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= is specified
the directory is determined as /var/lib/machines/ suffixed by the machine
name as specified with --machine=. If neither --directory=,
--image=, nor --machine= are specified, the current directory
will be used. May not be specified together with --image=.
--template=
Directory or "btrfs" subvolume to use as
template for the container's root directory. If this is specified and the
container's root directory (as configured by --directory=) does not yet
exist it is created as "btrfs" subvolume and populated from this
template tree. Ideally, the specified template path refers to the root of a
"btrfs" subvolume, in which case a simple copy-on-write snapshot is
taken, and populating the root directory is instant. If the specified template
path does not refer to the root of a "btrfs" subvolume (or not even
to a "btrfs" file system at all), the tree is copied, which can be
substantially more time-consuming. Note that if this option is used the
container's root directory (in contrast to the template directory!) must be
located on a "btrfs" file system, so that the "btrfs"
subvolume may be created. May not be specified together with --image=
or --ephemeral.
-x, --ephemeral
If specified, the container is run with a temporary
"btrfs" snapshot of its root directory (as configured with
--directory=), that is removed immediately when the container
terminates. This option is only supported if the root file system is
"btrfs". May not be specified together with --image= or
--template=.
-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 either:
•An MBR partition table with a single partition of
type 0x83 that is marked bootable.
•A GUID partition table (GPT) with a single
partition of type 0fc63daf-8483-4772-8e79-3d69d8477de4.
•A GUID partition table (GPT) with a marked root
partition which is mounted as the root directory of the container. Optionally,
GPT images 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=, --template= or --ephemeral.
-a, --as-pid2
Invoke the shell or specified program as process ID (PID)
2 instead of PID 1 (init). By default, if neither this option nor
--boot is used, the selected binary is run as process with PID 1, a
mode only suitable for programs that are aware of the special semantics that
the process with PID 1 has on UNIX. For example, it needs to reap all
processes reparented to it, and should implement sysvinit compatible
signal handling (specifically: it needs to reboot on SIGINT, reexecute on
SIGTERM, reload configuration on SIGHUP, and so on). With --as-pid2 a
minimal stub init process is run as PID 1 and the selected binary is executed
as PID 2 (and hence does not need to implement any special semantics). The
stub init process will reap processes as necessary and react appropriately to
signals. It is recommended to use this mode to invoke arbitrary commands in
containers, unless they have been modified to run correctly as PID 1. Or in
other words: this switch should be used for pretty much all commands, except
when the command refers to an init or shell implementation, as these are
generally capable of running correctly as PID 1). This option may not be
combined with --boot or --share-system.
-b, --boot
Automatically search for an init binary and invoke it as
PID 1, 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
--as-pid2 or
--share-system.
The following table explains the different modes of invocation and
relationship to --as-pid2 (see above):
Table 1. Invocation Mode
| Switch |
Explanation |
| Neither --as-pid2 nor --boot specified |
The passed parameters are interpreted as command line, which is executed
as PID 1 in the container. |
| --as-pid2 specified |
The passed parameters are interpreted as command line, which are
executed as PID 2 in the container. A stub init process is run as PID
1. |
| --boot specified |
An init binary as automatically searched and run as PID 1 in the
container. The passed parameters are used as invocation parameters for
this process. |
-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 during its runtime (for example in tools
like
machinectl(1) and similar), 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 path of the container
is used, possibly suffixed with a random identifier in case
--ephemeral
mode is selected. If the root directory selected is the host's root directory
the host's hostname is used as default instead.
--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-ipvlan=
Create an "ipvlan" interface of the specified
Ethernet network interface and add it to the container. An "ipvlan"
interface is a virtual interface, similar to a "macvlan" interface,
which uses the same MAC address as the underlying interface. The interface in
the container will be named after the interface on the host, prefixed with
"iv-". Note that --network-ipvlan= implies
--private-network. This option may be used more than once to add
multiple network interfaces to the container.
-n, --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-".
-p, --port=
If private networking is enabled, maps an IP port on the
host onto an IP port on the container. Takes a protocol specifier (either
"tcp" or "udp"), separated by a colon from a host port
number in the range 1 to 65535, separated by a colon from a container port
number in the range from 1 to 65535. The protocol specifier and its separating
colon may be omitted, in which case "tcp" is assumed. The container
port number and its colon may be ommitted, in which case the same port as the
host port is implied. This option is only supported if private networking is
used, such as --network-veth or --network-bridge=.
-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 persistent 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.
--volatile=MODE
Boots the container in volatile 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.
--version
Print a short version string and exit.