systemd-vmspawn(1) — Linux manual page


SYSTEMD-VMSPAWN(1)           systemd-vmspawn          SYSTEMD-VMSPAWN(1)

NAME         top

       systemd-vmspawn - Spawn an OS in a virtual machine

SYNOPSIS         top

       systemd-vmspawn [OPTIONS...] [ARGS...]

DESCRIPTION         top

       systemd-vmspawn may be used to start a virtual machine from an OS
       image. In many ways it is similar to systemd-nspawn(1), but
       launches a full virtual machine instead of using namespaces.

       File descriptors for /dev/kvm and /dev/vhost-vsock can be passed
       to systemd-vmspawn 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), these
       file descriptors must be passed with the names "kvm" and
       "vhost-vsock" respectively.

       Note: on Ubuntu/Debian derivatives systemd-vmspawn requires the
       user to be in the "kvm" group to use the VSOCK options.

OPTIONS         top

       The excess arguments are passed as extra kernel command line
       arguments using SMBIOS.

       The following options are understood:

       -q, --quiet
           Turns off any status output by the tool itself. When this
           switch is used, the only output from vmspawn will be the
           console output of the Virtual Machine OS itself.

           Added in version 256.

   Image Options
       -D, --directory=
           Directory to use as file system root for the virtual machine.

           One of either --directory= or --image= must be specified. If
           neither are specified --directory=.  is assumed.

           Note: If mounting a non-root owned directory you may require
           --private-users= to map into the user's subuid namespace. An
           example of how to use /etc/subuid for this is given later.

           Added in version 256.

       -i, --image=
           Root file system disk image (or device node) for the virtual

           Added in version 255.

   Host Configuration
           The number of CPUs to start the virtual machine with.
           Defaults to 1.

           Added in version 255.

           The amount of memory to start the virtual machine with.
           Defaults to 2G.

           Added in version 255.

           If --kvm= is not specified KVM support will be detected
           automatically. If true, KVM is always used, and if false, KVM
           is never used.

           Added in version 255.

           If --vsock= is not specified VSOCK networking support will be
           detected automatically. If true, VSOCK networking is always
           used, and if false, VSOCK networking is never used.

           Added in version 255.

           Sets the specific CID to use for the guest. Valid CIDs are in
           the range 3 to 4294967294 (0xFFFF_FFFE). CIDs outside of this
           range are reserved. By default vmspawn will attempt to derive
           a CID for the guest derived from the machine name, falling
           back to a random CID if this CID is taken.

           Added in version 255.

           If --tpm= is not specified vmspawn will detect the presence
           of swtpm(8) and use it if available. If yes is specified
           swtpm(8) is always used, and if no is set swtpm(8) is never

           Note: the virtual TPM used may change in future.

           Added in version 256.

           Set the linux kernel image to use for direct kernel boot. If
           a directory type image is used and --linux= was omitted,
           vmspawn will search for boot loader entries according to the
           Boot Loader Specification[1] assuming XBOOTLDR to be located
           at /boot and ESP to be /efi respectively. If no kernel was
           installed into the image then the image will fail to boot.

           Added in version 256.

           Set the initrd to use for direct kernel boot. If the --linux=
           supplied is a Boot Loader Specification[1] Type #2 entry,
           then this argument is not required. If no initrd was
           installed into the image then the image will fail to boot.

           --initrd= can be specified multiple times and vmspawn will
           merge them together.

           Added in version 256.

       -n, --network-tap
           Create a TAP device to network with the virtual machine.

           Note: root privileges are required to use TAP networking.
           Additionally, systemd-networkd(8) must be running and
           correctly set up on the host to provision the host interface.
           The relevant ".network" file can be found at

           Added in version 255.

           Use user mode networking.

           Added in version 255.

           Takes an absolute path, or a relative path beginning with ./.
           Specifies a JSON firmware definition file, which allows
           selecting the firmware to boot in the VM. If not specified a
           suitable firmware is automatically discovered. If the special
           string "list" is specified lists all discovered firmwares.

           Added in version 256.

           Controls whether qemu processes discard requests from the VM.
           This prevents long running VMs from using more disk space
           than required. This is enabled by default.

           Added in version 256.

           Configure whether to search for firmware which supports
           Secure Boot.

           If the option is not specified the first firmware which is
           detected will be used. If the option is set to yes then the
           first firmware with Secure Boot support will be selected. If
           no is specified then the first firmware without Secure Boot
           will be selected.

           Added in version 255.

   System Identity Options
       -M, --machine=
           Sets the machine name for this virtual machine. This name may
           be used to identify this virtual machine during its runtime
           (for example in tools like machinectl(1) and similar).

           Added in version 255.

           Set the specified UUID for the virtual machine. The init
           system will initialize /etc/machine-id from this if this file
           is not set yet. Note that this option takes effect only if
           /etc/machine-id in the virtual machine is unpopulated.

           Added in version 256.

   Property Options
           Controls whether the virtual machine is registered with
           systemd-machined(8). Takes a boolean argument, which defaults
           to "yes" when running as root, and "no" when running as a
           regular user. This ensures that the virtual machine is
           accessible via machinectl(1).

           Note: root privileges are required to use this option as
           registering with systemd-machined(8) requires privileged
           D-Bus method calls.

           Added in version 256.

   User Namespacing Options
           Controls user namespacing under --directory=. If enabled,
           virtiofsd(1) is instructed to map user and group ids (UIDs
           and GIDs). This involves mapping the private UIDs/GIDs used
           in the virtual machine (starting with the virtual machine's
           root user 0 and up) to a range of UIDs/GIDs on the host that
           are not used for other purposes (usually in the range beyond
           the host's UID/GID 65536).

           If one or two colon-separated numbers are specified, user
           namespacing is turned on.  UID_SHIFT specifies the first host
           UID/GID to map, UID_RANGE is optional and specifies number of
           host UIDs/GIDs to assign to the virtual machine. If UID_RANGE
           is omitted, 65536 UIDs/GIDs are assigned.

           When user namespaces are used, the GID range assigned to each
           virtual machine is always chosen identical to the UID range.

           Added in version 256.

   Mount Options
       --bind=PATH, --bind-ro=PATH
           Mount a directory from the host into the virtual machine.
           Takes one of: a path argument — in which case the specified
           path will be mounted from the host to the same path in the
           virtual machine, or a colon-separated pair of paths — in
           which case the first specified path is the source in the
           host, and the second path is the destination in the virtual
           machine. If the source path is not absolute, it is resolved
           relative to the current working directory. The --bind-ro=
           option creates read-only bind mounts. Backslash escapes are
           interpreted, so "\:" may be used to embed colons in either
           path. This option may be specified multiple times for
           creating multiple independent bind mount points.

           Added in version 256.

           Takes a disk image or block device on the host and supplies
           it to the virtual machine as another drive.

           Added in version 256.

   Integration Options
           Forward the virtual machine's journal to the host.
           systemd-journal-remote(8) is currently used to receive the
           guest VM's forwarded journal entries. This option determines
           where this journal is saved on the host and has the same
           semantics as -o/--output described in

           Added in version 256.

           By default an SSH key is generated to allow systemd-vmspawn
           to open a D-Bus connection to the VM's systemd bus. Setting
           this to "no" will disable SSH key generation.

           The generated keys are ephemeral. That is they are valid only
           for the current invocation of systemd-vmspawn, and are
           typically not persisted.

           Added in version 256.

           Configures the type of SSH key to generate, see ssh-keygen(1)
           for more information.

           By default "ed25519" keys are generated, however "rsa" keys
           may also be useful if the VM has a particularly old version
           of sshd.

           Added in version 256.

   Input/Output Options
           Configures how to set up the console of the VM. Takes one of
           "interactive", "read-only", "native", "gui". Defaults to
           "interactive".  "interactive" provides an interactive
           terminal interface to the VM.  "read-only" is similar, but is
           strictly read-only, i.e. does not accept any input from the
           user.  "native" also provides a TTY-based interface, but uses
           qemu native implementation (which means the qemu monitor is
           available).  "gui" shows the qemu graphical UI.

           Added in version 256.

           Change the terminal background color to the specified ANSI
           color as long as the VM runs. The color specified should be
           an ANSI X3.64 SGR background color, i.e. strings such as
           "40", "41", ..., "47", "48;2;...", "48;5;...". See ANSI
           Escape Code (Wikipedia)[2] for details. Assign an empty
           string to disable any coloring. This only has an effect in
           --console=interactive and --console=read-only modes.

           Added in version 256.

       --load-credential=ID:PATH, --set-credential=ID:VALUE
           Pass a credential to the virtual machine. These two options
           correspond to the LoadCredential= and SetCredential= settings
           in unit files. See systemd.exec(5) for details about these
           concepts, as well as the syntax of the option's arguments.

           In order to embed binary data into the credential data for
           --set-credential=, use C-style escaping (i.e.  "\n" to embed
           a newline, or "\x00" to embed a NUL byte). Note that the
           invoking shell might already apply unescaping once, hence
           this might require double escaping!

           Added in version 255.

           Do not pipe output into a pager.

       -h, --help
           Print a short help text and exit.

           Print a short version string and exit.

ENVIRONMENT         top

           The maximum log level of emitted messages (messages with a
           higher log level, i.e. less important ones, will be
           suppressed). Takes a comma-separated list of values. A value
           may be either one of (in order of decreasing importance)
           emerg, alert, crit, err, warning, notice, info, debug, or an
           integer in the range 0...7. See syslog(3) for more
           information. Each value may optionally be prefixed with one
           of console, syslog, kmsg or journal followed by a colon to
           set the maximum log level for that specific log target (e.g.
           SYSTEMD_LOG_LEVEL=debug,console:info specifies to log at
           debug level except when logging to the console which should
           be at info level). Note that the global maximum log level
           takes priority over any per target maximum log levels.

           A boolean. If true, messages written to the tty will be
           colored according to priority.

           This setting is only useful when messages are written
           directly to the terminal, because journalctl(1) and other
           tools that display logs will color messages based on the log
           level on their own.

           A boolean. If true, console log messages will be prefixed
           with a timestamp.

           This setting is only useful when messages are written
           directly to the terminal or a file, because journalctl(1) and
           other tools that display logs will attach timestamps based on
           the entry metadata on their own.

           A boolean. If true, messages will be prefixed with a filename
           and line number in the source code where the message

           Note that the log location is often attached as metadata to
           journal entries anyway. Including it directly in the message
           text can nevertheless be convenient when debugging programs.

           A boolean. If true, messages will be prefixed with the
           current numerical thread ID (TID).

           Note that the this information is attached as metadata to
           journal entries anyway. Including it directly in the message
           text can nevertheless be convenient when debugging programs.

           The destination for log messages. One of console (log to the
           attached tty), console-prefixed (log to the attached tty but
           with prefixes encoding the log level and "facility", see
           syslog(3), kmsg (log to the kernel circular log buffer),
           journal (log to the journal), journal-or-kmsg (log to the
           journal if available, and to kmsg otherwise), auto (determine
           the appropriate log target automatically, the default), null
           (disable log output).

           Whether to ratelimit kmsg or not. Takes a boolean. Defaults
           to "true". If disabled, systemd will not ratelimit messages
           written to kmsg.

           Pager to use when --no-pager is not given; overrides $PAGER.
           If neither $SYSTEMD_PAGER nor $PAGER are set, a set of
           well-known pager implementations are tried in turn, including
           less(1) and more(1), until one is found. If no pager
           implementation is discovered no pager is invoked. Setting
           this environment variable to an empty string or the value
           "cat" is equivalent to passing --no-pager.

           Note: if $SYSTEMD_PAGERSECURE is not set, $SYSTEMD_PAGER (as
           well as $PAGER) will be silently ignored.

           Override the options passed to less (by default "FRSXMK").

           Users might want to change two options in particular:

               This option instructs the pager to exit immediately when
               Ctrl+C is pressed. To allow less to handle Ctrl+C itself
               to switch back to the pager command prompt, unset this

               If the value of $SYSTEMD_LESS does not include "K", and
               the pager that is invoked is less, Ctrl+C will be ignored
               by the executable, and needs to be handled by the pager.

               This option instructs the pager to not send termcap
               initialization and deinitialization strings to the
               terminal. It is set by default to allow command output to
               remain visible in the terminal even after the pager
               exits. Nevertheless, this prevents some pager
               functionality from working, in particular paged output
               cannot be scrolled with the mouse.

           Note that setting the regular $LESS environment variable has
           no effect for less invocations by systemd tools.

           See less(1) for more discussion.

           Override the charset passed to less (by default "utf-8", if
           the invoking terminal is determined to be UTF-8 compatible).

           Note that setting the regular $LESSCHARSET environment
           variable has no effect for less invocations by systemd tools.

           Takes a boolean argument. When true, the "secure" mode of the
           pager is enabled; if false, disabled. If $SYSTEMD_PAGERSECURE
           is not set at all, secure mode is enabled if the effective
           UID is not the same as the owner of the login session, see
           geteuid(2) and sd_pid_get_owner_uid(3). In secure mode,
           LESSSECURE=1 will be set when invoking the pager, and the
           pager shall disable commands that open or create new files or
           start new subprocesses. When $SYSTEMD_PAGERSECURE is not set
           at all, pagers which are not known to implement secure mode
           will not be used. (Currently only less(1) implements secure

           Note: when commands are invoked with elevated privileges, for
           example under sudo(8) or pkexec(1), care must be taken to
           ensure that unintended interactive features are not enabled.
           "Secure" mode for the pager may be enabled automatically as
           describe above. Setting SYSTEMD_PAGERSECURE=0 or not removing
           it from the inherited environment allows the user to invoke
           arbitrary commands. Note that if the $SYSTEMD_PAGER or $PAGER
           variables are to be honoured, $SYSTEMD_PAGERSECURE must be
           set too. It might be reasonable to completely disable the
           pager using --no-pager instead.

           Takes a boolean argument. When true, systemd and related
           utilities will use colors in their output, otherwise the
           output will be monochrome. Additionally, the variable can
           take one of the following special values: "16", "256" to
           restrict the use of colors to the base 16 or 256 ANSI colors,
           respectively. This can be specified to override the automatic
           decision based on $TERM and what the console is connected to.

           The value must be a boolean. Controls whether clickable links
           should be generated in the output for terminal emulators
           supporting this. This can be specified to override the
           decision that systemd makes based on $TERM and other

EXAMPLES         top

       Example 1. Run an Arch Linux VM image generated by mkosi

           $ mkosi -d arch -p systemd -p linux --autologin -o image.raw -f build
           $ systemd-vmspawn --image=image.raw

       Example 2. Import and run a Fedora 39 Cloud image using

           $ curl -L \
                  -O \
                  -O \
           $ gpgv --keyring ./fedora.gpg Fedora-Cloud-40-1.10-x86_64-CHECKSUM
           $ sha256sum -c Fedora-Cloud-40-1.10-x86_64-CHECKSUM
           # machinectl import-raw Fedora-Cloud-Base-40-1.10.x86_64.raw.xz fedora-40-cloud
           # systemd-vmspawn -M fedora-40-cloud

       Example 3. Build and run systemd's system image and forward the
       VM's journal to a local file

           $ mkosi build
           $ systemd-vmspawn \
               -D mkosi.output/system \
               --private-users $(grep $(whoami) /etc/subuid | cut -d: -f2) \
               --linux mkosi.output/system.efi \
               --forward-journal=vm.journal \

       Note: this example also uses a kernel command line argument to
       ensure SELinux isn't started in enforcing mode.

       Example 4. SSH into a running VM using systemd-ssh-proxy

           $ mkosi build
           $ my_vsock_cid=3735928559
           $ systemd-vmspawn \
               -D mkosi.output/system \
               --private-users $(grep $(whoami) /etc/subuid | cut -d: -f2) \
               --linux mkosi.output/system.efi \
               --vsock-cid $my_vsock_cid \
           $ ssh root@vsock/$my_vsock_cid -i /run/user/$UID/systemd/vmspawn/machine-*-system-ed25519

EXIT STATUS         top

       If an error occurred the value errno is propagated to the return
       code. If EXIT_STATUS is supplied by the running image that is
       returned. Otherwise EXIT_SUCCESS is returned.

SEE ALSO         top

       systemd(1), mkosi(1), machinectl(1), importctl(1), Boot Loader

NOTES         top

        1. Boot Loader Specification

        2. ANSI Escape Code (Wikipedia)

COLOPHON         top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨⟩.  If you have
       a bug report for this manual page, see
       This page was obtained from the project's upstream Git repository
       ⟨⟩ on 2024-06-14.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2024-06-13.)  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

systemd 257~devel                                     SYSTEMD-VMSPAWN(1)

Pages that refer to this page: importctl(1)machinectl(1)systemd.directives(7)systemd.index(7)