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



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

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

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

DESCRIPTION
       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 containers.

       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
       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 --image=.

       -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
           --share-system.

       -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
           only.

       -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.

       --uuid=
           Set the specified UUID for the container. The init system will initialize
           /etc/machine-id from this if this file is not set yet.

       --slice=
           Make the container part of the specified slice, instead of the default machine.slice.

       --private-network
           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=.

       --network-interface=
           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 container.

       --network-macvlan=
           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.

       --network-veth
           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.

       --network-bridge=
           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.

       --capability=
           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.

       --drop-capability=
           Specify one or more additional capabilities to drop for the container. This allows
           running the container with fewer capabilities than the default (see above).

       --link-journal=
           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", "try-host", "guest", "try-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.  "try-host" and "try-guest" do the same
           but do not fail if the host does not have persistant journalling enabled. 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.

       -j
           Equivalent to --link-journal=try-guest.

       --read-only
           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.

       --tmpfs=
           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.

       --setenv=
           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.

       --share-system
           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.

       --register=
           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.

       --keep-unit
           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 session.

       --personality=
           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.

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

       --version
           Print a short version string and exit.

EXAMPLE 1
           # 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 it.

EXAMPLE 2
           # 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
           # 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
           # mv ~/arch-tree /var/lib/container/arch
           # systemctl enable systemd-nspawn AT arch.service
           # systemctl start systemd-nspawn AT arch.service

       This makes the Arch Linux container part of the multi-user.target on the host.

EXAMPLE 5
           # 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
           # 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
       The exit code of the program executed in the container is returned.

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

NOTES
        1. Container Interface
           http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface

        2. Discoverable Partitions Specification
           http://www.freedesktop.org/wiki/Specifications/DiscoverablePartitionsSpec/



systemd 215                                                                     SYSTEMD-NSPAWN(1)