systemd.nspawn — Container settings
/etc/systemd/nspawn/machine.nspawn
/run/systemd/nspawn/machine.nspawn
/var/lib/machines/machine.nspawn
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, 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.
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.
PivotRoot=¶Selects a directory to pivot to / inside the container when starting up.
Takes a single path, or a pair of two paths separated by a colon. Both paths must be absolute, and are resolved
in the container's file system namespace. This corresponds to the --pivot-root= 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.
NoNewPrivileges=¶Takes a boolean argument that controls the PR_SET_NO_NEW_PRIVS flag for
the container payload. This is equivalent to the
--no-new-privileges= command line switch. See
systemd-nspawn(1) for
details.
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
the --notify-ready= command line switch, and takes the same parameters. See
systemd-nspawn(1) for details
about the specific options supported.
SystemCallFilter=¶Configures the system call filter applied to containers. This is equivalent to the
--system-call-filter= command line switch, and takes the same list parameter. See
systemd-nspawn(1) for
details.
LimitCPU=, LimitFSIZE=, LimitDATA=, LimitSTACK=, LimitCORE=, LimitRSS=, LimitNOFILE=, LimitAS=, LimitNPROC=, LimitMEMLOCK=, LimitLOCKS=, LimitSIGPENDING=, LimitMSGQUEUE=, LimitNICE=, LimitRTPRIO=, LimitRTTIME=¶Configures various types of resource limits applied to containers. This is equivalent to the
--rlimit= command line switch, and takes the same arguments. See
systemd-nspawn(1) for
details.
OOMScoreAdjust=¶Configures the OOM score adjustment value. This is equivalent to the
--oom-score-adjust= command line switch, and takes the same argument. See
systemd-nspawn(1) for
details.
CPUAffinity=¶Configures the CPU affinity. This is equivalent to the --cpu-affinity= command
line switch, and takes the same argument. See
systemd-nspawn(1) for
details.
Hostname=¶Configures the kernel hostname set for the container. This is equivalent to the
--hostname= command line switch, and takes the same argument. See
systemd-nspawn(1) for
details.
ResolvConf=¶Configures how /etc/resolv.conf in the container shall be handled. This is
equivalent to the --resolv-conf= command line switch, and takes the same argument. See
systemd-nspawn(1) for
details.
Timezone=¶Configures how /etc/localtime in the container shall be handled. This is
equivalent to the --localtime= command line switch, and takes the same argument. See
systemd-nspawn(1) for
details.
LinkJournal=¶Configures how to link host and container journal setups. This is equivalent to the
--link-journal= command line switch, and takes the same parameter. See
systemd-nspawn(1) for
details.
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).
Overlay=, OverlayReadOnly=¶Adds an overlay mount point. Takes a colon-separated list of paths. This option may be used
multiple times to configure multiple overlay mounts. This option is equivalent to the command line switches
--overlay= and --overlay-ro=, 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).
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).