systemd.nspawn(5)
NAME
systemd.nspawn - Container settings
SYNOPSIS
/etc/systemd/nspawn/machine.nspawn /run/systemd/nspawn/machine.nspawn /var/lib/machines/machine.nspawn
DESCRIPTION
An nspawn container settings file (suffix .nspawn) encodes additional runtime information about a local container, and is searched, read and used by systemd-nspawn(1) when starting a container. Files of this type are named after the containers they define settings for. They are optional, and only required for containers whose execution environment shall differ from the defaults. Files of this type mostly contain settings that may also be set on the systemd-nspawn command line, and make it easier to persistently attach specific settings to specific containers. The syntax of these files is inspired by .desktop files following the XDG Desktop Entry Specification[1], which in turn are inspired by Microsoft Windows .ini files. Boolean arguments used in these settings files can be written in various formats. For positive settings, the strings 1, yes, true and on are equivalent. For negative settings, the strings 0, no, false and off are equivalent. Empty lines and lines starting with # or ; are ignored. This may be used for commenting. Lines ending in a backslash are concatenated with the following line while reading and the backslash is replaced by a space character. This may be used to wrap long lines.
.NSPAWN FILE DISCOVERY
Files are searched by appending the .nspawn suffix to the machine name of the container, as specified with the --machine= switch of systemd-nspawn, or derived from the directory or image file name. This file is first searched in /etc/systemd/nspawn/ and /run/systemd/nspawn/. If found in these directories, its settings are read and all of them take full effect (but are possibly overridden by corresponding command line arguments). If not found, the file will then be searched next to the image file or in the immediate parent of the root directory of the container. If the file is found there, only a subset of the settings will take effect however. All settings that possibly elevate privileges or grant additional access to resources of the host (such as files or directories) are ignored. To which options this applies is documented below. Persistent settings files created and maintained by the administrator (and thus trusted) should be placed in /etc/systemd/nspawn/, while automatically downloaded (and thus potentially untrusted) settings files are placed in /var/lib/machines/ instead (next to the container images), where their security impact is limited. In order to add privileged settings to .nspawn files acquired from the image vendor, it is recommended to copy the settings files into /etc/systemd/nspawn/ and edit them there, so that the privileged options become available. The precise algorithm for how the files are searched and interpreted may be configured with systemd-nspawn's --settings= switch, see systemd- nspawn(1) for details.
[EXEC] SECTION OPTIONS
Settings files may include an "[Exec]" section, which carries various
execution parameters:
Boot=
Takes a boolean argument, which defaults to off. If enabled,
systemd-nspawn will automatically search for an init executable and
invoke it. In this case, the specified parameters using Parameters=
are passed as additional arguments to the init process. This
setting corresponds to the --boot switch on the systemd-nspawn
command line. This option may not be combined with ProcessTwo=yes.
This option is the default if the systemd-nspawn@.service template
unit file is used.
ProcessTwo=
Takes a boolean argument, which defaults to off. If enabled, the
specified program is run as PID 2. A stub init process is run as
PID 1. This setting corresponds to the --as-pid2 switch on the
systemd-nspawn command line. This option may not be combined with
Boot=yes.
Parameters=
Takes a space-separated list of arguments. This is either a command
line, beginning with the binary name to execute, or -- if Boot= is
enabled -- the list of arguments to pass to the init process. This
setting corresponds to the command line parameters passed on the
systemd-nspawn command line.
Environment=
Takes an environment variable assignment consisting of key and
value, separated by "=". Sets an environment variable for the main
process invoked in the container. This setting may be used multiple
times to set multiple environment variables. It corresponds to the
--setenv= command line switch.
User=
Takes a UNIX user name. Specifies the user name to invoke the main
process of the container as. This user must be known in the
container's user database. This corresponds to the --user= command
line switch.
WorkingDirectory=
Selects the working directory for the process invoked in the
container. Expects an absolute path in the container's file system
namespace. This corresponds to the --chdir= command line switch.
Capability=, DropCapability=
Takes a space-separated list of Linux process capabilities (see
capabilities(7) for details). The Capability= setting specifies
additional capabilities to pass on top of the default set of
capabilities. The DropCapability= setting specifies capabilities to
drop from the default set. These settings correspond to the
--capability= and --drop-capability= command line switches. Note
that Capability= is a privileged setting, and only takes effect in
.nspawn files in /etc/systemd/nspawn/ and /run/system/nspawn/ (see
above). On the other hand, DropCapability= takes effect in all
cases.
KillSignal=
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). For a list of valid signals, see signal(7).
Personality=
Configures the kernel personality for the container. This is
equivalent to the --personality= switch.
MachineID=
Configures the 128-bit machine ID (UUID) to pass to the container.
This is equivalent to the --uuid= command line switch. This option
is privileged (see above).
PrivateUsers=
Configures support for usernamespacing. This is equivalent to the
--private-users= command line switch, and takes the same options.
This option is privileged (see above). This option is the default
if the systemd-nspawn@.service template unit file is used.
NotifyReady=
Configures support for notifications from the container's init
process. This is equivalent to use --notify-ready= command line
switch, and takes the same options. See systemd-nspawn(1) for
details about the specific options supported.
[FILES] SECTION OPTIONS
Settings files may include a "[Files]" section, which carries various
parameters configuring the file system of the container:
ReadOnly=
Takes a boolean argument, which defaults to off. If specified, the
container will be run with a read-only file system. This setting
corresponds to the --read-only command line switch.
Volatile=
Takes a boolean argument, or the special value "state". This
configures whether to run the container with volatile state and/or
configuration. This option is equivalent to --volatile=, see
systemd-nspawn(1) for details about the specific options supported.
Bind=, BindReadOnly=
Adds a bind mount from the host into the container. Takes a single
path, a pair of two paths separated by a colon, or a triplet of two
paths plus an option string separated by colons. This option may be
used multiple times to configure multiple bind mounts. This option
is equivalent to the command line switches --bind= and --bind-ro=,
see systemd-nspawn(1) for details about the specific options
supported. This setting is privileged (see above).
TemporaryFileSystem=
Adds a "tmpfs" mount to the container. Takes a path or a pair of
path and option string, separated by a colon. This option may be
used multiple times to configure multiple "tmpfs" mounts. This
option is equivalent to the command line switch --tmpfs=, see
systemd-nspawn(1) for details about the specific options supported.
This setting is privileged (see above).
PrivateUsersChown=
Configures whether the ownership of the files and directories in
the container tree shall be adjusted to the UID/GID range used, if
necessary and user namespacing is enabled. This is equivalent to
the --private-users-chown command line switch. This option is
privileged (see above).
[NETWORK] SECTION OPTIONS
Settings files may include a "[Network]" section, which carries various
parameters configuring the network connectivity of the container:
Private=
Takes a boolean argument, which defaults to off. If enabled, the
container will run in its own network namespace and not share
network interfaces and configuration with the host. This setting
corresponds to the --private-network command line switch.
VirtualEthernet=
Takes a boolean argument. Configures whether to create a virtual
Ethernet connection ("veth") between host and the container. This
setting implies Private=yes. This setting corresponds to the
--network-veth command line switch. This option is privileged (see
above). This option is the default if the systemd-nspawn@.service
template unit file is used.
VirtualEthernetExtra=
Takes a colon-separated pair of interface names. Configures an
additional virtual Ethernet connection ("veth") between host and
the container. The first specified name is the interface name on
the host, the second the interface name in the container. The
latter may be omitted in which case it is set to the same name as
the host side interface. This setting implies Private=yes. This
setting corresponds to the --network-veth-extra= command line
switch, and maybe be used multiple times. It is independent of
VirtualEthernet=. This option is privileged (see above).
Interface=
Takes a space-separated list of interfaces to add to the container.
This option corresponds to the --network-interface= command line
switch and implies Private=yes. This option is privileged (see
above).
MACVLAN=, IPVLAN=
Takes a space-separated list of interfaces to add MACLVAN or IPVLAN
interfaces to, which are then added to the container. These options
correspond to the --network-macvlan= and --network-ipvlan= command
line switches and imply Private=yes. These options are privileged
(see above).
Bridge=
Takes an interface name. This setting implies VirtualEthernet=yes
and Private=yes and has the effect that the host side of the
created virtual Ethernet link is connected to the specified bridge
interface. This option corresponds to the --network-bridge= command
line switch. This option is privileged (see above).
Zone=
Takes a network zone name. This setting implies VirtualEthernet=yes
and Private=yes and has the effect that the host side of the
created virtual Ethernet link is connected to an automatically
managed bridge interface named after the passed argument, prefixed
with "vz-". This option corresponds to the --network-zone= command
line switch. This option is privileged (see above).
Port=
Exposes a TCP or UDP port of the container on the host. This option
corresponds to the --port= command line switch, see systemd-
nspawn(1) for the precise syntax of the argument this option takes.
This option is privileged (see above).
SEE ALSO
systemd(1), systemd-nspawn(1), systemd.directives(7)
NOTES
1. XDG Desktop Entry Specification
http://standards.freedesktop.org/desktop-entry-spec/latest/
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