OPTIONS¶
If option -b is specified, the arguments are used as
arguments for the init program. Otherwise, COMMAND specifies the
program to launch in the container, and the remaining arguments are used as
arguments for this program. If --boot is not used and no arguments
are specified, 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 by searching for a directory named the same as
the machine name specified with --machine=. See machinectl(1)
section "Files and Directories" for the precise search path.
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" snapshot (if supported) or plain
directory (otherwise) 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 (though possibly in a copy-on-write
scheme — if the file system supports that), which can be substantially
more time-consuming. May not be specified together with
--image= or
--ephemeral.
Note that this switch leaves host name, machine ID and all other
settings that could identify the instance unmodified.
-x, --ephemeral
If specified, the container is run with a temporary
snapshot of its file system that is removed immediately when the container
terminates. May not be specified together with
--template=.
Note that this switch leaves host name, machine ID and all other
settings that could identify the instance unmodified.
-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].
•No partition table, and a single file system
spanning the whole image.
On GPT images, if an EFI System Partition (ESP) is discovered, it
is automatically mounted to /efi (or /boot as fallback) in case a directory
by this name exists and is empty.
Partitions encrypted with LUKS are automatically decrypted. Also,
on GPT images dm-verity data integrity hash partitions are set up if the
root hash for them is specified using the --root-hash= option.
Any other partitions, such as foreign partitions or swap
partitions are not mounted. May not be specified together with
--directory=, --template=.
--root-hash=
Takes a data integrity (dm-verity) root hash specified in
hexadecimal. This option enables data integrity checks using dm-verity, if the
used image contains the appropriate integrity data (see above). The specified
hash must match the root hash of integrity data, and is usually at least 256
bits (and hence 64 formatted hexadecimal characters) long (in case of SHA256
for example). If this option is not specified, but the image file carries the
"user.verity.roothash" extended file attribute (see
xattr(7)), then the root hash is read from it, also as formatted
hexadecimal characters. If the extended file attribute is not found (or is not
supported by the underlying file system), but a file with the .roothash suffix
is found next to the image file, bearing otherwise the same name, the root
hash is read from it and automatically used, also as formatted hexadecimal
characters.
-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 program is run as the 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 program 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.
-b, --boot
Automatically search for an init program 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
program. This option may not be combined with
--as-pid2.
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 the command line, which is
executed as PID 1 in the container. |
| --as-pid2 specified |
The passed parameters are interpreted as the command line, which is
executed as PID 2 in the container. A stub init process is run as PID
1. |
| --boot specified |
An init program is automatically searched for and run as PID 1 in the
container. The passed parameters are used as invocation parameters for
this process. |
Note that
--boot is the default mode of operation if the systemd-nspawn@.service
template unit file is used.
--chdir=
Change to the specified working directory before invoking
the process in the container. Expects an absolute path in the container's file
system namespace.
--pivot-root=
Pivot the specified directory to / inside the container,
and either unmount the container's old root, or pivot it to another specified
directory. Takes one of: a path argument — in which case the specified
path will be pivoted to / and the old root will be unmounted; or a
colon-separated pair of new root path and pivot destination for the old root.
The new root path will be pivoted to /, and the old / will be pivoted to the
other directory. Both paths must be absolute, and are resolved in the
container's file system namespace.
This is for containers which have several bootable directories in
them; for example, several OSTree[3] deployments. It emulates the
behavior of the boot loader and initial RAM disk which normally select which
directory to mount as the root and start the container's PID 1 in.
-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.
--hostname=
Controls the hostname to set within the container, if
different from the machine name. Expects a valid hostname as argument. If this
option is used, the kernel hostname of the container will be set to this
value, otherwise it will be initialized to the machine name as controlled by
the --machine= option described above. The machine name is used for
various aspect of identification of the container from the outside, the kernel
hostname configurable with this option is useful for the container to identify
itself from the inside. It is usually a good idea to keep both forms of
identification synchronized, in order to avoid confusion. It is hence
recommended to avoid usage of this option, and use --machine=
exclusively. Note that regardless whether the container's hostname is
initialized from the name set with --hostname= or the one set with
--machine=, the container can later override its kernel hostname freely
on its own as well.
--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. Note
that this option takes effect only if /etc/machine-id in the container is
unpopulated.
-S, --slice=
Make the container part of the specified slice, instead
of the default machine.slice. This applies only if the machine is run in its
own scope unit, i.e. if --keep-unit isn't used.
--property=
Set a unit property on the scope unit to register for the
machine. This applies only if the machine is run in its own scope unit, i.e.
if --keep-unit isn't used. Takes unit property assignments in the same
format as systemctl set-property. This is useful to set memory limits
and similar for container.
--private-users=
Controls user namespacing. If enabled, the container will
run with its own private set of UNIX user and group ids (UIDs and GIDs). This
involves mapping the private UIDs/GIDs used in the container (starting with
the container's root user 0 and up) to a range of UIDs/GIDs on the host that
are not used for other purposes (usually in the range beyond the host's
UID/GID 65536). The parameter may be specified as follows:
1.If one or two colon-separated numbers are specified,
user namespacing is turned on. The first parameter specifies the first host
UID/GID to assign to the container, the second parameter specifies the number
of host UIDs/GIDs to assign to the container. If the second parameter is
omitted, 65536 UIDs/GIDs are assigned.
2.If the parameter is omitted, or true, user namespacing
is turned on. The UID/GID range to use is determined automatically from the
file ownership of the root directory of the container's directory tree. To use
this option, make sure to prepare the directory tree in advance, and ensure
that all files and directories in it are owned by UIDs/GIDs in the range you'd
like to use. Also, make sure that used file ACLs exclusively reference
UIDs/GIDs in the appropriate range. If this mode is used the number of
UIDs/GIDs assigned to the container for use is 65536, and the UID/GID of the
root directory must be a multiple of 65536.
3.If the parameter is false, user namespacing is turned
off. This is the default.
4.The special value "pick" turns on user
namespacing. In this case the UID/GID range is automatically chosen. As first
step, the file owner of the root directory of the container's directory tree
is read, and it is checked that it is currently not used by the system
otherwise (in particular, that no other container is using it). If this check
is successful, the UID/GID range determined this way is used, similar to the
behavior if "yes" is specified. If the check is not successful (and
thus the UID/GID range indicated in the root directory's file owner is already
used elsewhere) a new – currently unused – UID/GID range of
65536 UIDs/GIDs is randomly chosen between the host UID/GIDs of 524288 and
1878982656, always starting at a multiple of 65536. This setting implies
--private-users-chown (see below), which has the effect that the files
and directories in the container's directory tree will be owned by the
appropriate users of the range picked. Using this option makes user namespace
behavior fully automatic. Note that the first invocation of a previously
unused container image might result in picking a new UID/GID range for it, and
thus in the (possibly expensive) file ownership adjustment operation. However,
subsequent invocations of the container will be cheap (unless of course the
picked UID/GID range is assigned to a different use by then).
It is recommended to assign at least 65536 UIDs/GIDs to each
container, so that the usable UID/GID range in the container covers 16 bit.
For best security, do not assign overlapping UID/GID ranges to multiple
containers. It is hence a good idea to use the upper 16 bit of the host
32-bit UIDs/GIDs as container identifier, while the lower 16 bit encode the
container UID/GID used. This is in fact the behavior enforced by the
--private-users=pick option.
When user namespaces are used, the GID range assigned to each
container is always chosen identical to the UID range.
In most cases, using --private-users=pick is the
recommended option as it enhances container security massively and operates
fully automatically in most cases.
Note that the picked UID/GID range is not written to /etc/passwd
or /etc/group. In fact, the allocation of the range is not stored
persistently anywhere, except in the file ownership of the files and
directories of the container.
Note that when user namespacing is used file ownership on disk
reflects this, and all of the container's files and directories are owned by
the container's effective user and group IDs. This means that copying files
from and to the container image requires correction of the numeric UID/GID
values, according to the UID/GID shift applied.
--private-users-chown
If specified, all files and directories in the
container's directory tree will adjusted so that they are owned to the
appropriate UIDs/GIDs selected for the container (see above). This operation
is potentially expensive, as it involves descending and iterating through the
full directory tree of the container. Besides actual file ownership, file ACLs
are adjusted as well.
This option is implied if --private-users=pick is used.
This option has no effect if user namespacing is not used.
-U
If the kernel supports the user namespaces feature,
equivalent to
--private-users=pick --private-users-chown, otherwise
equivalent to
--private-users=no.
Note that -U is the default if the systemd-nspawn@.service
template unit file is used.
Note: it is possible to undo the effect of
--private-users-chown (or -U) on the file system by redoing
the operation with the first UID of 0:
systemd-nspawn ... --private-users=0 --private-users-chown
--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=. If this option is not specified (or implied by one
of the options listed below), the container will have full access to the host
network.
--network-namespace-path=
Takes the path to a file representing a kernel network
namespace that the container shall run in. The specified path should refer to
a (possibly bind-mounted) network namespace file, as exposed by the kernel
below /proc/$PID/ns/net. This makes the container enter the given network
namespace. One of the typical use cases is to give a network namespace under
/run/netns created by
ip-netns(8), for example,
--network-namespace-path=/run/netns/foo. Note that this option cannot
be used together with other network-related options, such as
--private-network or
--network-interface=.
--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". The
--network-veth
option implies
--private-network.
Note that systemd-networkd.service(8) includes by default a
network file /usr/lib/systemd/network/80-container-ve.network matching the
host-side interfaces created this way, which contains settings to enable
automatic address provisioning on the created virtual link via DHCP, as well
as automatic IP routing onto the host's external network interfaces. It also
contains /usr/lib/systemd/network/80-container-host0.network matching the
container-side interface created this way, containing settings to enable
client side address assignment via DHCP. In case systemd-networkd is running
on both the host and inside the container, automatic IP communication from
the container to the host is thus available, with further connectivity to
the external network.
Note that --network-veth is the default if the
systemd-nspawn@.service template unit file is used.
--network-veth-extra=
Adds an additional virtual Ethernet link between host and
container. Takes a colon-separated pair of host interface name and container
interface name. The latter may be omitted in which case the container and host
sides will be assigned the same name. This switch is independent of
--network-veth, and — in contrast — may be used multiple
times, and allows configuration of the network interface names. Note that
--network-bridge= has no effect on interfaces created with
--network-veth-extra=.
--network-bridge=
Adds the host side of the Ethernet link created with
--network-veth to the specified Ethernet bridge interface. Expects a
valid network interface name of a bridge device as argument. 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-".
--network-zone=
Creates a virtual Ethernet link ("veth") to the
container and adds it to an automatically managed Ethernet bridge interface.
The bridge interface is named after the passed argument, prefixed with
"vz-". The bridge interface is automatically created when the first
container configured for its name is started, and is automatically removed
when the last container configured for its name exits. Hence, each bridge
interface configured this way exists only as long as there's at least one
container referencing it running. This option is very similar to
--network-bridge=, besides this automatic creation/removal of the
bridge device.
This setting makes it easy to place multiple related containers on
a common, virtual Ethernet-based broadcast domain, here called a
"zone". Each container may only be part of one zone, but each zone
may contain any number of containers. Each zone is referenced by its name.
Names may be chosen freely (as long as they form valid network interface
names when prefixed with "vz-"), and it is sufficient to pass the
same name to the --network-zone= switch of the various concurrently
running containers to join them in one zone.
Note that systemd-networkd.service(8) includes by default a
network file /usr/lib/systemd/network/80-container-vz.network matching the
bridge interfaces created this way, which contains settings to enable
automatic address provisioning on the created virtual network via DHCP, as
well as automatic IP routing onto the host's external network interfaces.
Using --network-zone= is hence in most cases fully automatic and
sufficient to connect multiple local containers in a joined broadcast domain
to the host, with further connectivity to the external network.
-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 omitted, in which case the same port as the
host port is implied. This option is only supported if private networking is
used, such as with --network-veth, --network-zone=
--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_AUDIT_CONTROL, CAP_AUDIT_WRITE,
CAP_CHOWN, CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH, CAP_FOWNER, CAP_FSETID,
CAP_IPC_OWNER, CAP_KILL, CAP_LEASE, CAP_LINUX_IMMUTABLE, CAP_MKNOD,
CAP_NET_BIND_SERVICE, CAP_NET_BROADCAST, CAP_NET_RAW, CAP_SETFCAP, CAP_SETGID,
CAP_SETPCAP, CAP_SETUID, CAP_SYS_ADMIN, CAP_SYS_BOOT, CAP_SYS_CHROOT,
CAP_SYS_NICE, CAP_SYS_PTRACE, CAP_SYS_RESOURCE, CAP_SYS_TTY_CONFIG. 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).
--no-new-privileges=
Takes a boolean argument. Specifies the value of the
PR_SET_NO_NEW_PRIVS flag for the container payload. Defaults to off.
When turned on the payload code of the container cannot acquire new
privileges, i.e. the "setuid" file bit as well as file system
capabilities will not have an effect anymore. See
prctl(2) for details
about this flag.
--system-call-filter=
Alter the system call filter applied to containers. Takes
a space-separated list of system call names or group names (the latter
prefixed with "@", as listed by the
syscall-filter command of
systemd-analyze(1)). Passed system calls will be permitted. The list
may optionally be prefixed by "~", in which case all listed system
calls are prohibited. If this command line option is used multiple times the
configured lists are combined. If both a positive and a negative list (that is
one system call list without and one with the "~" prefix) are
configured, the negative list takes precedence over the positive list. Note
that
systemd-nspawn always implements a system call whitelist (as
opposed to a blacklist), and this command line option hence adds or removes
entries from the default whitelist, depending on the "~" prefix.
Note that the applied system call filter is also altered implicitly if
additional capabilities are passed using the
--capabilities=.
--rlimit=
Sets the specified POSIX resource limit for the container
payload. Expects an assignment of the form
"
LIMIT=
SOFT:
HARD" or
"
LIMIT=
VALUE", where
LIMIT should refer to a
resource limit type, such as
RLIMIT_NOFILE or
RLIMIT_NICE. The
SOFT and
HARD fields should refer to the numeric soft and hard
resource limit values. If the second form is used,
VALUE may specify a
value that is used both as soft and hard limit. In place of a numeric value
the special string "infinity" may be used to turn off resource
limiting for the specific type of resource. This command line option may be
used multiple times to control limits on multiple limit types. If used
multiple times for the same limit type, the last use wins. For details about
resource limits see
setrlimit(2). By default resource limits for the
container's init process (PID 1) are set to the same values the Linux kernel
originally passed to the host init system. Note that some resource limits are
enforced on resources counted per user, in particular
RLIMIT_NPROC.
This means that unless user namespacing is deployed (i.e.
--private-users= is used, see above), any limits set will be applied to
the resource usage of the same user on all local containers as well as the
host. This means particular care needs to be taken with these limits as they
might be triggered by possibly less trusted code. Example:
"--rlimit=RLIMIT_NOFILE=8192:16384".
--oom-score-adjust=
Changes the OOM ("Out Of Memory") score
adjustment value for the container payload. This controls
/proc/self/oom_score_adj which influences the preference with which this
container is terminated when memory becomes scarce. For details see
proc(5). Takes an integer in the range -1000...1000.
--cpu-affinity=
Controls the CPU affinity of the container payload. Takes
a comma separated list of CPU numbers or number ranges (the latter's start and
end value separated by dashes). See
sched_setaffinity(2) for
details.
--kill-signal=
Specify the process signal to send to the container's PID
1 when nspawn itself receives
SIGTERM, in order to trigger an orderly
shutdown of the container. Defaults to
SIGRTMIN+3 if
--boot is
used (on systemd-compatible init systems
SIGRTMIN+3 triggers an orderly
shutdown). If
--boot is not used and this option is not specified the
container's processes are terminated abrubtly via
SIGKILL. For a list
of valid signals, see
signal(7).
--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 journaling
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.
Note that --link-journal=try-guest is the default if the
systemd-nspawn@.service template unit file is used.
-j
Equivalent to --link-journal=try-guest.
--resolv-conf=
Configures how /etc/resolv.conf inside of the container
(i.e. DNS configuration synchronization from host to container) shall be
handled. Takes one of "off", "copy-host",
"copy-static", "bind-host", "bind-static",
"delete" or "auto". If set to "off" the
/etc/resolv.conf file in the container is left as it is included in the image,
and neither modified nor bind mounted over. If set to "copy-host",
the /etc/resolv.conf file from the host is copied into the container. Similar,
if "bind-host" is used, the file is bind mounted from the host into
the container. If set to "copy-static" the static resolv.conf file
supplied with
systemd-resolved.service(8) is copied into the container,
and correspondingly "bind-static" bind mounts it there. If set to
"delete" the /etc/resolv.conf file in the container is deleted if it
exists. Finally, if set to "auto" the file is left as it is if
private networking is turned on (see
--private-network). Otherwise, if
systemd-resolved.service is connectible its static resolv.conf file is used,
and if not the host's /etc/resolv.conf file is used. In the latter cases the
file is copied if the image is writable, and bind mounted otherwise. It's
recommended to use "copy" if the container shall be able to make
changes to the DNS configuration on its own, deviating from the host's
settings. Otherwise "bind" is preferable, as it means direct changes
to /etc/resolv.conf in the container are not allowed, as it is a read-only
bind mount (but note that if the container has enough privileges, it might
simply go ahead and unmount the bind mount anyway). Note that both if the file
is bind mounted and if it is copied no further propagation of configuration is
generally done after the one-time early initialization (this is because the
file is usually updated through copying and renaming). Defaults to
"auto".
--timezone=
Configures how /etc/localtime inside of the container
(i.e. local timezone synchronization from host to container) shall be handled.
Takes one of "off", "copy", "bind",
"symlink", "delete" or "auto". If set to
"off" the /etc/localtime file in the container is left as it is
included in the image, and neither modified nor bind mounted over. If set to
"copy" the /etc/localtime file of the host is copied into the
container. Similar, if "bind" is used, it is bind mounted from the
host into the container. If set to "symlink" a symlink from
/etc/localtime in the container is created pointing to the matching the
timezone file of the container that matches the timezone setting on the host.
If set to "delete" the file in the container is deleted, should it
exist. If set to "auto" and the /etc/localtime file of the host is a
symlink, then "symlink" mode is used, and "copy"
otherwise, except if the image is read-only in which case "bind" is
used instead. Defaults to "auto".
--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. Takes one of: 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, or a colon-separated triple of source path,
destination path and mount options. The source path may optionally be prefixed
with a "+" character. If so, the source path is taken relative to
the image's root directory. This permits setting up bind mounts within the
container image. The source path may be specified as empty string, in which
case a temporary directory below the host's /var/tmp directory is used. It is
automatically removed when the container is shut down. Mount options are
comma-separated and currently, only
rbind and
norbind are
allowed, controlling whether to create a recursive or a regular bind mount.
Defaults to "rbind". Backslash escapes are interpreted, so
"\:" may be used to embed colons in either path. This option may be
specified multiple times for creating multiple independent bind mount points.
The
--bind-ro= option creates read-only bind mounts.
Note that when this option is used in combination with
--private-users, the resulting mount points will be owned by the
nobody user. That's because the mount and its files and directories
continue to be owned by the relevant host users and groups, which do not
exist in the container, and thus show up under the wildcard UID 65534
(nobody). If such bind mounts are created, it is recommended to make them
read-only, using --bind-ro=.
--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.
Backslash escapes are interpreted in the path, so "\:" may be used
to embed colons in the path.
--overlay=, --overlay-ro=
Combine multiple directory trees into one overlay file
system and mount it into the container. Takes a list of colon-separated paths
to the directory trees to combine and the destination mount point.
Backslash escapes are interpreted in the paths, so "\:"
may be used to embed colons in the paths.
If three or more paths are specified, then the last specified path
is the destination mount point in the container, all paths specified before
refer to directory trees on the host and are combined in the specified order
into one overlay file system. The left-most path is hence the lowest
directory tree, the second-to-last path the highest directory tree in the
stacking order. If --overlay-ro= is used instead of
--overlay=, a read-only overlay file system is created. If a writable
overlay file system is created, all changes made to it are written to the
highest directory tree in the stacking order, i.e. the second-to-last
specified.
If only two paths are specified, then the second specified path is
used both as the top-level directory tree in the stacking order as seen from
the host, as well as the mount point for the overlay file system in the
container. At least two paths have to be specified.
The source paths may optionally be prefixed with "+"
character. If so they are taken relative to the image's root directory. The
uppermost source path may also be specified as empty string, in which case a
temporary directory below the host's /var/tmp is used. The directory is
removed automatically when the container is shut down. This behaviour is
useful in order to make read-only container directories writable while the
container is running. For example, use the "--overlay=+/var::/var"
option in order to automatically overlay a writable temporary directory on a
read-only /var directory.
For details about overlay file systems, see
overlayfs.txt[4]. Note that the semantics of overlay file systems are
substantially different from normal file systems, in particular regarding
reported device and inode information. Device and inode information may
change for a file while it is being written to, and processes might see
out-of-date versions of files at times. Note that this switch automatically
derives the "workdir=" mount option for the overlay file system
from the top-level directory tree, making it a sibling of it. It is hence
essential that the top-level directory tree is not a mount point itself
(since the working directory must be on the same file system as the top-most
directory tree). Also note that the "lowerdir=" mount option
receives the paths to stack in the opposite order of this switch.
-E NAME=VALUE,
--setenv=NAME=VALUE
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.
--register=
Controls whether the container is registered with
systemd-machined(8). Takes a boolean argument, which defaults to
"yes". This option should be enabled when the container runs a full
Operating System (more specifically: a system and service manager as PID 1),
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 a service manager, it is recommended to set this option to
"no".
--keep-unit
Instead of creating a transient scope unit to run the
container in, simply use the service or scope unit
systemd-nspawn has
been invoked in. If
--register=yes is set this unit is registered with
systemd-machined(8). 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.
Note that passing --keep-unit disables the effect of
--slice= and --property=. Use --keep-unit and
--register=no in combination to disable any kind of unit allocation
or registration with systemd-machined.
--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, --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 a mostly
unpopulated "tmpfs" instance, and /usr from the OS tree is mounted
into it in read-only mode (the system thus starts up with read-only OS image,
but pristine state and configuration, any changes are lost on shutdown). When
the mode parameter is specified as
state, the OS tree is mounted
read-only, but /var is mounted as a "tmpfs" instance into it (the
system thus starts up with read-only OS resources and configuration, but
pristine state, and 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.
This option provides similar functionality for containers as the
"systemd.volatile=" kernel command line switch provides for host
systems. See kernel-command-line(7) for details.
Note that enabling this setting will only work correctly with
operating systems in the container that can boot up with only /usr mounted,
and are able to automatically populate /var, and also /etc in case of
"--volatile=yes".
--settings=MODE
Controls whether
systemd-nspawn shall search for
and use additional per-container settings from .nspawn files. Takes a boolean
or the special values
override or
trusted.
If enabled (the default), a settings file named after the machine
(as specified with the --machine= setting, or derived from the
directory or image file name) with the suffix .nspawn is searched in
/etc/systemd/nspawn/ and /run/systemd/nspawn/. If it is found there, its
settings are read and used. If it is not found there, it is subsequently
searched in the same directory as the image file or in the immediate parent
of the root directory of the container. In this case, if the file is found,
its settings will be also read and used, but potentially unsafe settings are
ignored. Note that in both these cases, settings on the command line take
precedence over the corresponding settings from loaded .nspawn files, if
both are specified. Unsafe settings are considered all settings that elevate
the container's privileges or grant access to additional resources such as
files or directories of the host. For details about the format and contents
of .nspawn files, consult systemd.nspawn(5).
If this option is set to override, the file is searched,
read and used the same way, however, the order of precedence is reversed:
settings read from the .nspawn file will take precedence over the
corresponding command line options, if both are specified.
If this option is set to trusted, the file is searched,
read and used the same way, but regardless of being found in
/etc/systemd/nspawn/, /run/systemd/nspawn/ or next to the image file or
container root directory, all settings will take effect, however, command
line arguments still take precedence over corresponding settings.
If disabled, no .nspawn file is read and no settings except the
ones on the command line are in effect.
--notify-ready=
Configures support for notifications from the container's
init process.
--notify-ready= takes a boolean (
no and
yes). With option
no systemd-nspawn notifies systemd with a
"READY=1" message when the init process is created. With option
yes systemd-nspawn waits for the "READY=1" message from the
init process in the container before sending its own to systemd. For more
details about notifications see
sd_notify(3)).
-h, --help
Print a short help text and exit.
--version
Print a short version string and exit.