──────────────────┼───────────────────────────┤
           │"resources"       │ A catch-all condition in  │
           │                  │ case a system operation   │
           │                  │ failed.                   │
           └──────────────────┴───────────────────────────┘
           This environment variable is useful to monitor failure or
           successful termination of a service. Even though this variable is
           available in both ExecStop= and ExecStopPost=, it is usually a
           better choice to place monitoring tools in the latter, as the
           former is only invoked for services that managed to start up
           correctly, and the latter covers both services that failed during
           their start-up and those which failed during their runtime.

       $EXIT_CODE, $EXIT_STATUS
           Only defined for the service unit type, these environment
           variables are passed to all ExecStop=, ExecStopPost= processes
           and contain exit status/code information of the main process of
           the service. For the precise definition of the exit code and
           status, see wait(2).  $EXIT_CODE is one of "exited", "killed",
           "dumped".  $EXIT_STATUS contains the numeric exit code formatted
           as string if $EXIT_CODE is "exited", and the signal name in all
           other cases. Note that these environment variables are only set
           if the service manager succeeded to start and identify the main
           process of the service.

           Table 5. Summary of possible service result variable values
           ┌──────────────────┬──────────────────┬─────────────────────┐
           │$SERVICE_RESULT$EXIT_CODE$EXIT_STATUS        │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"success"         │ "killed"         │ "HUP", "INT",       │
           │                  │                  │ "TERM", "PIPE"      │
           │                  ├──────────────────┼─────────────────────┤
           │                  │ "exited"         │ "0"                 │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"protocol"        │ not set          │ not set             │
           │                  ├──────────────────┼─────────────────────┤
           │                  │ "exited"         │ "0"                 │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"timeout"         │ "killed"         │ "TERM", "KILL"      │
           │                  ├──────────────────┼─────────────────────┤
           │                  │ "exited"         │ "0", "1", "2", "3", │
           │                  │                  │ ..., "255"          │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"exit-code"       │ "exited"         │ "1", "2", "3", ..., │
           │                  │                  │ "255"               │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"signal"          │ "killed"         │ "HUP", "INT",       │
           │                  │                  │ "KILL", ...         │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"core-dump"       │ "dumped"         │ "ABRT", "SEGV",     │
           │                  │                  │ "QUIT", ...         │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"watchdog"        │ "dumped"         │ "ABRT"              │
           │                  ├──────────────────┼─────────────────────┤
           │                  │ "killed"         │ "TERM", "KILL"      │
           │                  ├──────────────────┼─────────────────────┤
           │                  │ "exited"         │ "0", "1", "2", "3", │
           │                  │                  │ ..., "255"          │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"exec-condition"  │ "exited"         │ "1", "2", "3", "4", │
           │                  │                  │ ..., "254"          │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"oom-kill"        │ "killed"         │ "TERM", "KILL"      │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"start-limit-hit" │ not set          │ not set             │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"resources"       │ any of the above │ any of the above    │
           ├──────────────────┴──────────────────┴─────────────────────┤
           │Note: the process may be also terminated by a signal not   │
           │sent by systemd. In particular the process may send an     │
           │arbitrary signal to itself in a handler for any of the     │
           │non-maskable signals. Nevertheless, in the "timeout" and   │
           │"watchdog" rows above only the signals that systemd sends  │
           │have been included. Moreover, using SuccessExitStatus=     │
           │additional exit statuses may be declared to indicate       │
           │clean termination, which is not reflected by this table.   │
           └───────────────────────────────────────────────────────────┘

       $PIDFILE
           The path to the configured PID file, in case the process is
           forked off on behalf of a service that uses the PIDFile= setting,
           see systemd.service(5) for details. Service code may use this
           environment variable to automatically generate a PID file at the
           location configured in the unit file. This field is set to an
           absolute path in the file system.

       For system services, when PAMName= is enabled and pam_systemd is part
       of the selected PAM stack, additional environment variables defined
       by systemd may be set for services. Specifically, these are
       $XDG_SEAT, $XDG_VTNR, see pam_systemd(8) for details.

PROCESS EXIT CODES         top

       When invoking a unit process the service manager possibly fails to
       apply the execution parameters configured with the settings above. In
       that case the already created service process will exit with a
       non-zero exit code before the configured command line is executed.
       (Or in other words, the child process possibly exits with these error
       codes, after having been created by the fork(2) system call, but
       before the matching execve(2) system call is called.) Specifically,
       exit codes defined by the C library, by the LSB specification and by
       the systemd service manager itself are used.

       The following basic service exit codes are defined by the C library.

       Table 6. Basic C library exit codes
       ┌──────────┬───────────────┬────────────────────┐
       │Exit Code Symbolic Name Description        │
       ├──────────┼───────────────┼────────────────────┤
       │0         │ EXIT_SUCCESS  │ Generic success    │
       │          │               │ code.              │
       ├──────────┼───────────────┼────────────────────┤
       │1         │ EXIT_FAILURE  │ Generic failure or │
       │          │               │ unspecified error. │
       └──────────┴───────────────┴────────────────────┘

       The following service exit codes are defined by the LSB
       specification[8].

       Table 7. LSB service exit codes
       ┌──────────┬──────────────────────┬────────────────────┐
       │Exit Code Symbolic Name        Description        │
       ├──────────┼──────────────────────┼────────────────────┤
       │2         │ EXIT_INVALIDARGUMENT │ Invalid or excess  │
       │          │                      │ arguments.         │
       ├──────────┼──────────────────────┼────────────────────┤
       │3         │ EXIT_NOTIMPLEMENTED  │ Unimplemented      │
       │          │                      │ feature.           │
       ├──────────┼──────────────────────┼────────────────────┤
       │4         │ EXIT_NOPERMISSION    │ The user has       │
       │          │                      │ insufficient       │
       │          │                      │ privileges.        │
       ├──────────┼──────────────────────┼────────────────────┤
       │5         │ EXIT_NOTINSTALLED    │ The program is not │
       │          │                      │ installed.         │
       ├──────────┼──────────────────────┼────────────────────┤
       │6         │ EXIT_NOTCONFIGURED   │ The program is not │
       │          │                      │ configured.        │
       ├──────────┼──────────────────────┼────────────────────┤
       │7         │ EXIT_NOTRUNNING      │ The program is not │
       │          │                      │ running.           │
       └──────────┴──────────────────────┴────────────────────┘

       The LSB specification suggests that error codes 200 and above are
       reserved for implementations. Some of them are used by the service
       manager to indicate problems during process invocation:

       Table 8. systemd-specific exit codes
       ┌──────────┬──────────────────────────────┬─────────────────────────────────────────────┐
       │Exit Code Symbolic Name                Description                                 │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │200       │ EXIT_CHDIR                   │ Changing to the                             │
       │          │                              │ requested working                           │
       │          │                              │ directory failed.                           │
       │          │                              │ See                                         │
       │          │                              │ WorkingDirectory=                           │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │201       │ EXIT_NICE                    │ Failed to set up                            │
       │          │                              │ process scheduling                          │
       │          │                              │ priority (nice                              │
       │          │                              │ level). See Nice=                           │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │202       │ EXIT_FDS                     │ Failed to close                             │
       │          │                              │ unwanted file                               │
       │          │                              │ descriptors, or to                          │
       │          │                              │ adjust passed file                          │
       │          │                              │ descriptors.                                │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │203       │ EXIT_EXEC                    │ The actual process                          │
       │          │                              │ execution failed                            │
       │          │                              │ (specifically, the                          │
       │          │                              │ execve(2) system                            │
       │          │                              │ call). Most likely                          │
       │          │                              │ this is caused by a                         │
       │          │                              │ missing or                                  │
       │          │                              │ non-accessible                              │
       │          │                              │ executable file.                            │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │204       │ EXIT_MEMORY                  │ Failed to perform                           │
       │          │                              │ an action due to                            │
       │          │                              │ memory shortage.                            │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │205       │ EXIT_LIMITS                  │ Failed to adjust                            │
       │          │                              │ resource limits.                            │
       │          │                              │ See LimitCPU= and                           │
       │          │                              │ related settings                            │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │206       │ EXIT_OOM_ADJUST              │ Failed to adjust                            │
       │          │                              │ the OOM setting.                            │
       │          │                              │ See OOMScoreAdjust=                         │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │207       │ EXIT_SIGNAL_MASK             │ Failed to set                               │
       │          │                              │ process signal                              │
       │          │                              │ mask.                                       │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │208       │ EXIT_STDIN                   │ Failed to set up                            │
       │          │                              │ standard input. See                         │
       │          │                              │ StandardInput=                              │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │209       │ EXIT_STDOUT                  │ Failed to set up                            │
       │          │                              │ standard output.                            │
       │          │                              │ See StandardOutput=                         │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │210       │ EXIT_CHROOT                  │ Failed to change                            │
       │          │                              │ root directory (‐                           │
       │          │                              │ chroot(2)). See                             │
       │          │                              │ RootDirectory=/RootImage=                   │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │211       │ EXIT_IOPRIO                  │ Failed to set up IO                         │
       │          │                              │ scheduling priority. See                    │
       │          │                              │ IOSchedulingClass=/IOSchedulingPriority=    │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │212       │ EXIT_TIMERSLACK              │ Failed to set up timer slack. See           │
       │          │                              │ TimerSlackNSec= above.                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │213       │ EXIT_SECUREBITS              │ Failed to set process secure bits. See      │
       │          │                              │ SecureBits= above.                          │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │214       │ EXIT_SETSCHEDULER            │ Failed to set up CPU scheduling. See        │
       │          │                              │ CPUSchedulingPolicy=/CPUSchedulingPriority= │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │215       │ EXIT_CPUAFFINITY             │ Failed to set up CPU affinity. See          │
       │          │                              │ CPUAffinity= above.                         │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │216       │ EXIT_GROUP                   │ Failed to determine or change group         │
       │          │                              │ credentials. See                            │
       │          │                              │ Group=/SupplementaryGroups= above.          │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │217       │ EXIT_USER                    │ Failed to determine or change user          │
       │          │                              │ credentials, or to set up user namespacing. │
       │          │                              │ See User=/PrivateUsers= above.              │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │218       │ EXIT_CAPABILITIES            │ Failed to drop capabilities, or apply       │
       │          │                              │ ambient capabilities. See                   │
       │          │                              │ CapabilityBoundingSet=/AmbientCapabilities= │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │219       │ EXIT_CGROUP                  │ Setting up the service control group        │
       │          │                              │ failed.                                     │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │220       │ EXIT_SETSID                  │ Failed to create new process session.       │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │221       │ EXIT_CONFIRM                 │ Execution has been cancelled by the user.   │
       │          │                              │ See the systemd.confirm_spawn= kernel       │
       │          │                              │ command line setting on                     │
       │          │                              │ kernel-command-line(7) for details.         │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │222       │ EXIT_STDERR                  │ Failed to set up standard error output. See │
       │          │                              │ StandardError= above.                       │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │224       │ EXIT_PAM                     │ Failed to set up PAM session. See PAMName=  │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │225       │ EXIT_NETWORK                 │ Failed to set up network namespacing. See   │
       │          │                              │ PrivateNetwork= above.                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │226       │ EXIT_NAMESPACE               │ Failed to set up mount namespacing. See     │
       │          │                              │ ReadOnlyPaths= and related settings above.  │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │227       │ EXIT_NO_NEW_PRIVILEGES       │ Failed to disable new privileges. See       │
       │          │                              │ NoNewPrivileges=yes above.                  │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │228       │ EXIT_SECCOMP                 │ Failed to apply system call filters. See    │
       │          │                              │ SystemCallFilter= and related settings      │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │229       │ EXIT_SELINUX_CONTEXT         │ Determining or changing SELinux context     │
       │          │                              │ failed. See SELinuxContext= above.          │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │230       │ EXIT_PERSONALITY             │ Failed to set up an execution domain        │
       │          │                              │ (personality). See Personality= above.      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │231       │ EXIT_APPARMOR_PROFILE        │ Failed to prepare changing AppArmor         │
       │          │                              │ profile. See AppArmorProfile= above.        │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │232       │ EXIT_ADDRESS_FAMILIES        │ Failed to restrict address families. See    │
       │          │                              │ RestrictAddressFamilies= above.             │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │233       │ EXIT_RUNTIME_DIRECTORY       │ Setting up runtime directory failed. See    │
       │          │                              │ RuntimeDirectory= and related settings      │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │235       │ EXIT_CHOWN                   │ Failed to adjust socket ownership. Used for │
       │          │                              │ socket units only.                          │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │236       │ EXIT_SMACK_PROCESS_LABEL     │ Failed to set SMACK label. See              │
       │          │                              │ SmackProcessLabel= above.                   │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │237       │ EXIT_KEYRING                 │ Failed to set up kernel keyring.            │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │238       │ EXIT_STATE_DIRECTORY         │ Failed to set up unit's state directory.    │
       │          │                              │ See StateDirectory= above.                  │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │239       │ EXIT_CACHE_DIRECTORY         │ Failed to set up unit's cache directory.    │
       │          │                              │ See CacheDirectory= above.                  │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │240       │ EXIT_LOGS_DIRECTORY          │ Failed to set up unit's logging directory.  │
       │          │                              │ See LogsDirectory= above.                   │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │241       │ EXIT_CONFIGURATION_DIRECTORY │ Failed to set up unit's configuration       │
       │          │                              │ directory. See ConfigurationDirectory=      │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │242       │ EXIT_NUMA_POLICY             │ Failed to set up unit's NUMA memory policy. │
       │          │                              │ See NUMAPolicy= and NUMAMask= above.        │
       └──────────┴──────────────────────────────┴─────────────────────────────────────────────┘

       Finally, the BSD operating systems define a set of exit codes,
       typically defined on Linux systems too:

       Table 9. BSD exit codes
       ┌──────────┬────────────────┬─────────────────────┐
       │Exit Code Symbolic Name  Description         │
       ├──────────┼────────────────┼─────────────────────┤
       │64        │ EX_USAGE       │ Command line usage  │
       │          │                │ error               │
       ├──────────┼────────────────┼─────────────────────┤
       │65        │ EX_DATAERR     │ Data format error   │
       ├──────────┼────────────────┼─────────────────────┤
       │66        │ EX_NOINPUT     │ Cannot open input   │
       ├──────────┼────────────────┼─────────────────────┤
       │67        │ EX_NOUSER      │ Addressee unknown   │
       ├──────────┼────────────────┼─────────────────────┤
       │68        │ EX_NOHOST      │ Host name unknown   │
       ├──────────┼────────────────┼─────────────────────┤
       │69        │ EX_UNAVAILABLE │ Service unavailable │
       ├──────────┼────────────────┼─────────────────────┤
       │70        │ EX_SOFTWARE    │ internal software   │
       │          │                │ error               │
       ├──────────┼────────────────┼─────────────────────┤
       │71        │ EX_OSERR       │ System error (e.g., │
       │          │                │ can't fork)         │
       ├──────────┼────────────────┼─────────────────────┤
       │72        │ EX_OSFILE      │ Critical OS file    │
       │          │                │ missing             │
       ├──────────┼────────────────┼─────────────────────┤
       │73        │ EX_CANTCREAT   │ Can't create (user) │
       │          │                │ output file         │
       ├──────────┼────────────────┼─────────────────────┤
       │74        │ EX_IOERR       │ Input/output error  │
       ├──────────┼────────────────┼─────────────────────┤
       │75        │ EX_TEMPFAIL    │ Temporary failure;  │
       │          │                │ user is invited to  │
       │          │                │ retry               │
       ├──────────┼────────────────┼─────────────────────┤
       │76        │ EX_PROTOCOL    │ Remote error in     │
       │          │                │ protocol            │
       ├──────────┼────────────────┼─────────────────────┤
       │77        │ EX_NOPERM      │ Permission denied   │
       ├──────────┼────────────────┼─────────────────────┤
       │78        │ EX_CONFIG      │ Configuration error │
       └──────────┴────────────────┴─────────────────────┘

SEE ALSO         top

       systemd(1), systemctl(1), systemd-analyze(1), journalctl(1),
       systemd-system.conf(5), systemd.unit(5), systemd.service(5),
       systemd.socket(5), systemd.swap(5), systemd.mount(5),
       systemd.kill(5), systemd.resource-control(5), systemd.time(7),
       systemd.directives(7), tmpfiles.d(5), exec(3)

NOTES         top

        1. Discoverable Partitions Specification
           https://systemd.io/DISCOVERABLE_PARTITIONS

        2. User/Group Name Syntax
           https://systemd.io/USER_NAMES

        3. No New Privileges Flag
           https://www.kernel.org/doc/html/latest/userspace-api/no_new_privs.html

        4. proc.txt
           https://www.kernel.org/doc/Documentation/filesystems/proc.txt

        5. C escapes
           https://en.wikipedia.org/wiki/Escape_sequences_in_C#Table_of_escape_sequences

        6. most control characters
           https://en.wikipedia.org/wiki/Control_character#In_ASCII

        7. Base64
           https://tools.ietf.org/html/rfc2045#section-6.8

        8. LSB specification
           https://refspecs.linuxbase.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/iniscrptact.html

COLOPHON         top

       This page is part of the systemd (systemd system and service manager)
       project.  Information about the project can be found at 
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have a bug
       report for this manual page, see
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.  This
       page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2020-08-13.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2020-08-11.)  If you discover any rendering problems in
       this HTML version of the page, or you believe there is a better or
       more up-to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not part
       of the original manual page), send a mail to man-pages@man7.org

systemd 246                                                  SYSTEMD.EXEC(5)

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