systemd-nspawn may be used to run a command or OS in a light-weight
namespace container. In many ways it is similar to chroot(1), but
more powerful since it fully virtualizes the file system hierarchy,
as well as the process tree, the various IPC subsystems and the host
and domain name.
systemd-nspawn limits access to various kernel interfaces in the
container to read-only, such as /sys, /proc/sys or /sys/fs/selinux.
Network interfaces and the system clock may not be changed from
within the container. Device nodes may not be created. The host
system cannot be rebooted and kernel modules may not be loaded from
within the container.
Note that even though these security precautions are taken
systemd-nspawn is not suitable for secure container setups. Many of
the security features may be circumvented and are hence primarily
useful to avoid accidental changes to the host system from the
container. The intended use of this program is debugging and testing
as well as building of packages, distributions and software involved
with boot and systems management.
In contrast to chroot(1)systemd-nspawn may be used to boot full
Linux-based operating systems in a container.
Use a tool like yum(8), debootstrap(8), or pacman(8) to set up an OS
directory tree suitable as file system hierarchy for systemd-nspawn
Note that systemd-nspawn will mount file systems private to the
container to /dev, /run and similar. These will not be visible
outside of the container, and their contents will be lost when the
Note that running two systemd-nspawn containers from the same
directory tree will not make processes in them see each other. The
PID namespace separation of the two containers is complete and the
containers will share very few runtime objects except for the
underlying file system. Use machinectl(1)'s login command to request
an additional login prompt in a running container.
systemd-nspawn implements the Container Interface specification.
As a safety check systemd-nspawn will verify the existence of
/usr/lib/os-release or /etc/os-release in the container tree before
starting the container (see os-release(5)). It might be necessary to
add this file to the container tree manually if the OS of the
container is too old to contain this file out-of-the-box.
If option -b is specified, the arguments are used as arguments for
the init binary. Otherwise, COMMAND specifies the program to launch
in the container, and the remaining arguments are used as arguments
for this program. If -b is not used and no arguments are specifed, a
shell is launched in the container.
The following options are understood:
Directory to use as file system root for the container. If
neither --directory= nor --image= are specified, the current
directory will be used. May not be specified together with
Disk image to mount the root directory for the container from.
Takes a path to a regular file or to a block device node. The
file or block device must contain a GUID Partition Table with a
root partition which is mounted as the root directory of the
container. Optionally, it may contain a home and/or a server data
partition which are mounted to the appropriate places in the
container. All these partitions must be identified by the
partition types defined by the Discoverable PartitionsSpecification. Any other partitions, such as foreign
partitions, swap partitions or EFI system partitions are not
mounted. May not be specified together with --directory=.
Automatically search for an init binary and invoke it instead of
a shell or a user supplied program. If this option is used,
arguments specified on the command line are used as arguments for
the init binary. This option may not be combined with
After transitioning into the container, change to the specified
user-defined in the container's user database. Like all other
systemd-nspawn features, this is not a security feature and
provides protection against accidental destructive operations
Sets the machine name for this container. This name may be used
to identify this container on the host, and is used to initialize
the container's hostname (which the container can choose to
override, however). If not specified, the last component of the
root directory of the container is used.
Set the specified UUID for the container. The init system will
initialize /etc/machine-id from this if this file is not set yet.
Make the container part of the specified slice, instead of the
Disconnect networking of the container from the host. This makes
all network interfaces unavailable in the container, with the
exception of the loopback device and those specified with
--network-interface= and configured with --network-veth. If this
option is specified, the CAP_NET_ADMIN capability will be added
to the set of capabilities the container retains. The latter may
be disabled by using --drop-capability=.
Assign the specified network interface to the container. This
will remove the specified interface from the calling namespace
and place it in the container. When the container terminates, it
is moved back to the host namespace. Note that
--network-interface= implies --private-network. This option may
be used more than once to add multiple network interfaces to the
Create a "macvlan" interface of the specified Ethernet network
interface and add it to the container. A "macvlan" interface is a
virtual interface that adds a second MAC address to an existing
physical Ethernet link. The interface in the container will be
named after the interface on the host, prefixed with "mv-". Note
that --network-macvlan= implies --private-network. This option
may be used more than once to add multiple network interfaces to
Create a virtual Ethernet link ("veth") between host and
container. The host side of the Ethernet link will be available
as a network interface named after the container's name (as
specified with --machine=), prefixed with "ve-". The container
side of the Ethernet link will be named "host0". Note that
--network-veth implies --private-network.
Adds the host side of the Ethernet link created with
--network-veth to the specified bridge. Note that
--network-bridge= implies --network-veth. If this option is used,
the host side of the Ethernet link will use the "vb-" prefix
instead of "ve-".
Sets the SELinux security context to be used to label processes
in the container.
Sets the SELinux security context to be used to label files in
the virtual API file systems in the container.
List one or more additional capabilities to grant the container.
Takes a comma-separated list of capability names, see
capabilities(7) for more information. Note that the following
capabilities will be granted in any way: CAP_CHOWN,
CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH, CAP_FOWNER, CAP_FSETID,
CAP_IPC_OWNER, CAP_KILL, CAP_LEASE, CAP_LINUX_IMMUTABLE,
CAP_NET_BIND_SERVICE, CAP_NET_BROADCAST, CAP_NET_RAW, CAP_SETGID,
CAP_SETFCAP, CAP_SETPCAP, CAP_SETUID, CAP_SYS_ADMIN,
CAP_SYS_CHROOT, CAP_SYS_NICE, CAP_SYS_PTRACE, CAP_SYS_TTY_CONFIG,
CAP_SYS_RESOURCE, CAP_SYS_BOOT, CAP_AUDIT_WRITE,
CAP_AUDIT_CONTROL. Also CAP_NET_ADMIN is retained if
--private-network is specified. If the special value "all" is
passed, all capabilities are retained.
Specify one or more additional capabilities to drop for the
container. This allows running the container with fewer
capabilities than the default (see above).
Control whether the container's journal shall be made visible to
the host system. If enabled, allows viewing the container's
journal files from the host (but not vice versa). Takes one of
"no", "host", "guest", "auto". If "no", the journal is not
linked. If "host", the journal files are stored on the host file
system (beneath /var/log/journal/machine-id) and the subdirectory
is bind-mounted into the container at the same location. If
"guest", the journal files are stored on the guest file system
(beneath /var/log/journal/machine-id) and the subdirectory is
symlinked into the host at the same location. If "auto" (the
default), and the right subdirectory of /var/log/journal exists,
it will be bind mounted into the container. If the subdirectory
does not exist, no linking is performed. Effectively, booting a
container once with "guest" or "host" will link the journal
persistently if further on the default of "auto" is used.
Equivalent to --link-journal=guest.
Mount the root file system read-only for the container.
Bind mount a file or directory from the host into the container.
Either takes a path argument -- in which case the specified path
will be mounted from the host to the same path in the container
--, 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 container. The --bind-ro= option creates
read-only bind mounts.
Mount a tmpfs file system into the container. Takes a single
absolute path argument that specifies where to mount the tmpfs
instance to (in which case the directory access mode will be
chosen as 0755, owned by root/root), or optionally a
colon-separated pair of path and mount option string, that is
used for mounting (in which case the kernel default for access
mode and owner will be chosen, unless otherwise specified). This
option is particularly useful for mounting directories such as
/var as tmpfs, to allow state-less systems, in particular when
combined with --read-only.
Specifies an environment variable assignment to pass to the init
process in the container, in the format "NAME=VALUE". This may be
used to override the default variables or to set additional
variables. This parameter may be used more than once.
Allows the container to share certain system facilities with the
host. More specifically, this turns off PID namespacing, UTS
namespacing and IPC namespacing, and thus allows the guest to see
and interact more easily with processes outside of the container.
Note that using this option makes it impossible to start up a
full Operating System in the container, as an init system cannot
operate in this mode. It is only useful to run specific programs
or applications this way, without involving an init system in the
container. This option implies --register=no. This option may not
be combined with --boot.
Controls whether the container is registered with
systemd-machined(8). Takes a boolean argument, defaults to "yes".
This option should be enabled when the container runs a full
Operating System (more specifically: an init system), and is
useful to ensure that the container is accessible via
machinectl(1) and shown by tools such as ps(1). If the container
does not run an init system, it is recommended to set this option
to "no". Note that --share-system implies --register=no.
Instead of creating a transient scope unit to run the container
in, simply register the service or scope unit systemd-nspawn has
been invoked in with systemd-machined(8). This has no effect if
--register=no is used. This switch should be used if
systemd-nspawn is invoked from within a service unit, and the
service unit's sole purpose is to run a single systemd-nspawn
container. This option is not available if run from a user
Control the architecture ("personality") reported by uname(2) in
the container. Currently, only "x86" and "x86-64" are supported.
This is useful when running a 32-bit container on a 64-bit host.
If this setting is not used, the personality reported in the
container is the same as the one reported on the host.
Turns off any status output by the tool itself. When this switch
is used, the only output from nspawn will be the console output
of the container OS itself.
Boots the container in volatile (ephemeral) mode. When no mode
parameter is passed or when mode is specified as "yes" full
volatile mode is enabled. This means the root directory is
mounted as mostly unpopulated "tmpfs" instance, and /usr from the
OS tree is mounted into it, read-only (the system thus starts up
with read-only OS resources, but pristine state and
configuration, any changes to the either are lost on shutdown).
When the mode parameter is specified as "state" the OS tree is
mounted read-only, but /var is mounted as "tmpfs" instance into
it (the system thus starts up with read-only OS resources and
configuration, but pristine state, any changes to the latter are
lost on shutdown). When the mode parameter is specified as "no"
(the default) the whole OS tree is made available writable.
Note that setting this to "yes" or "state" will only work
correctly with operating systems in the container that can boot
up with only /usr mounted, and are able to populate /var
automatically, as needed.
Print a short help text and exit.
Print a short version string and exit.
# yum -y --releasever=19 --nogpg --installroot=/srv/mycontainer --disablerepo='*' --enablerepo=fedora install systemd passwd yum fedora-release vim-minimal
# systemd-nspawn -bD /srv/mycontainer
This installs a minimal Fedora distribution into the directory
/srv/mycontainer/ and then boots an OS in a namespace container in
# debootstrap --arch=amd64 unstable ~/debian-tree/
# systemd-nspawn -D ~/debian-tree/
This installs a minimal Debian unstable distribution into the
directory ~/debian-tree/ and then spawns a shell in a namespace
container in it.
# pacstrap -c -d ~/arch-tree/ base
# systemd-nspawn -bD ~/arch-tree/
This installs a mimimal Arch Linux distribution into the directory
~/arch-tree/ and then boots an OS in a namespace container in it.
# mv ~/arch-tree /var/lib/container/arch
# systemctl enable email@example.com
# systemctl start firstname.lastname@example.org
This makes the Arch Linux container part of the multi-user.target on
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
page was obtained from the project's upstream Git repository
(git://anongit.freedesktop.org/systemd/systemd) on 2014-10-02. 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 email@example.com
systemd 216 SYSTEMD-NSPAWN(1)