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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT | EXAMPLES | EXIT STATUS | SEE ALSO | NOTES | COLOPHON |
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SYSTEMD-VMSPAWN(1) systemd-vmspawn SYSTEMD-VMSPAWN(1)
systemd-vmspawn - Spawn an OS in a virtual machine
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.
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
machine.
Added in version 255.
Host Configuration
--cpus=CPUS
The number of CPUs to start the virtual machine with. Defaults
to 1.
Added in version 255.
--ram=BYTES
The amount of memory to start the virtual machine with.
Defaults to 2G.
Added in version 255.
--kvm=BOOL
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.
--vsock=BOOL
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.
--vsock-cid=CID
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.
--tpm=BOOL
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
used.
Added in version 256.
--tpm-state=PATH|auto|off
Configures where to place TPM state, in case TPM support is
enabled (see --tpm= above). This takes an absolute file system
path to a directory to persistently place the state in. If the
directory is missing it is created as needed. If set to the
special string "auto" a persistent path is automatically
derived from the VM image path or directory path, with the
".tpmstate" suffix appended. If set to the special string
"off" the TPM state is only maintained transiently and flushed
out when the VM shuts down. This mode is not suitable for VMs
which lock disk encryption keys to the TPM, as these keys will
be lost on every reboot. Defaults to "auto".
Added in version 258.
--linux=PATH
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.
--initrd=PATH
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
/usr/lib/systemd/network/80-vm-vt.network.
Added in version 255.
--network-user-mode
Use user mode networking.
Added in version 255.
--firmware=PATH
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.
--discard-disk=BOOL
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.
--secure-boot=BOOL
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.
--grow-image=BYTES, -G BYTES
Grows the image file specified by --image= to the specified
size in bytes if it is smaller. Executes no operation if no
image file is used or the image file is already as large or
larger than requested. The specified size accepts the usual K,
M, G suffixes (to the base of 1024). Specified values are
rounded up to multiples of 4096.
Added in version 258.
--smbios11=STRING, -s STRING
Passes the specified string into the VM as an SMBIOS Type #11
vendor string. This is useful to parameterize the invoked VM
in various ways. See smbios-type-11(7) for details.
Added in version 258.
--notify-ready=
Configures support for notifications from the VM's init
process to systemd-vmspawn. If true, systemd-vmspawn will
consider the machine as ready only when it has received a
"READY=1" message from the init process in the VM. If false,
systemd-vmspawn will consider the machine as ready immediately
after creation. In either case, systemd-vmspawn sends its own
readiness notification to its manager after the spawned VM is
ready. For more details about notifications see sd_notify(3).
Defaults to true. (Note that this is unlike the option of the
same name to systemd-vmspawn(1) that defaults to false.)
Added in version 258.
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.
--uuid=
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
-S, --slice=
Make the VM part of the specified slice, instead of the
default machine.slice. This applies only if the machine is run
in its own scope unit, i.e. if --keep-unit is not used.
Added in version 258.
--property=
Set a unit property on the scope unit to register for the
machine. This applies only if the machine is run in its own
scope unit, i.e. if --keep-unit is not used. Takes unit
property assignments in the same format as systemctl
set-property. This is useful to set memory limits and similar
for the VM.
Added in version 258.
--register=
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
--private-users=UID_SHIFT[:UID_RANGE]
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.
--extra-drive=PATH
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-journal=FILE|DIR
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
systemd-journal-remote(8).
Added in version 256.
--pass-ssh-key=BOOL
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.
--ssh-key-type=TYPE
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(8).
Added in version 256.
Input/Output Options
--console=MODE
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.
--background=COLOR
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.
Credentials
--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.
Other
--no-pager
Do not pipe output into a pager.
-h, --help
Print a short help text and exit.
--version
Print a short version string and exit.
--no-ask-password
Do not query the user for authentication for privileged
operations.
$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
Pager to use when --no-pager is not given. $SYSTEMD_PAGER is
used if set; otherwise $PAGER is used. If neither
$SYSTEMD_PAGER nor $PAGER are set, a set of well-known pager
implementations is tried in turn, including less(1) and
more(1), until one is found. If no pager implementation is
discovered, no pager is invoked. Setting those environment
variables to an empty string or the value "cat" is equivalent
to passing --no-pager.
Note: if $SYSTEMD_PAGERSECURE is not set, $SYSTEMD_PAGER and
$PAGER can only be used to disable the pager (with "cat" or
""), and are otherwise 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
Common pager commands like less(1), in addition to "paging",
i.e. scrolling through the output, support opening of or
writing to other files and running arbitrary shell commands.
When commands are invoked with elevated privileges, for
example under sudo(8) or pkexec(1), the pager becomes a
security boundary. Care must be taken that only programs with
strictly limited functionality are used as pagers, and
unintended interactive features like opening or creation of
new files or starting of subprocesses are not allowed. "Secure
mode" for the pager may be enabled as described below, if the
pager supports that (most pagers are not written in a way that
takes this into consideration). It is recommended to either
explicitly enable "secure mode" or to completely disable the
pager using --no-pager or PAGER=cat when allowing untrusted
users to execute commands with elevated privileges.
This option takes a boolean argument. When set to true, the
"secure mode" of the pager is enabled. In "secure mode",
LESSSECURE=1 will be set when invoking the pager, which
instructs the pager to disable commands that open or create
new files or start new subprocesses. Currently only less(1) is
known to understand this variable and implement "secure mode".
When set to false, no limitation is placed on the pager.
Setting SYSTEMD_PAGERSECURE=0 or not removing it from the
inherited environment may allow the user to invoke arbitrary
commands.
When $SYSTEMD_PAGERSECURE is not set, systemd tools attempt to
automatically figure out if "secure mode" should be enabled
and whether the pager supports it. "Secure mode" is enabled if
the effective UID is not the same as the owner of the login
session, see geteuid(2) and sd_pid_get_owner_uid(3), or when
running under sudo(8) or similar tools ($SUDO_UID is set [3]).
In those cases, SYSTEMD_PAGERSECURE=1 will be set and pagers
which are not known to implement "secure mode" will not be
used at all. Note that this autodetection only covers the most
common mechanisms to elevate privileges and is intended as
convenience. It is recommended to explicitly set
$SYSTEMD_PAGERSECURE or disable the pager.
Note that if the $SYSTEMD_PAGER or $PAGER variables are to be
honoured, other than to disable the pager,
$SYSTEMD_PAGERSECURE must be set too.
$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 42 Cloud image using machinectl
$ curl -L \
-O https://download.fedoraproject.org/pub/fedora/linux/releases/42/Cloud/x86_64/images/Fedora-Cloud-Base-42-1.1.x86_64.raw.xz \
-O https://download.fedoraproject.org/pub/fedora/linux/releases/42/Cloud/x86_64/images/Fedora-Cloud-42-1.1-x86_64-CHECKSUM \
-O https://fedoraproject.org/fedora.gpg
$ gpgv --keyring ./fedora.gpg Fedora-Cloud-42-1.1-x86_64-CHECKSUM
$ sha256sum -c Fedora-Cloud-42-1.1-x86_64-CHECKSUM
# machinectl import-raw Fedora-Cloud-Base-42-1.1.x86_64.raw.xz fedora-42-cloud
# systemd-vmspawn -M fedora-42-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 is not 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
3. It is recommended for other tools to set and check $SUDO_UID
as appropriate, treating it is a common interface.
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 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) 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 258~rc2 SYSTEMD-VMSPAWN(1)
Pages that refer to this page: importctl(1), machinectl(1), systemd-nspawn(1), systemd-vmspawn(1), systemd.directives(7), systemd.index(7), systemd-import-generator(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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