SYSTEMD-NSPAWN(1)systemd-nspawnSYSTEMD-NSPAWN(1)NAMEsystemd-nspawn - Spawn a namespace container for debugging, testing and
building
SYNOPSISsystemd-nspawn [OPTIONS...] [COMMAND [ARGS...]]
systemd-nspawn-b [OPTIONS...] [ARGS...]
DESCRIPTIONsystemd-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
/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 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", "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.
-j
Equivalent to --link-journal=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.
--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 32bit container on a 64bit 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@arch.service
# systemctl start systemd-nspawn@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 ALSOsystemd(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 212SYSTEMD-NSPAWN(1)
