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).
NOTES¶
- 1.
- XDG Desktop Entry Specification