SYSTEMD.NSPAWN(5) systemd.nspawn 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) contains runtime
configuration for a local container, and is used by systemd-nspawn(1).
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, similarly to other configuration files supported by the systemd
project. See systemd.syntax(7) for an overview.
.NSPAWN FILE DISCOVERY
Files are searched for 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 for in /etc/systemd/nspawn/ and
/run/systemd/nspawn/. If found there, the settings are read and all of
them take full effect (but may still be overridden by corresponding
command line arguments). Otherwise, the file will then be searched for
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
specified by default in the systemd-nspawn@.service template unit.
Added in version 226.
Ephemeral=
Takes a boolean argument, which defaults to off, If enabled, the
container is run with a temporary snapshot of its file system that
is removed immediately when the container terminates. This is
equivalent to the --ephemeral command line switch. See systemd-
nspawn(1) for details about the specific options supported.
Added in version 240.
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.
Added in version 229.
Parameters=
Takes a whitespace-separated list of arguments. Single ("'") and
double (""") quotes may be used around arguments with whitespace.
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.
Note: Boot=no, Parameters=a b "c c" is the same as systemd-nspawn a
b "c c", and Boot=yes, Parameters=b 'c c' is the same as
systemd-nspawn --boot b 'c c'.
Added in version 226.
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.
Added in version 226.
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.
Added in version 226.
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.
Added in version 229.
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.
Added in version 233.
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. If the special value "all" is passed, all capabilities are
retained (or dropped).
These settings change the bounding set of capabilities which also
limits the ambient capabilities as given with the
AmbientCapability=.
Added in version 226.
AmbientCapability=
Takes a space-separated list of Linux process capabilities (see
capabilities(7) for details). The AmbientCapability= setting
specifies capabilities which will be passed to the started program
in the inheritable and ambient capability sets. This will grant
these capabilities to this process. This setting correspond to the
--ambient-capability= command line switch.
The value "all" is not supported for this setting.
The setting of AmbientCapability= must be covered by the bounding
set settings which were established by Capability= and
DropCapability=.
Note that AmbientCapability= is a privileged setting (see above).
Added in version 248.
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.
Added in version 239.
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).
Added in version 230.
Personality=
Configures the kernel personality for the container. This is
equivalent to the --personality= switch.
Added in version 226.
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).
Added in version 226.
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.
Added in version 230.
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.
Added in version 231.
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.
Added in version 235.
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.
Added in version 239.
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.
Added in version 239.
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.
Added in version 239.
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.
Added in version 239.
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.
Added in version 239.
Timezone=
Configures how /etc/localtime in the container shall be handled.
This is equivalent to the --timezone= command line switch, and takes
the same argument. See systemd-nspawn(1) for details.
Added in version 239.
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.
Added in version 239.
SuppressSync=
Configures whether to suppress disk synchronization for the
container payload. This is equivalent to the --suppress-sync=
command line switch, and takes the same parameter. See systemd-
nspawn(1) for details.
Added in version 250.
[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.
Added in version 226.
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.
Added in version 226.
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).
Added in version 226.
BindUser=
Binds a user from the host into the container. This option is
equivalent to the command line switch --bind-user=, see systemd-
nspawn(1) for details about the specific options supported. This
setting is privileged (see above).
Added in version 249.
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).
Added in version 226.
Inaccessible=
Masks the specified file or directory in the container, by
over-mounting it with an empty file node of the same type with the
most restrictive access mode. Takes a file system path as argument.
This option may be used multiple times to mask multiple files or
directories. This option is equivalent to the command line switch
--inaccessible=, see systemd-nspawn(1) for details about the
specific options supported. This setting is privileged (see above).
Added in version 242.
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).
Added in version 233.
PrivateUsersOwnership=
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-ownership= command line switch. This option is
privileged (see above).
Added in version 249.
[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.
Added in version 226.
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.
Added in version 226.
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
may be used multiple times. It is independent of VirtualEthernet=.
Note that this option is unrelated to the Bridge= setting below, and
thus any connections created this way are not automatically added to
any bridge device on the host side. This option is privileged (see
above).
Added in version 228.
Interface=
Takes a space-separated list of interfaces to add to the container.
The interface object is defined either by a single interface name,
referencing the name on the host, or a colon-separated pair of
interfaces, in which case the first one references the name on the
host, and the second one the name in the container. This option
corresponds to the --network-interface= command line switch and
implies Private=yes. This option is privileged (see above).
Added in version 226.
MACVLAN=, IPVLAN=
Takes a space-separated list of interfaces to add MACLVAN or IPVLAN
interfaces to, which are then added to the container. The interface
object is defined either by a single interface name, referencing the
name on the host, or a colon-separated pair of interfaces, in which
case the first one references the name on the host, and the second
one the name in 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).
Added in version 226.
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).
Added in version 226.
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).
Added in version 230.
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).
Added in version 226.
SEE ALSO
systemd(1), systemd-nspawn(1), systemd.directives(7)
systemd 257.9 SYSTEMD.NSPAWN(5)
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