SYSTEMD-NSPAWN(1)              systemd-nspawn              SYSTEMD-NSPAWN(1)

NAME         top

       systemd-nspawn - Spawn a namespace container for debugging, testing
       and building

SYNOPSIS         top

       systemd-nspawn [OPTIONS...] [COMMAND [ARGS...]]

       systemd-nspawn -b [OPTIONS...] [ARGS...]

DESCRIPTION         top

       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
       container exits.

       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[1] 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.

OPTIONS         top

       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:

       -D, --directory=
           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

       -i, --image=
           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 Partitions
           Specification[2]. Any other partitions, such as foreign
           partitions, swap partitions or EFI system partitions are not
           mounted. May not be specified together with --directory=.

       -b, --boot
           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

       -u, --user=
           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

       -M, --machine=
           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
           default machine.slice.

           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
           the container.

           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-".

       -Z, --selinux-context=
           Sets the SELinux security context to be used to label processes
           in the container.

       -L, --selinux-apifs-context=
           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_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=, --bind-ro=
           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.

       -q, --quiet
           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.

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

           Print a short version string and exit.

EXAMPLE 1         top

           # 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

EXAMPLE 2         top

           # 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.

EXAMPLE 3         top

           # 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.

EXAMPLE 4         top

           # mv ~/arch-tree /var/lib/container/arch
           # systemctl enable systemd-nspawn@arch.service
           # systemctl start systemd-nspawn@arch.service

       This makes the Arch Linux container part of the on
       the host.

EXAMPLE 5         top

           # btrfs subvolume snapshot / /.tmp
           # systemd-nspawn --private-network -D /.tmp -b

       This runs a copy of the host system in a btrfs snapshot.

EXAMPLE 6         top

           # chcon system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -R /srv/container
           # systemd-nspawn -L system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -Z system_u:system_r:svirt_lxc_net_t:s0:c0,c1 -D /srv/container /bin/sh

       This runs a container with SELinux sandbox security contexts.

EXIT STATUS         top

       The exit code of the program executed in the container is returned.

SEE ALSO         top

       systemd(1), chroot(1), yum(8), debootstrap(8), pacman(8),
       systemd.slice(5), machinectl(1)

NOTES         top

        1. Container Interface

        2. Discoverable Partitions Specification

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
       (git:// 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
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       mail to

systemd 216                                                SYSTEMD-NSPAWN(1)