NAME
systemd-nspawn - Spawn a command or OS in a light-weight containerSYNOPSIS
systemd-nspawn
[OPTIONS...] [ COMMAND [ARGS...]]
systemd-nspawn
--boot [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 may be invoked on any directory tree containing an operating system tree, using the --directory= command line option. By using the --machine= option an OS tree is automatically searched for in a couple of locations, most importantly in /var/lib/machines/, the suggested directory to place OS container images installed on the system. In contrast to chroot(1) systemd-nspawn may be used to boot full Linux-based operating systems in a container. systemd-nspawn limits access to various kernel interfaces in the container to read-only, such as /sys/, /proc/sys/ or /sys/fs/selinux/. The host's 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. Use a tool like dnf(8), debootstrap(8), or pacman(8) to set up an OS directory tree suitable as file system hierarchy for systemd-nspawn containers. See the Examples section below for details on suitable invocation of these commands. As a safety check systemd-nspawn will verify the existence of /usr/lib/os-release or /etc/os-release in the container tree before booting a 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. systemd-nspawn may be invoked directly from the interactive command line or run as system service in the background. In this mode each container instance runs as its own service instance; a default template unit file [email protected] is provided to make this easy, taking the container name as instance identifier. Note that different default options apply when systemd-nspawn is invoked by the template unit file than interactively on the command line. Most importantly the template unit file makes use of the --boot option which is not the default in case systemd-nspawn is invoked from the interactive command line. Further differences with the defaults are documented along with the various supported options below. The machinectl(1) tool may be used to execute a number of operations on containers. In particular it provides easy-to-use commands to run containers as system services using the [email protected] template unit file. Along with each container a settings file with the .nspawn suffix may exist, containing additional settings to apply when running the container. See systemd.nspawn(5) for details. Settings files override the default options used by the [email protected] template unit file, making it usually unnecessary to alter this template file directly. 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. Rather use machinectl(1)'s login or shell commands to request an additional login session in a running container. systemd-nspawn implements the Container Interface[1] specification. While running, containers invoked with systemd-nspawn are registered with the systemd-machined(8) service that keeps track of running containers, and provides programming interfaces to interact with them.OPTIONS
If option --boot 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: -q, --quietTurns 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.
--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.
Image Options
-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 'reflink'
copy-on-write scheme — if the file system supports that), which can be
substantially more time-consuming. Note that the snapshot taken is of the
specified directory or subvolume, including all subdirectories and subvolumes
below it, but excluding any sub-mounts. May not be specified together with
--image= or --ephemeral.
Note that this switch leaves hostname, 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 hostname, machine ID and all other settings that
could identify the instance unmodified. Please note that — as with
--template= — taking the temporary snapshot is more efficient on
file systems that support subvolume snapshots or 'reflinks' natively
("btrfs" or new "xfs") than on more traditional file
systems that do not ("ext4"). Note that the snapshot taken is of the
specified directory or subvolume, including all subdirectories and subvolumes
below it, but excluding any sub-mounts.
With this option no modifications of the container image are retained. Use
--volatile= (described below) for other mechanisms to restrict
persistency of container images during runtime.
-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:
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.
Single file system images (i.e. file systems without a surrounding partition
table) can be opened using dm-verity if the integrity data is passed using the
--root-hash= and --verity-data= (and optionally
--root-hash-sig=) options.
Any other partitions, such as foreign partitions or swap partitions are not
mounted. May not be specified together with --directory=,
--template=.
--oci-bundle=
•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.
Takes the path to an OCI runtime bundle to
invoke, as specified in the OCI Runtime Specification[3]. In this case
no .nspawn file is loaded, and the root directory and various settings are
read from the OCI runtime JSON data (but data passed on the command line takes
precedence).
--read-only
Mount the container's root file system (and
any other file systems container in the container image) read-only. This has
no effect on additional mounts made with --bind=, --tmpfs= and
similar options. This mode is implied if the container image file or directory
is marked read-only itself. It is also implied if --volatile= is used.
In this case the container image on disk is strictly read-only, while changes
are permitted but kept non-persistently in memory only. For further details,
see below.
--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 writable "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 overlay the read-only root file
system is combined with a writable tmpfs instance through
"overlayfs", so that it appears at it normally would, but any
changes are applied to the temporary file system only and lost when the
container is terminated. When the mode parameter is specified as no
(the default), the whole OS tree is made available writable (unless
--read-only is specified, see above).
Note that if one of the volatile modes is chosen, its effect is limited to the
root file system (or /var/ in case of state), and any other mounts
placed in the hierarchy are unaffected — regardless if they are
established automatically (e.g. the EFI system partition that might be mounted
to /efi/ or /boot/) or explicitly (e.g. through an additional command line
option such as --bind=, see below). This means, even if
--volatile=overlay is used changes to /efi/ or /boot/ are prohibited in
case such a partition exists in the container image operated on, and even if
--volatile=state is used the hypothetical file /etc/foobar is
potentially writable if --bind=/etc/foobar if used to mount it from
outside the read-only container /etc/ directory.
The --ephemeral option is closely related to this setting, and provides
similar behaviour by making a temporary, ephemeral copy of the whole OS image
and executing that. For further details, see above.
The --tmpfs= and --overlay= options provide similar functionality,
but for specific sub-directories of the OS image only. For details, see below.
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 setting this option 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 automatically populate /var/ (and /etc/ in case
of "--volatile=yes"). Specifically, this means that operating
systems that follow the historic split of /bin/ and /lib/ (and related
directories) from /usr/ (i.e. where the former are not symlinks into the
latter) are not supported by "--volatile=yes" as container payload.
The overlay option does not require any particular preparations in the
OS, but do note that "overlayfs" behaviour differs from regular file
systems in a number of ways, and hence compatibility is limited.
--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 (except if the image has the .raw suffix, in which case the root hash
file must not have it in its name), the root hash is read from it and
automatically used, also as formatted hexadecimal characters.
Note that this configures the root hash for the root file system. Disk images
may also contain separate file systems for the /usr/ hierarchy, which may be
Verity protected as well. The root hash for this protection may be configured
via the "user.verity.usrhash" extended file attribute or via a
.usrhash file adjacent to the disk image, following the same format and logic
as for the root hash for the root file system described here. Note that
there's currently no switch to configure the root hash for the /usr/ from the
command line.
Also see the RootHash= option in systemd.exec(5).
--root-hash-sig=
Takes a PKCS7 signature of the
--root-hash= option. The semantics are the same as for the
RootHashSignature= option, see systemd.exec(5).
--verity-data=
Takes the path to a data integrity (dm-verity)
file. This option enables data integrity checks using dm-verity, if a
root-hash is passed and if the used image itself does not contains the
integrity data. The integrity data must be matched by the root hash. If this
option is not specified, but a file with the .verity suffix is found next to
the image file, bearing otherwise the same name (except if the image has the
.raw suffix, in which case the verity data file must not have it in its name),
the verity data is read from it and automatically used.
--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[4] deployments. It emulates the behavior of the
boot loader and the initrd which normally select which directory to mount as
the root and start the container's PID 1 in.
Execution Options
-a, --as-pid2Invoke 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
Note that
--boot is the default mode of operation if the [email protected]
template unit file is used.
--chdir=
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. |
Change to the specified working directory
before invoking the process in the container. Expects an absolute path in the
container's file system namespace.
-E NAME[=VALUE],
--setenv= NAME[=VALUE]
Specifies an environment variable to pass to
the init process in the container. This may be used to override the default
variables or to set additional variables. It may be used more than once to set
multiple variables. When "=" and VALUE are omitted, the value
of the variable with the same name in the program environment will be
used.
-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.
--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 abruptly via
SIGKILL. For a list of valid signals, see signal(7).
--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).
--suppress-sync=
Expects a boolean argument. If true, turns off
any form of on-disk file system synchronization for the container payload.
This means all system calls such as sync(2), fsync(),
syncfs(), ... will execute no operation, and the
O_SYNC/O_DSYNC flags to open(2) and related calls will be
made unavailable. This is potentially dangerous, as assumed data integrity
guarantees to the container payload are not actually enforced (i.e. data
assumed to have been written to disk might be lost if the system is shut down
abnormally). However, this can dramatically improve container runtime
performance – as long as these guarantees are not required or
desirable, for example because any data written by the container is of
temporary, redundant nature, or just an intermediary artifact that will be
further processed and finalized by a later step in a pipeline. Defaults to
false.
System Identity Options
-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.
Property Options
-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 the container.
--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.
User Namespacing Options
--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:
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-ownership=
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 "yes", 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. In this mode, the number of
UIDs/GIDs assigned to the container is 65536, and the owner UID/GID of the
root directory must be a multiple of 65536.
3.If the parameter is "no", user
namespacing is turned off. This is the default.
4.If the parameter is "identity",
user namespacing is employed with an identity mapping for the first 65536
UIDs/GIDs. This is mostly equivalent to --private-users=0:65536. While
it does not provide UID/GID isolation, since all host and container UIDs/GIDs
are chosen identically it does provide process capability isolation, and hence
is often a good choice if proper user namespacing with distinct UID maps is
not appropriate.
5.The special value "pick" turns on
user namespacing. In this case the UID/GID range is automatically chosen. As
first step, the file owner UID/GID of the root directory of the container's
directory tree is read, and it is checked that no other container is currently
using it. If this check is successful, the UID/GID range determined this way
is used, similarly 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, and, if possible, consistently hashed from the machine name. This
setting implies --private-users-ownership=auto (see below), which
possibly 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).
Controls how to adjust the container image's
UIDs and GIDs to match the UID/GID range chosen with --private-users=,
see above. Takes one of "off" (to leave the image as is),
"chown" (to recursively chown() the container's directory
tree as needed), "map" (in order to use transparent ID mapping
mounts) or "auto" for automatically using "map" where
available and "chown" where not.
If "chown" is selected, all files and directories in the container's
directory tree will be adjusted so that they are owned by the appropriate
UIDs/GIDs selected for the container (see above). This operation is
potentially expensive, as it involves iterating through the full directory
tree of the container. Besides actual file ownership, file ACLs are adjusted
as well.
Typically "map" is the best choice, since it transparently maps
UIDs/GIDs in memory as needed without modifying the image, and without
requiring an expensive recursive adjustment operation. However, it is not
available for all file systems, currently.
The --private-users-ownership=auto 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-ownership=auto, otherwise equivalent to
--private-users=no.
Note that -U is the default if the [email protected] template unit
file is used.
Note: it is possible to undo the effect of
--private-users-ownership=chown (or -U) on the file system by
redoing the operation with the first UID of 0:
systemd-nspawn ... --private-users=0 --private-users-ownership=chown
Networking Options
--private-networkDisconnect 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-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 calling namespace. Note that --network-interface= implies
--private-network. This option may be used more than once to add
multiple network interfaces to the container.
Note that any network interface specified this way must already exist at the
time the container is started. If the container shall be started automatically
at boot via a [email protected] unit file instance, it might hence make
sense to add a unit file drop-in to the service instance (e.g.
/etc/systemd/system/[email protected]/50-network.conf) with
contents like the following:
This will make sure that activation of the container service will be delayed
until the "ens1" network interface has shown up. This is required
since hardware probing is fully asynchronous, and network interfaces might be
discovered only later during the boot process, after the container would
normally be started without these explicit dependencies.
--network-macvlan=
[Unit] Wants=sys-subsystem-net-devices-ens1.device After=sys-subsystem-net-devices-ens1.device
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.
As with --network-interface=, the underlying Ethernet network interface
must already exist at the time the container is started, and thus similar unit
file drop-ins as described above might be useful.
--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.
As with --network-interface=, the underlying Ethernet network interface
must already exist at the time the container is started, and thus similar unit
file drop-ins as described above might be useful.
-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
/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
/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 [email protected]
template unit file is used.
Note that on Linux network interface names may have a length of 15 characters at
maximum, while container names may have a length up to 64 characters. As this
option derives the host-side interface name from the container name the name
is possibly truncated. Thus, care needs to be taken to ensure that interface
names remain unique in this case, or even better container names are generally
not chosen longer than 12 characters, to avoid the truncation. If the name is
truncated, systemd-nspawn will automatically append a 4-digit hash
value to the name to reduce the chance of collisions. However, the hash
algorithm is not collision-free. (See systemd.net-naming-scheme(7) for
details on older naming algorithms for this interface). Alternatively, the
--network-veth-extra= option may be used, which allows free
configuration of the host-side interface name independently of the container
name — but might require a bit more additional configuration in case
bridging in a fashion similar to --network-bridge= is desired.
--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-". Regardless of the used naming prefix the same
network interface name length limits imposed by Linux apply, along with the
complications this creates (for details see above).
As with --network-interface=, the underlying bridge network interface
must already exist at the time the container is started, and thus similar unit
file drop-ins as described above might be useful.
--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
/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.
--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=.
-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=.
Security Options
--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.
If the special value of "help" is passed, the program will print known
capability names and exit.
This option sets the bounding set of capabilities which also limits the ambient
capabilities as given with the --ambient-capability=.
--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).
If the special value of "help" is passed, the program will print known
capability names and exit.
This option sets the bounding set of capabilities which also limits the ambient
capabilities as given with the --ambient-capability=.
--ambient-capability=
Specify one or more additional capabilities to
pass in the inheritable and ambient set to the program started within the
container. The value "all" is not supported for this setting.
All capabilities specified here must be in the set allowed with the
--capability= and --drop-capability= options. Otherwise, an
error message will be shown.
This option cannot be combined with the boot mode of the container (as requested
via --boot).
If the special value of "help" is passed, the program will print known
capability names and exit.
--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 allow list (as opposed to a deny list!), and this
command line option hence adds or removes entries from the default allow list,
depending on the "~" prefix. Note that the applied system call
filter is also altered implicitly if additional capabilities are passed using
the --capabilities=.
-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.
Resource Options
--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.
--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.
Integration Options
--resolv-conf=Configures how /etc/resolv.conf inside of the
container shall be handled (i.e. DNS configuration synchronization from host
to container). Takes one of "off", "copy-host",
"copy-static", "copy-uplink", "copy-stub",
"replace-host", "replace-static",
"replace-uplink", "replace-stub", "bind-host",
"bind-static", "bind-uplink", "bind-stub",
"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, unless the file exists already and is not a regular
file (e.g. a symlink). Similarly, if "replace-host" is used the file
is copied, replacing any existing inode, including symlinks. Similarly, if
"bind-host" is used, the file is bind mounted from the host into the
container.
If set to "copy-static", "replace-static" or
"bind-static" the static resolv.conf file supplied with
systemd-resolved.service(8) (specifically:
/usr/lib/systemd/resolv.conf) is copied or bind mounted into the container.
If set to "copy-uplink", "replace-uplink" or
"bind-uplink" the uplink resolv.conf file managed by
systemd-resolved.service (specifically: /run/systemd/resolve/resolv.conf) is
copied or bind mounted into the container.
If set to "copy-stub", "replace-stub" or
"bind-stub" the stub resolv.conf file managed by
systemd-resolved.service (specifically: /run/systemd/resolve/stub-resolv.conf)
is copied or bind mounted into the container.
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 running its stub resolv.conf file is used, and if
not the host's /etc/resolv.conf file. In the latter cases the file is copied
if the image is writable, and bind mounted otherwise.
It's recommended to use "copy-..." or "replace-..." 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. Similarly, if "bind" is used, the file is bind mounted
from the host into the container. If set to "symlink", a symlink is
created pointing from /etc/localtime in the container to the timezone file in
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".
--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, or if the container is in the --ephemeral mode. 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
[email protected] template unit file is used.
-j
Equivalent to
--link-journal=try-guest.
Mount Options
--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. If the source path is
not absolute, it is resolved relative to the current working directory. The
--bind-ro= option creates read-only bind mounts. 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.
Mount options are comma-separated. rbind and norbind control
whether to create a recursive or a regular bind mount. Defaults to
"rbind". noidmap, idmap, and rootidmap control
ID mapping.
Using idmap or rootidmap requires support by the source filesystem
for user/group ID mapped mounts. Defaults to "noidmap". With
x being the container's UID range offset, y being the length of
the container's UID range, and p being the owner UID of the bind mount
source inode on the host:
Whichever ID mapping option is used, the same mapping will be used for users and
groups IDs. If rootidmap is used, the group owning the bind mounted
directory will have no effect
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=.
Alternatively you can use the "idmap" mount option to map the
filesystem IDs.
--bind-user=
•If noidmap is used, any user
z in the range 0 ... y seen from inside of the container is
mapped to x + z in the x ... x + y range on the host. All host
users outside of that range are mapped to nobody inside the
container.
•If idmap is used, any user
z in the UID range 0 ... y as seen from inside the container is
mapped to the same z in the same 0 ... y range on the host. All
host users outside of that range are mapped to nobody inside the
container.
•If rootidmap is used, the user
0 seen from inside of the container is mapped to p on the host.
All host users outside of that range are mapped to nobody inside the
container.
Binds the home directory of the specified user
on the host into the container. Takes the name of an existing user on the host
as argument. May be used multiple times to bind multiple users into the
container. This does three things:
The combination of the three operations above ensures that it is possible to log
into the container using the same account information as on the host. The user
is only mapped transiently, while the container is running, and the mapping
itself does not result in persistent changes to the container (except maybe
for log messages generated at login time, and similar). Note that in
particular the UID/GID assignment in the container is not made persistently.
If the user is mapped transiently, it is best to not allow the user to make
persistent changes to the container. If the user leaves files or directories
owned by the user, and those UIDs/GIDs are reused during later container
invocations (possibly with a different --bind-user= mapping), those
files and directories will be accessible to the "new" user.
The user/group record mapping only works if the container contains systemd 249
or newer, with nss-systemd properly configured in nsswitch.conf. See
nss-systemd(8) for details.
Note that the user record propagated from the host into the container will
contain the UNIX password hash of the user, so that seamless logins in the
container are possible. If the container is less trusted than the host it's
hence important to use a strong UNIX password hash function (e.g. yescrypt or
similar, with the "$y$" hash prefix).
When binding a user from the host into the container checks are executed to
ensure that the username is not yet known in the container. Moreover, it is
checked that the UID/GID allocated for it is not currently defined in the
user/group databases of the container. Both checks directly access the
container's /etc/passwd and /etc/group, and thus might not detect existing
accounts in other databases.
This operation is only supported in combination with
--private-users=/-U.
--inaccessible=
1.The user's home directory is bind mounted
from the host into /run/host/home/.
2.An additional UID/GID mapping is added that
maps the host user's UID/GID to a container UID/GID, allocated from the
60514...60577 range.
3.A JSON user and group record is generated
in /run/userdb/ that describes the mapped user. It contains a minimized
representation of the host's user record, adjusted to the UID/GID and home
directory path assigned to the user in the container. The
nss-systemd(8) glibc NSS module will pick up these records from there
and make them available in the container's user/group databases.
Make the specified path inaccessible in the
container. This over-mounts the specified path (which must exist in the
container) with a file node of the same type that is empty and has the most
restrictive access mode supported. This is an effective way to mask files,
directories and other file system objects from the container payload. This
option may be used more than once in case all specified paths are
masked.
--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). Backslash
escapes are interpreted in the path, so "\:" may be used to embed
colons in the path.
Note that this option cannot be used to replace the root file system of the
container with a temporary file system. However, the --volatile= option
described below provides similar functionality, with a focus on implementing
stateless operating system images.
--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 an 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 "--overlay=+/var::/var" in order to
automatically overlay a writable temporary directory on a read-only /var/
directory. If a source path is not absolute, it is resolved relative to the
current working directory.
For details about overlay file systems, see Overlay Filesystem[5]. 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.
Note that this option cannot be used to replace the root file system of the
container with an overlay file system. However, the --volatile= option
described above provides similar functionality, with a focus on implementing
stateless operating system images.
Input/Output Options
--console=MODEConfigures how to set up standard input,
output and error output for the container payload, as well as the /dev/console
device for the container. Takes one of interactive, read-only,
passive, pipe or autopipe. If interactive, a
pseudo-TTY is allocated and made available as /dev/console in the container.
It is then bi-directionally connected to the standard input and output passed
to systemd-nspawn. read-only is similar but only the output of
the container is propagated and no input from the caller is read. If
passive, a pseudo TTY is allocated, but it is not connected anywhere.
In pipe mode no pseudo TTY is allocated, but the standard input, output
and error output file descriptors passed to systemd-nspawn are passed
on — as they are — to the container payload, see the following
paragraph. Finally, autopipe mode operates like interactive when
systemd-nspawn is invoked on a terminal, and like pipe
otherwise. Defaults to interactive if systemd-nspawn is invoked
from a terminal, and read-only otherwise.
In pipe mode, /dev/console will not exist in the container. This means
that the container payload generally cannot be a full init system as init
systems tend to require /dev/console to be available. On the other hand, in
this mode container invocations can be used within shell pipelines. This is
because intermediary pseudo TTYs do not permit independent bidirectional
propagation of the end-of-file (EOF) condition, which is necessary for shell
pipelines to work correctly. Note that the pipe mode
should be used carefully, as passing arbitrary file descriptors to less
trusted container payloads might open up unwanted interfaces for access by the
container payload. For example, if a passed file descriptor refers to a TTY of
some form, APIs such as TIOCSTI may be used to synthesize input that
might be used for escaping the container. Hence pipe mode should only
be used if the payload is sufficiently trusted or when the standard
input/output/error output file descriptors are known safe, for example
pipes.
--pipe, -P
Equivalent to --console=pipe.
Credentials
--load-credential=ID:PATH, --set-credential=ID: VALUEPass a credential to the container. These two
options correspond to the LoadCredential= and SetCredential=
settings in unit files. See systemd.exec(5) for details about these
concepts, as well as the syntax of the option's arguments.
Note: when systemd-nspawn runs as systemd system service it can propagate
the credentials it received via LoadCredential=/SetCredential=
to the container payload. A systemd service manager running as PID 1 in the
container can further propagate them to the services it itself starts. It is
thus possible to easily propagate credentials from a parent service manager to
a container manager service and from there into its payload. This can even be
done recursively.
In order to embed binary data into the credential data for
--set-credential=, use C-style escaping (i.e. "\n" to embed a
newline, or "\x00" to embed a NUL byte). Note that the
invoking shell might already apply unescaping once, hence this might require
double escaping!.
The systemd-sysusers.service(8) and systemd-firstboot(1) services
read credentials configured this way for the purpose of configuring the
container's root user's password and shell, as well as system locale, keymap
and timezone during the first boot process of the container. This is
particularly useful in combination with --volatile=yes where every
single boot appears as first boot, since configuration applied to /etc/ is
lost on container reboot cycles. See the respective man pages for details.
Example:
The above command line will invoke the specified image file image.raw in
volatile mode, i.e. with empty /etc/ and /var/. The container payload will
recognize this as a first boot, and will invoke systemd-firstboot.service,
which then reads the two passed credentials to configure the system's initial
locale and root password.
# systemd-nspawn -i image.raw \ --volatile=yes \ --set-credential=firstboot.locale:de_DE.UTF-8 \ --set-credential=passwd.hashed-password.root:'$y$j9T$yAuRJu1o5HioZAGDYPU5d.$F64ni6J2y2nNQve90M/p0ZP0ECP/qqzipNyaY9fjGpC' \ -b
Other
--no-pagerDo not pipe output into a pager.
-h, --help
Print a short help text and exit.
--version
Print a short version string and exit.
ENVIRONMENT
$SYSTEMD_LOG_LEVELThe maximum log level of emitted messages
(messages with a higher log level, i.e. less important ones, will be
suppressed). Either one of (in order of decreasing importance) emerg,
alert, crit, err, warning, notice,
info, debug, or an integer in the range 0...7. See
syslog(3) for more information.
$SYSTEMD_LOG_COLOR
A boolean. If true, messages written to the
tty will be colored according to priority.
This setting is only useful when messages are written directly to the terminal,
because journalctl(1) and other tools that display logs will color
messages based on the log level on their own.
$SYSTEMD_LOG_TIME
A boolean. If true, console log messages will
be prefixed with a timestamp.
This setting is only useful when messages are written directly to the terminal
or a file, because journalctl(1) and other tools that display logs will
attach timestamps based on the entry metadata on their own.
$SYSTEMD_LOG_LOCATION
A boolean. If true, messages will be prefixed
with a filename and line number in the source code where the message
originates.
Note that the log location is often attached as metadata to journal entries
anyway. Including it directly in the message text can nevertheless be
convenient when debugging programs.
$SYSTEMD_LOG_TID
A boolean. If true, messages will be prefixed
with the current numerical thread ID (TID).
Note that the this information is attached as metadata to journal entries
anyway. Including it directly in the message text can nevertheless be
convenient when debugging programs.
$SYSTEMD_LOG_TARGET
The destination for log messages. One of
console (log to the attached tty), console-prefixed (log to the
attached tty but with prefixes encoding the log level and
"facility", see syslog(3), kmsg (log to the kernel
circular log buffer), journal (log to the journal),
journal-or-kmsg (log to the journal if available, and to kmsg
otherwise), auto (determine the appropriate log target automatically,
the default), null (disable log output).
$SYSTEMD_PAGER
Pager to use when --no-pager is not
given; overrides $PAGER. If neither $SYSTEMD_PAGER nor
$PAGER are set, a set of well-known pager implementations are tried in
turn, including less(1) and more(1), until one is found. If no
pager implementation is discovered no pager is invoked. Setting this
environment variable to an empty string or the value "cat" is
equivalent to passing --no-pager.
Note: if $SYSTEMD_PAGERSECURE is not set, $SYSTEMD_PAGER (as well
as $PAGER) will be silently ignored.
$SYSTEMD_LESS
Override the options passed to less (by
default "FRSXMK").
Users might want to change two options in particular:
K
Note that setting the regular $LESS environment variable has no effect
for less invocations by systemd tools.
See less(1) for more discussion.
$SYSTEMD_LESSCHARSET
This option instructs the pager to exit
immediately when Ctrl+C is pressed. To allow less to handle Ctrl+C
itself to switch back to the pager command prompt, unset this option.
If the value of $SYSTEMD_LESS does not include "K", and the
pager that is invoked is less, Ctrl+C will be ignored by the
executable, and needs to be handled by the pager.
X
This option instructs the pager to not send
termcap initialization and deinitialization strings to the terminal. It is set
by default to allow command output to remain visible in the terminal even
after the pager exits. Nevertheless, this prevents some pager functionality
from working, in particular paged output cannot be scrolled with the
mouse.
Override the charset passed to less (by
default "utf-8", if the invoking terminal is determined to be UTF-8
compatible).
Note that setting the regular $LESSCHARSET environment variable has no
effect for less invocations by systemd tools.
$SYSTEMD_PAGERSECURE
Takes a boolean argument. When true, the
"secure" mode of the pager is enabled; if false, disabled. If
$SYSTEMD_PAGERSECURE is not set at all, secure mode is enabled if the
effective UID is not the same as the owner of the login session, see
geteuid(2) and sd_pid_get_owner_uid(3). In secure mode,
LESSSECURE=1 will be set when invoking the pager, and the pager shall
disable commands that open or create new files or start new subprocesses. When
$SYSTEMD_PAGERSECURE is not set at all, pagers which are not known to
implement secure mode will not be used. (Currently only less(1)
implements secure mode.)
Note: when commands are invoked with elevated privileges, for example under
sudo(8) or pkexec(1), care must be taken to ensure that
unintended interactive features are not enabled. "Secure" mode for
the pager may be enabled automatically as describe above. Setting
SYSTEMD_PAGERSECURE=0 or not removing it from the inherited environment
allows the user to invoke arbitrary commands. Note that if the
$SYSTEMD_PAGER or $PAGER variables are to be honoured,
$SYSTEMD_PAGERSECURE must be set too. It might be reasonable to
completely disable the pager using --no-pager instead.
$SYSTEMD_COLORS
Takes a boolean argument. When true,
systemd and related utilities will use colors in their output,
otherwise the output will be monochrome. Additionally, the variable can take
one of the following special values: "16", "256" to
restrict the use of colors to the base 16 or 256 ANSI colors, respectively.
This can be specified to override the automatic decision based on $TERM
and what the console is connected to.
$SYSTEMD_URLIFY
The value must be a boolean. Controls whether
clickable links should be generated in the output for terminal emulators
supporting this. This can be specified to override the decision that
systemd makes based on $TERM and other conditions.
EXAMPLES
Example 1. Download a Fedora image and start a shell in it# machinectl pull-raw --verify=no \ https://download.fedoraproject.org/pub/fedora/linux/releases/37/Cloud/x86_64/images/Fedora-Cloud-Base-37-1.7.x86_64.raw.xz \ Fedora-Cloud-Base-37-1.7.x86-64 # systemd-nspawn -M Fedora-Cloud-Base-37-1.7.x86-64
# dnf -y --releasever=37 --installroot=/var/lib/machines/f37 \ --repo=fedora --repo=updates --setopt=install_weak_deps=False install \ passwd dnf fedora-release vim-minimal util-linux systemd systemd-networkd # systemd-nspawn -bD /var/lib/machines/f37
# debootstrap unstable ~/debian-tree/ # systemd-nspawn -D ~/debian-tree/
# pacstrap -c ~/arch-tree/ base # systemd-nspawn -bD ~/arch-tree/
# zypper --root=/var/lib/machines/tumbleweed ar -c \ https://download.opensuse.org/tumbleweed/repo/oss tumbleweed # zypper --root=/var/lib/machines/tumbleweed refresh # zypper --root=/var/lib/machines/tumbleweed install --no-recommends \ systemd shadow zypper openSUSE-release vim # systemd-nspawn -M tumbleweed passwd root # systemd-nspawn -M tumbleweed -b
# systemd-nspawn -D / -xb
# chcon system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -R /srv/container # systemd-nspawn -L system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 \ -Z system_u:system_r:svirt_lxc_net_t:s0:c0,c1 -D /srv/container /bin/sh
# systemd-nspawn -b -i ~/image.raw \ --pivot-root=/ostree/deploy/$OS/deploy/$CHECKSUM:/sysroot \ --bind=+/sysroot/ostree/deploy/$OS/var:/var
EXIT STATUS
The exit code of the program executed in the container is returned.SEE ALSO
systemd(1), systemd.nspawn(5), chroot(1), dnf(8), debootstrap(8), pacman(8), zypper(8), systemd.slice(5), machinectl(1), btrfs(8)NOTES
- 1.
- Container Interface
- 2.
- Discoverable Partitions Specification
- 3.
- OCI Runtime Specification
- 4.
- OSTree
- 5.
- Overlay Filesystem
- 6.
- Fedora
- 7.
- Debian
- 8.
- Ubuntu
- 9.
- Tanglu
- 10.
- Arch Linux
- 11.
- OpenSUSE Tumbleweed
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