systemd.socket(5) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | AUTOMATIC DEPENDENCIES | OPTIONS | SEE ALSO | NOTES | COLOPHON

SYSTEMD.SOCKET(5)            systemd.socket            SYSTEMD.SOCKET(5)

NAME         top

       systemd.socket - Socket unit configuration

SYNOPSIS         top

       socket.socket

DESCRIPTION         top

       A unit configuration file whose name ends in ".socket" encodes
       information about an IPC or network socket or a file system FIFO
       controlled and supervised by systemd, for socket-based
       activation.

       This man page lists the configuration options specific to this
       unit type. See systemd.unit(5) for the common options of all unit
       configuration files. The common configuration items are
       configured in the generic [Unit] and [Install] sections. The
       socket specific configuration options are configured in the
       [Socket] section.

       Additional options are listed in systemd.exec(5), which define
       the execution environment the ExecStartPre=, ExecStartPost=,
       ExecStopPre= and ExecStopPost= commands are executed in, and in
       systemd.kill(5), which define the way the processes are
       terminated, and in systemd.resource-control(5), which configure
       resource control settings for the processes of the socket.

       For each socket unit, a matching service unit must exist,
       describing the service to start on incoming traffic on the socket
       (see systemd.service(5) for more information about .service
       units). The name of the .service unit is by default the same as
       the name of the .socket unit, but can be altered with the
       Service= option described below. Depending on the setting of the
       Accept= option described below, this .service unit must either be
       named like the .socket unit, but with the suffix replaced, unless
       overridden with Service=; or it must be a template unit named the
       same way. Example: a socket file foo.socket needs a matching
       service foo.service if Accept=no is set. If Accept=yes is set, a
       service template foo@.service must exist from which services are
       instantiated for each incoming connection.

       No implicit WantedBy= or RequiredBy= dependency from the socket
       to the service is added. This means that the service may be
       started without the socket, in which case it must be able to open
       sockets by itself. To prevent this, an explicit Requires=
       dependency may be added.

       Socket units may be used to implement on-demand starting of
       services, as well as parallelized starting of services. See the
       blog stories linked at the end for an introduction.

       Note that the daemon software configured for socket activation
       with socket units needs to be able to accept sockets from
       systemd, either via systemd's native socket passing interface
       (see sd_listen_fds(3) for details about the precise protocol used
       and the order in which the file descriptors are passed) or via
       traditional inetd(8)-style socket passing (i.e. sockets passed in
       via standard input and output, using StandardInput=socket in the
       service file).

       All network sockets allocated through .socket units are allocated
       in the host's network namespace (see network_namespaces(7)). This
       does not mean however that the service activated by a configured
       socket unit has to be part of the host's network namespace as
       well. It is supported and even good practice to run services in
       their own network namespace (for example through PrivateNetwork=,
       see systemd.exec(5)), receiving only the sockets configured
       through socket-activation from the host's namespace. In such a
       set-up communication within the host's network namespace is only
       permitted through the activation sockets passed in while all
       sockets allocated from the service code itself will be associated
       with the service's own namespace, and thus possibly subject to a
       restrictive configuration.

AUTOMATIC DEPENDENCIES         top

   Implicit Dependencies
       The following dependencies are implicitly added:

       •   Socket units automatically gain a Before= dependency on the
           service units they activate.

       •   Socket units referring to file system paths (such as AF_UNIX
           sockets or FIFOs) implicitly gain Requires= and After=
           dependencies on all mount units necessary to access those
           paths.

       •   Socket units using the BindToDevice= setting automatically
           gain a BindsTo= and After= dependency on the device unit
           encapsulating the specified network interface.

       Additional implicit dependencies may be added as result of
       execution and resource control parameters as documented in
       systemd.exec(5) and systemd.resource-control(5).

   Default Dependencies
       The following dependencies are added unless
       DefaultDependencies=no is set:

       •   Socket units automatically gain a Before= dependency on
           sockets.target.

       •   Socket units automatically gain a pair of After= and
           Requires= dependency on sysinit.target, and a pair of Before=
           and Conflicts= dependencies on shutdown.target. These
           dependencies ensure that the socket unit is started before
           normal services at boot, and is stopped on shutdown. Only
           sockets involved with early boot or late system shutdown
           should disable DefaultDependencies= option.

OPTIONS         top

       Socket files must include a [Socket] section, which carries
       information about the socket or FIFO it supervises. A number of
       options that may be used in this section are shared with other
       unit types. These options are documented in systemd.exec(5) and
       systemd.kill(5). The options specific to the [Socket] section of
       socket units are the following:

       ListenStream=, ListenDatagram=, ListenSequentialPacket=
           Specifies an address to listen on for a stream (SOCK_STREAM),
           datagram (SOCK_DGRAM), or sequential packet (SOCK_SEQPACKET)
           socket, respectively. The address can be written in various
           formats:

           If the address starts with a slash ("/"), it is read as file
           system socket in the AF_UNIX socket family.

           If the address starts with an at symbol ("@"), it is read as
           abstract namespace socket in the AF_UNIX family. The "@" is
           replaced with a NUL character before binding. For details,
           see unix(7).

           If the address string is a single number, it is read as port
           number to listen on via IPv6. Depending on the value of
           BindIPv6Only= (see below) this might result in the service
           being available via both IPv6 and IPv4 (default) or just via
           IPv6.

           If the address string is a string in the format "v.w.x.y:z",
           it is interpreted as IPv4 address v.w.x.y and port z.

           If the address string is a string in the format "[x]:y", it
           is interpreted as IPv6 address x and port y. An optional
           interface scope (interface name or number) may be specified
           after a "%" symbol: "[x]:y%dev". Interface scopes are only
           useful with link-local addresses, because the kernel ignores
           them in other cases. Note that if an address is specified as
           IPv6, it might still make the service available via IPv4 too,
           depending on the BindIPv6Only= setting (see below).

           If the address string is a string in the format "vsock:x:y",
           it is read as CID x on a port y address in the AF_VSOCK
           family. The CID is a unique 32-bit integer identifier in
           AF_VSOCK analogous to an IP address. Specifying the CID is
           optional, and may be set to the empty string.

           Note that SOCK_SEQPACKET (i.e.  ListenSequentialPacket=) is
           only available for AF_UNIX sockets.  SOCK_STREAM (i.e.
           ListenStream=) when used for IP sockets refers to TCP
           sockets, SOCK_DGRAM (i.e.  ListenDatagram=) to UDP.

           These options may be specified more than once, in which case
           incoming traffic on any of the sockets will trigger service
           activation, and all listed sockets will be passed to the
           service, regardless of whether there is incoming traffic on
           them or not. If the empty string is assigned to any of these
           options, the list of addresses to listen on is reset, all
           prior uses of any of these options will have no effect.

           It is also possible to have more than one socket unit for the
           same service when using Service=, and the service will
           receive all the sockets configured in all the socket units.
           Sockets configured in one unit are passed in the order of
           configuration, but no ordering between socket units is
           specified.

           If an IP address is used here, it is often desirable to
           listen on it before the interface it is configured on is up
           and running, and even regardless of whether it will be up and
           running at any point. To deal with this, it is recommended to
           set the FreeBind= option described below.

       ListenFIFO=
           Specifies a file system FIFO (see fifo(7) for details) to
           listen on. This expects an absolute file system path as
           argument. Behavior otherwise is very similar to the
           ListenDatagram= directive above.

       ListenSpecial=
           Specifies a special file in the file system to listen on.
           This expects an absolute file system path as argument.
           Behavior otherwise is very similar to the ListenFIFO=
           directive above. Use this to open character device nodes as
           well as special files in /proc/ and /sys/.

       ListenNetlink=
           Specifies a Netlink family to create a socket for to listen
           on. This expects a short string referring to the AF_NETLINK
           family name (such as audit or kobject-uevent) as argument,
           optionally suffixed by a whitespace followed by a multicast
           group integer. Behavior otherwise is very similar to the
           ListenDatagram= directive above.

       ListenMessageQueue=
           Specifies a POSIX message queue name to listen on (see
           mq_overview(7) for details). This expects a valid message
           queue name (i.e. beginning with "/"). Behavior otherwise is
           very similar to the ListenFIFO= directive above. On Linux
           message queue descriptors are actually file descriptors and
           can be inherited between processes.

       ListenUSBFunction=
           Specifies a USB FunctionFS[1] endpoints location to listen
           on, for implementation of USB gadget functions. This expects
           an absolute file system path of a FunctionFS mount point as
           the argument. Behavior otherwise is very similar to the
           ListenFIFO= directive above. Use this to open the FunctionFS
           endpoint ep0. When using this option, the activated service
           has to have the USBFunctionDescriptors= and
           USBFunctionStrings= options set.

       SocketProtocol=
           Takes one of udplite or sctp. The socket will use the
           UDP-Lite (IPPROTO_UDPLITE) or SCTP (IPPROTO_SCTP) protocol,
           respectively.

       BindIPv6Only=
           Takes one of default, both or ipv6-only. Controls the
           IPV6_V6ONLY socket option (see ipv6(7) for details). If both,
           IPv6 sockets bound will be accessible via both IPv4 and IPv6.
           If ipv6-only, they will be accessible via IPv6 only. If
           default (which is the default, surprise!), the system wide
           default setting is used, as controlled by
           /proc/sys/net/ipv6/bindv6only, which in turn defaults to the
           equivalent of both.

       Backlog=
           Takes an unsigned integer argument. Specifies the number of
           connections to queue that have not been accepted yet. This
           setting matters only for stream and sequential packet
           sockets. See listen(2) for details. Defaults to SOMAXCONN
           (128).

       BindToDevice=
           Specifies a network interface name to bind this socket to. If
           set, traffic will only be accepted from the specified network
           interfaces. This controls the SO_BINDTODEVICE socket option
           (see socket(7) for details). If this option is used, an
           implicit dependency from this socket unit on the network
           interface device unit is created (see systemd.device(5)).
           Note that setting this parameter might result in additional
           dependencies to be added to the unit (see above).

       SocketUser=, SocketGroup=
           Takes a UNIX user/group name. When specified, all AF_UNIX
           sockets and FIFO nodes in the file system are owned by the
           specified user and group. If unset (the default), the nodes
           are owned by the root user/group (if run in system context)
           or the invoking user/group (if run in user context). If only
           a user is specified but no group, then the group is derived
           from the user's default group.

       SocketMode=
           If listening on a file system socket or FIFO, this option
           specifies the file system access mode used when creating the
           file node. Takes an access mode in octal notation. Defaults
           to 0666.

       DirectoryMode=
           If listening on a file system socket or FIFO, the parent
           directories are automatically created if needed. This option
           specifies the file system access mode used when creating
           these directories. Takes an access mode in octal notation.
           Defaults to 0755.

       Accept=
           Takes a boolean argument. If yes, a service instance is
           spawned for each incoming connection and only the connection
           socket is passed to it. If no, all listening sockets
           themselves are passed to the started service unit, and only
           one service unit is spawned for all connections (also see
           above). This value is ignored for datagram sockets and FIFOs
           where a single service unit unconditionally handles all
           incoming traffic. Defaults to no. For performance reasons, it
           is recommended to write new daemons only in a way that is
           suitable for Accept=no. A daemon listening on an AF_UNIX
           socket may, but does not need to, call close(2) on the
           received socket before exiting. However, it must not unlink
           the socket from a file system. It should not invoke
           shutdown(2) on sockets it got with Accept=no, but it may do
           so for sockets it got with Accept=yes set. Setting Accept=yes
           is mostly useful to allow daemons designed for usage with
           inetd(8) to work unmodified with systemd socket activation.

           For IPv4 and IPv6 connections, the REMOTE_ADDR environment
           variable will contain the remote IP address, and REMOTE_PORT
           will contain the remote port. This is the same as the format
           used by CGI. For SOCK_RAW, the port is the IP protocol.

       Writable=
           Takes a boolean argument. May only be used in conjunction
           with ListenSpecial=. If true, the specified special file is
           opened in read-write mode, if false, in read-only mode.
           Defaults to false.

       FlushPending=
           Takes a boolean argument. May only be used when Accept=no. If
           yes, the socket's buffers are cleared after the triggered
           service exited. This causes any pending data to be flushed
           and any pending incoming connections to be rejected. If no,
           the socket's buffers won't be cleared, permitting the service
           to handle any pending connections after restart, which is the
           usually expected behaviour. Defaults to no.

       MaxConnections=
           The maximum number of connections to simultaneously run
           services instances for, when Accept=yes is set. If more
           concurrent connections are coming in, they will be refused
           until at least one existing connection is terminated. This
           setting has no effect on sockets configured with Accept=no or
           datagram sockets. Defaults to 64.

       MaxConnectionsPerSource=
           The maximum number of connections for a service per source IP
           address. This is very similar to the MaxConnections=
           directive above. Disabled by default.

       KeepAlive=
           Takes a boolean argument. If true, the TCP/IP stack will send
           a keep alive message after 2h (depending on the configuration
           of /proc/sys/net/ipv4/tcp_keepalive_time) for all TCP streams
           accepted on this socket. This controls the SO_KEEPALIVE
           socket option (see socket(7) and the TCP Keepalive HOWTO[2]
           for details.) Defaults to false.

       KeepAliveTimeSec=
           Takes time (in seconds) as argument. The connection needs to
           remain idle before TCP starts sending keepalive probes. This
           controls the TCP_KEEPIDLE socket option (see socket(7) and
           the TCP Keepalive HOWTO[2] for details.) Defaults value is
           7200 seconds (2 hours).

       KeepAliveIntervalSec=
           Takes time (in seconds) as argument between individual
           keepalive probes, if the socket option SO_KEEPALIVE has been
           set on this socket. This controls the TCP_KEEPINTVL socket
           option (see socket(7) and the TCP Keepalive HOWTO[2] for
           details.) Defaults value is 75 seconds.

       KeepAliveProbes=
           Takes an integer as argument. It is the number of
           unacknowledged probes to send before considering the
           connection dead and notifying the application layer. This
           controls the TCP_KEEPCNT socket option (see socket(7) and the
           TCP Keepalive HOWTO[2] for details.) Defaults value is 9.

       NoDelay=
           Takes a boolean argument. TCP Nagle's algorithm works by
           combining a number of small outgoing messages, and sending
           them all at once. This controls the TCP_NODELAY socket option
           (see tcp(7)). Defaults to false.

       Priority=
           Takes an integer argument controlling the priority for all
           traffic sent from this socket. This controls the SO_PRIORITY
           socket option (see socket(7) for details.).

       DeferAcceptSec=
           Takes time (in seconds) as argument. If set, the listening
           process will be awakened only when data arrives on the
           socket, and not immediately when connection is established.
           When this option is set, the TCP_DEFER_ACCEPT socket option
           will be used (see tcp(7)), and the kernel will ignore initial
           ACK packets without any data. The argument specifies the
           approximate amount of time the kernel should wait for
           incoming data before falling back to the normal behavior of
           honoring empty ACK packets. This option is beneficial for
           protocols where the client sends the data first (e.g. HTTP,
           in contrast to SMTP), because the server process will not be
           woken up unnecessarily before it can take any action.

           If the client also uses the TCP_DEFER_ACCEPT option, the
           latency of the initial connection may be reduced, because the
           kernel will send data in the final packet establishing the
           connection (the third packet in the "three-way handshake").

           Disabled by default.

       ReceiveBuffer=, SendBuffer=
           Takes an integer argument controlling the receive or send
           buffer sizes of this socket, respectively. This controls the
           SO_RCVBUF and SO_SNDBUF socket options (see socket(7) for
           details.). The usual suffixes K, M, G are supported and are
           understood to the base of 1024.

       IPTOS=
           Takes an integer argument controlling the IP Type-Of-Service
           field for packets generated from this socket. This controls
           the IP_TOS socket option (see ip(7) for details.). Either a
           numeric string or one of low-delay, throughput, reliability
           or low-cost may be specified.

       IPTTL=
           Takes an integer argument controlling the IPv4
           Time-To-Live/IPv6 Hop-Count field for packets generated from
           this socket. This sets the IP_TTL/IPV6_UNICAST_HOPS socket
           options (see ip(7) and ipv6(7) for details.)

       Mark=
           Takes an integer value. Controls the firewall mark of packets
           generated by this socket. This can be used in the firewall
           logic to filter packets from this socket. This sets the
           SO_MARK socket option. See iptables(8) for details.

       ReusePort=
           Takes a boolean value. If true, allows multiple bind(2)s to
           this TCP or UDP port. This controls the SO_REUSEPORT socket
           option. See socket(7) for details.

       SmackLabel=, SmackLabelIPIn=, SmackLabelIPOut=
           Takes a string value. Controls the extended attributes
           "security.SMACK64", "security.SMACK64IPIN" and
           "security.SMACK64IPOUT", respectively, i.e. the security
           label of the FIFO, or the security label for the incoming or
           outgoing connections of the socket, respectively. See
           Smack.txt[3] for details.

       SELinuxContextFromNet=
           Takes a boolean argument. When true, systemd will attempt to
           figure out the SELinux label used for the instantiated
           service from the information handed by the peer over the
           network. Note that only the security level is used from the
           information provided by the peer. Other parts of the
           resulting SELinux context originate from either the target
           binary that is effectively triggered by socket unit or from
           the value of the SELinuxContext= option. This configuration
           option applies only when activated service is passed in
           single socket file descriptor, i.e. service instances that
           have standard input connected to a socket or services
           triggered by exactly one socket unit. Also note that this
           option is useful only when MLS/MCS SELinux policy is
           deployed. Defaults to "false".

       PipeSize=
           Takes a size in bytes. Controls the pipe buffer size of FIFOs
           configured in this socket unit. See fcntl(2) for details. The
           usual suffixes K, M, G are supported and are understood to
           the base of 1024.

       MessageQueueMaxMessages=, MessageQueueMessageSize=
           These two settings take integer values and control the
           mq_maxmsg field or the mq_msgsize field, respectively, when
           creating the message queue. Note that either none or both of
           these variables need to be set. See mq_setattr(3) for
           details.

       FreeBind=
           Takes a boolean value. Controls whether the socket can be
           bound to non-local IP addresses. This is useful to configure
           sockets listening on specific IP addresses before those IP
           addresses are successfully configured on a network interface.
           This sets the IP_FREEBIND/IPV6_FREEBIND socket option. For
           robustness reasons it is recommended to use this option
           whenever you bind a socket to a specific IP address. Defaults
           to false.

       Transparent=
           Takes a boolean value. Controls the
           IP_TRANSPARENT/IPV6_TRANSPARENT socket option. Defaults to
           false.

       Broadcast=
           Takes a boolean value. This controls the SO_BROADCAST socket
           option, which allows broadcast datagrams to be sent from this
           socket. Defaults to false.

       PassCredentials=
           Takes a boolean value. This controls the SO_PASSCRED socket
           option, which allows AF_UNIX sockets to receive the
           credentials of the sending process in an ancillary message.
           Defaults to false.

       PassSecurity=
           Takes a boolean value. This controls the SO_PASSSEC socket
           option, which allows AF_UNIX sockets to receive the security
           context of the sending process in an ancillary message.
           Defaults to false.

       PassPacketInfo=
           Takes a boolean value. This controls the IP_PKTINFO,
           IPV6_RECVPKTINFO, NETLINK_PKTINFO or PACKET_AUXDATA socket
           options, which enable reception of additional per-packet
           metadata as ancillary message, on AF_INET, AF_INET6, AF_UNIX
           and AF_PACKET sockets. Defaults to false.

       Timestamping=
           Takes one of "off", "us" (alias: "usec", "µs") or "ns"
           (alias: "nsec"). This controls the SO_TIMESTAMP or
           SO_TIMESTAMPNS socket options, and enables whether ingress
           network traffic shall carry timestamping metadata. Defaults
           to off.

       TCPCongestion=
           Takes a string value. Controls the TCP congestion algorithm
           used by this socket. Should be one of "westwood", "veno",
           "cubic", "lp" or any other available algorithm supported by
           the IP stack. This setting applies only to stream sockets.

       ExecStartPre=, ExecStartPost=
           Takes one or more command lines, which are executed before or
           after the listening sockets/FIFOs are created and bound,
           respectively. The first token of the command line must be an
           absolute filename, then followed by arguments for the
           process. Multiple command lines may be specified following
           the same scheme as used for ExecStartPre= of service unit
           files.

       ExecStopPre=, ExecStopPost=
           Additional commands that are executed before or after the
           listening sockets/FIFOs are closed and removed, respectively.
           Multiple command lines may be specified following the same
           scheme as used for ExecStartPre= of service unit files.

       TimeoutSec=
           Configures the time to wait for the commands specified in
           ExecStartPre=, ExecStartPost=, ExecStopPre= and ExecStopPost=
           to finish. If a command does not exit within the configured
           time, the socket will be considered failed and be shut down
           again. All commands still running will be terminated forcibly
           via SIGTERM, and after another delay of this time with
           SIGKILL. (See KillMode= in systemd.kill(5).) Takes a
           unit-less value in seconds, or a time span value such as
           "5min 20s". Pass "0" to disable the timeout logic. Defaults
           to DefaultTimeoutStartSec= from the manager configuration
           file (see systemd-system.conf(5)).

       Service=
           Specifies the service unit name to activate on incoming
           traffic. This setting is only allowed for sockets with
           Accept=no. It defaults to the service that bears the same
           name as the socket (with the suffix replaced). In most cases,
           it should not be necessary to use this option. Note that
           setting this parameter might result in additional
           dependencies to be added to the unit (see above).

       RemoveOnStop=
           Takes a boolean argument. If enabled, any file nodes created
           by this socket unit are removed when it is stopped. This
           applies to AF_UNIX sockets in the file system, POSIX message
           queues, FIFOs, as well as any symlinks to them configured
           with Symlinks=. Normally, it should not be necessary to use
           this option, and is not recommended as services might
           continue to run after the socket unit has been terminated and
           it should still be possible to communicate with them via
           their file system node. Defaults to off.

       Symlinks=
           Takes a list of file system paths. The specified paths will
           be created as symlinks to the AF_UNIX socket path or FIFO
           path of this socket unit. If this setting is used, only one
           AF_UNIX socket in the file system or one FIFO may be
           configured for the socket unit. Use this option to manage one
           or more symlinked alias names for a socket, binding their
           lifecycle together. Note that if creation of a symlink fails
           this is not considered fatal for the socket unit, and the
           socket unit may still start. If an empty string is assigned,
           the list of paths is reset. Defaults to an empty list.

       FileDescriptorName=
           Assigns a name to all file descriptors this socket unit
           encapsulates. This is useful to help activated services
           identify specific file descriptors, if multiple fds are
           passed. Services may use the sd_listen_fds_with_names(3) call
           to acquire the names configured for the received file
           descriptors. Names may contain any ASCII character, but must
           exclude control characters and ":", and must be at most 255
           characters in length. If this setting is not used, the file
           descriptor name defaults to the name of the socket unit,
           including its .socket suffix.

       TriggerLimitIntervalSec=, TriggerLimitBurst=
           Configures a limit on how often this socket unit my be
           activated within a specific time interval. The
           TriggerLimitIntervalSec= may be used to configure the length
           of the time interval in the usual time units "us", "ms", "s",
           "min", "h", ... and defaults to 2s (See systemd.time(7) for
           details on the various time units understood). The
           TriggerLimitBurst= setting takes a positive integer value and
           specifies the number of permitted activations per time
           interval, and defaults to 200 for Accept=yes sockets (thus by
           default permitting 200 activations per 2s), and 20 otherwise
           (20 activations per 2s). Set either to 0 to disable any form
           of trigger rate limiting. If the limit is hit, the socket
           unit is placed into a failure mode, and will not be
           connectible anymore until restarted. Note that this limit is
           enforced before the service activation is enqueued.

       Check systemd.exec(5) and systemd.kill(5) for more settings.

SEE ALSO         top

       systemd(1), systemctl(1), systemd-system.conf(5),
       systemd.unit(5), systemd.exec(5), systemd.kill(5),
       systemd.resource-control(5), systemd.service(5),
       systemd.directives(7), sd_listen_fds(3),
       sd_listen_fds_with_names(3)

       For more extensive descriptions see the "systemd for Developers"
       series: Socket Activation[4], Socket Activation, part II[5],
       Converting inetd Services[6], Socket Activated Internet Services
       and OS Containers[7].

NOTES         top

        1. USB FunctionFS
           https://www.kernel.org/doc/Documentation/usb/functionfs.txt

        2. TCP Keepalive HOWTO
           http://www.tldp.org/HOWTO/html_single/TCP-Keepalive-HOWTO/

        3. Smack.txt
           https://www.kernel.org/doc/Documentation/security/Smack.txt

        4. Socket Activation
           http://0pointer.de/blog/projects/socket-activation.html

        5. Socket Activation, part II
           http://0pointer.de/blog/projects/socket-activation2.html

        6. Converting inetd Services
           http://0pointer.de/blog/projects/inetd.html

        7. Socket Activated Internet Services and OS Containers
           http://0pointer.de/blog/projects/socket-activated-containers.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 2021-08-27.  (At that
       time, the date of the most recent commit that was found in the
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systemd 249                                            SYSTEMD.SOCKET(5)

Pages that refer to this page: systemctl(1)systemd(1)systemd-socket-activate(1)sd-daemon(3)sd_is_fifo(3)sd_listen_fds(3)systemd.exec(5)systemd.kill(5)systemd.resource-control(5)systemd.service(5)systemd.unit(5)daemon(7)systemd.special(7)systemd.syntax(7)systemd-journal-remote.service(8)systemd-socket-proxyd(8)