systemd-vmspawn - Man Page

systemd-vmspawn [Options...] [ARGS...]

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.

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.

$SYSTEMD_LOG_LEVEL

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.

$SYSTEMD_LOG_COLOR

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.

$SYSTEMD_LOG_TIME

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.

$SYSTEMD_LOG_LOCATION

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

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.

$SYSTEMD_LOG_TID

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.

$SYSTEMD_LOG_TARGET

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).

$SYSTEMD_LOG_RATELIMIT_KMSG

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

$SYSTEMD_PAGER

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.

$SYSTEMD_LESS

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

Users might want to change two options in particular:

K

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 option.

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.

X

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.

$SYSTEMD_LESSCHARSET

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.

$SYSTEMD_PAGERSECURE

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 mode.)

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.

$SYSTEMD_COLORS

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.

$SYSTEMD_URLIFY

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 conditions.

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 machinectl

$ curl -L \
       -O https://download.fedoraproject.org/pub/fedora/linux/releases/40/Cloud/x86_64/images/Fedora-Cloud-Base-40-1.10.x86_64.raw.xz \
       -O https://download.fedoraproject.org/pub/fedora/linux/releases/40/Cloud/x86_64/images/Fedora-Cloud-40-1.10-x86_64-CHECKSUM \
       -O https://fedoraproject.org/fedora.gpg
$ 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 \
    enforcing=0

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 \
    enforcing=0
$ ssh root@vsock/$my_vsock_cid -i /run/user/$UID/systemd/vmspawn/machine-*-system-ed25519

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.

systemd(1), mkosi(1), machinectl(1), importctl(1), Boot Loader Specification^[1]

1. Boot Loader Specification
   https://uapi-group.org/specifications/specs/boot_loader_specification
2. ANSI Escape Code (Wikipedia)
   https://en.wikipedia.org/wiki/ANSI_escape_code#SGR_(Select_Graphic_Rendition)_parameters

importctl(1), machinectl(1), systemd.directives(7), systemd.index(7).