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7 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
9 <refentry id=
"systemd.nspawn">
12 <title>systemd.nspawn
</title>
13 <productname>systemd
</productname>
17 <refentrytitle>systemd.nspawn
</refentrytitle>
18 <manvolnum>5</manvolnum>
22 <refname>systemd.nspawn
</refname>
23 <refpurpose>Container settings
</refpurpose>
27 <para><filename>/etc/systemd/nspawn/
<replaceable>machine
</replaceable>.nspawn
</filename></para>
28 <para><filename>/run/systemd/nspawn/
<replaceable>machine
</replaceable>.nspawn
</filename></para>
29 <para><filename>/var/lib/machines/
<replaceable>machine
</replaceable>.nspawn
</filename></para>
33 <title>Description
</title>
35 <para>An nspawn container settings file (suffix
<filename>.nspawn
</filename>) contains runtime
36 configuration for a local container, and is used by
37 <citerefentry><refentrytitle>systemd-nspawn
</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
38 Files of this type are named after the containers they define settings for. They are optional, and only
39 required for containers whose execution environment shall differ from the defaults. Files of this type
40 mostly contain settings that may also be set on the
<command>systemd-nspawn
</command> command line, and
41 make it easier to persistently attach specific settings to specific containers. The syntax of these files
42 is inspired by
<filename>.desktop
</filename> files, similarly to other configuration files supported by
43 the systemd project. See
44 <citerefentry><refentrytitle>systemd.syntax
</refentrytitle><manvolnum>7</manvolnum></citerefentry> for an
49 <title><filename>.nspawn
</filename> File Discovery
</title>
51 <para>Files are searched for by appending the
<filename>.nspawn
</filename> suffix to the machine name of
52 the container, as specified with the
<option>--machine=
</option> switch of
53 <command>systemd-nspawn
</command>, or derived from the directory or image file name. This file is first
54 searched for in
<filename>/etc/systemd/nspawn/
</filename> and
55 <filename>/run/systemd/nspawn/
</filename>. If found there, the settings are read and all of them take
56 full effect (but may still be overridden by corresponding command line arguments). Otherwise, the file
57 will then be searched for next to the image file or in the immediate parent of the root directory of the
58 container. If the file is found there, only a subset of the settings will take effect however. All
59 settings that possibly elevate privileges or grant additional access to resources of the host (such as
60 files or directories) are ignored. To which options this applies is documented below.
</para>
62 <para>Persistent settings files created and maintained by the
63 administrator (and thus trusted) should be placed in
64 <filename>/etc/systemd/nspawn/
</filename>, while automatically
65 downloaded (and thus potentially untrusted) settings files are
66 placed in
<filename>/var/lib/machines/
</filename> instead (next to
67 the container images), where their security impact is limited. In
68 order to add privileged settings to
<filename>.nspawn
</filename>
69 files acquired from the image vendor, it is recommended to copy the
70 settings files into
<filename>/etc/systemd/nspawn/
</filename> and
71 edit them there, so that the privileged options become
72 available. The precise algorithm for how the files are searched and
73 interpreted may be configured with
74 <command>systemd-nspawn
</command>'s
<option>--settings=
</option>
76 <citerefentry><refentrytitle>systemd-nspawn
</refentrytitle><manvolnum>1</manvolnum></citerefentry>
81 <title>[Exec] Section Options
</title>
83 <para>Settings files may include an [Exec]
84 section, which carries various execution parameters:
</para>
86 <variablelist class='nspawn-directives'
>
89 <term><varname>Boot=
</varname></term>
91 <listitem><para>Takes a boolean argument, which defaults to off. If enabled,
<command>systemd-nspawn
</command>
92 will automatically search for an
<filename>init
</filename> executable and invoke it. In this case, the
93 specified parameters using
<varname>Parameters=
</varname> are passed as additional arguments to the
94 <filename>init
</filename> process. This setting corresponds to the
<option>--boot
</option> switch on the
95 <command>systemd-nspawn
</command> command line. This option may not be combined with
96 <varname>ProcessTwo=yes
</varname>. This option is specified by default in the
97 <filename>systemd-nspawn@.service
</filename> template unit.
</para></listitem>
101 <term><varname>Ephemeral=
</varname></term>
103 <listitem><para>Takes a boolean argument, which defaults to off, If enabled, the container is run with
104 a temporary snapshot of its file system that is removed immediately when the container terminates.
105 This is equivalent to the
<option>--ephemeral
</option> command line switch. See
106 <citerefentry><refentrytitle>systemd-nspawn
</refentrytitle><manvolnum>1</manvolnum></citerefentry> for details
107 about the specific options supported.
</para></listitem>
111 <term><varname>ProcessTwo=
</varname></term>
113 <listitem><para>Takes a boolean argument, which defaults to off. If enabled, the specified program is run as
114 PID
2. A stub init process is run as PID
1. This setting corresponds to the
<option>--as-pid2
</option> switch
115 on the
<command>systemd-nspawn
</command> command line. This option may not be combined with
116 <varname>Boot=yes
</varname>.
</para></listitem>
120 <term><varname>Parameters=
</varname></term>
122 <listitem><para>Takes a whitespace-separated list of arguments. Single (
<literal>'
</literal>) and
123 double (
<literal>"</literal>) quotes may be used around arguments with whitespace. This is either a
124 command line, beginning with the binary name to execute, or – if <varname>Boot=</varname> is enabled
125 – the list of arguments to pass to the init process. This setting corresponds to the command line
126 parameters passed on the <command>systemd-nspawn</command> command line.</para>
128 <para>Note: <option>Boot=no</option>, <option>Parameters=a b "c c
"</option> is the same as
129 <command>systemd-nspawn a b "c c
"</command>, and <option>Boot=yes</option>, <option>Parameters=b 'c c'</option>
130 is the same as <command>systemd-nspawn --boot b 'c c'</command>.</para></listitem>
134 <term><varname>Environment=</varname></term>
136 <listitem><para>Takes an environment variable assignment
137 consisting of key and value, separated by
138 <literal>=</literal>. Sets an environment variable for the
139 main process invoked in the container. This setting may be
140 used multiple times to set multiple environment variables. It
141 corresponds to the <option>--setenv=</option> command line
142 switch.</para></listitem>
146 <term><varname>User=</varname></term>
148 <listitem><para>Takes a UNIX user name. Specifies the user
149 name to invoke the main process of the container as. This user
150 must be known in the container's user database. This
151 corresponds to the <option>--user=</option> command line
152 switch.</para></listitem>
156 <term><varname>WorkingDirectory=</varname></term>
158 <listitem><para>Selects the working directory for the process invoked in the container. Expects an absolute
159 path in the container's file system namespace. This corresponds to the <option>--chdir=</option> command line
160 switch.</para></listitem>
164 <term><varname>PivotRoot=</varname></term>
166 <listitem><para>Selects a directory to pivot to <filename>/</filename> inside the container when starting up.
167 Takes a single path, or a pair of two paths separated by a colon. Both paths must be absolute, and are resolved
168 in the container's file system namespace. This corresponds to the <option>--pivot-root=</option> command line
169 switch.</para></listitem>
173 <term><varname>Capability=</varname></term>
174 <term><varname>DropCapability=</varname></term>
176 <listitem><para>Takes a space-separated list of Linux process
178 <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
179 for details). The <varname>Capability=</varname> setting
180 specifies additional capabilities to pass on top of the
181 default set of capabilities. The
182 <varname>DropCapability=</varname> setting specifies
183 capabilities to drop from the default set. These settings
184 correspond to the <option>--capability=</option> and
185 <option>--drop-capability=</option> command line
186 switches. Note that <varname>Capability=</varname> is a
187 privileged setting, and only takes effect in
188 <filename>.nspawn</filename> files in
189 <filename>/etc/systemd/nspawn/</filename> and
190 <filename>/run/system/nspawn/</filename> (see above). On the
191 other hand, <varname>DropCapability=</varname> takes effect in
192 all cases. If the special value <literal>all</literal> is passed, all
193 capabilities are retained (or dropped).</para>
194 <para>These settings change the bounding set of capabilities which
195 also limits the ambient capabilities as given with the
196 <varname>AmbientCapability=</varname>.</para></listitem>
200 <term><varname>AmbientCapability=</varname></term>
201 <listitem><para>Takes a space-separated list of Linux process
203 <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
204 for details). The <varname>AmbientCapability=</varname> setting
205 specifies capability which will be passed to the started program
206 in the inheritable and ambient capability sets. This will grant
207 these capabilities to this process. This setting correspond to
208 the <option>--ambient-capability=</option> command line switch.
211 <para>The value <literal>all</literal> is not supported for this
214 <para>The setting of <varname>AmbientCapability=</varname> must
215 be covered by the bounding set settings which were established by
216 <varname>Capability=</varname> and <varname>DropCapability=</varname>.
219 <para>Note that <varname>AmbientCapability=</varname> is a privileged
220 setting (see above).</para></listitem>
224 <term><varname>NoNewPrivileges=</varname></term>
226 <listitem><para>Takes a boolean argument that controls the <constant>PR_SET_NO_NEW_PRIVS</constant> flag for
227 the container payload. This is equivalent to the
228 <option>--no-new-privileges=</option> command line switch. See
229 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
235 <term><varname>KillSignal=</varname></term>
237 <listitem><para>Specify the process signal to send to the
238 container's PID 1 when nspawn itself receives SIGTERM, in
239 order to trigger an orderly shutdown of the container.
240 Defaults to SIGRTMIN+3 if <option>Boot=</option> is used
241 (on systemd-compatible init systems SIGRTMIN+3 triggers an
242 orderly shutdown). For a list of valid signals, see
243 <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem>
247 <term><varname>Personality=</varname></term>
249 <listitem><para>Configures the kernel personality for the
250 container. This is equivalent to the
251 <option>--personality=</option> switch.</para></listitem>
255 <term><varname>MachineID=</varname></term>
257 <listitem><para>Configures the 128-bit machine ID (UUID) to pass to
258 the container. This is equivalent to the
259 <option>--uuid=</option> command line switch. This option is
260 privileged (see above). </para></listitem>
264 <term><varname>PrivateUsers=</varname></term>
266 <listitem><para>Configures support for usernamespacing. This is equivalent to the
267 <option>--private-users=</option> command line switch, and takes the same options. This option is privileged
268 (see above). This option is the default if the <filename>systemd-nspawn@.service</filename> template unit file
269 is used.</para></listitem>
273 <term><varname>NotifyReady=</varname></term>
275 <listitem><para>Configures support for notifications from the container's init process. This is equivalent to
276 the <option>--notify-ready=</option> command line switch, and takes the same parameters. See
277 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry> for details
278 about the specific options supported.</para></listitem>
282 <term><varname>SystemCallFilter=</varname></term>
284 <listitem><para>Configures the system call filter applied to containers. This is equivalent to the
285 <option>--system-call-filter=</option> command line switch, and takes the same list parameter. See
286 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
287 details.</para></listitem>
291 <term><varname>LimitCPU=</varname></term>
292 <term><varname>LimitFSIZE=</varname></term>
293 <term><varname>LimitDATA=</varname></term>
294 <term><varname>LimitSTACK=</varname></term>
295 <term><varname>LimitCORE=</varname></term>
296 <term><varname>LimitRSS=</varname></term>
297 <term><varname>LimitNOFILE=</varname></term>
298 <term><varname>LimitAS=</varname></term>
299 <term><varname>LimitNPROC=</varname></term>
300 <term><varname>LimitMEMLOCK=</varname></term>
301 <term><varname>LimitLOCKS=</varname></term>
302 <term><varname>LimitSIGPENDING=</varname></term>
303 <term><varname>LimitMSGQUEUE=</varname></term>
304 <term><varname>LimitNICE=</varname></term>
305 <term><varname>LimitRTPRIO=</varname></term>
306 <term><varname>LimitRTTIME=</varname></term>
308 <listitem><para>Configures various types of resource limits applied to containers. This is equivalent to the
309 <option>--rlimit=</option> command line switch, and takes the same arguments. See
310 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
311 details.</para></listitem>
315 <term><varname>OOMScoreAdjust=</varname></term>
317 <listitem><para>Configures the OOM score adjustment value. This is equivalent to the
318 <option>--oom-score-adjust=</option> command line switch, and takes the same argument. See
319 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
320 details.</para></listitem>
324 <term><varname>CPUAffinity=</varname></term>
326 <listitem><para>Configures the CPU affinity. This is equivalent to the <option>--cpu-affinity=</option> command
327 line switch, and takes the same argument. See
328 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
329 details.</para></listitem>
333 <term><varname>Hostname=</varname></term>
335 <listitem><para>Configures the kernel hostname set for the container. This is equivalent to the
336 <option>--hostname=</option> command line switch, and takes the same argument. See
337 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
338 details.</para></listitem>
342 <term><varname>ResolvConf=</varname></term>
344 <listitem><para>Configures how <filename>/etc/resolv.conf</filename> in the container shall be handled. This is
345 equivalent to the <option>--resolv-conf=</option> command line switch, and takes the same argument. See
346 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
347 details.</para></listitem>
351 <term><varname>Timezone=</varname></term>
353 <listitem><para>Configures how <filename>/etc/localtime</filename> in the container shall be handled. This is
354 equivalent to the <option>--timezone=</option> command line switch, and takes the same argument. See
355 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
356 details.</para></listitem>
360 <term><varname>LinkJournal=</varname></term>
362 <listitem><para>Configures how to link host and container journal setups. This is equivalent to the
363 <option>--link-journal=</option> command line switch, and takes the same parameter. See
364 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
365 details.</para></listitem>
369 <term><varname>SuppressSync=</varname></term>
371 <listitem><para>Configures whether to suppress disk synchronization for the container payload. This
372 is equivalent to the <option>--suppress-sync=</option> command line switch, and takes the same
374 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
375 for details.</para></listitem>
382 <title>[Files] Section Options</title>
384 <para>Settings files may include a [Files]
385 section, which carries various parameters configuring the file
386 system of the container:</para>
388 <variablelist class='nspawn-directives'>
391 <term><varname>ReadOnly=</varname></term>
393 <listitem><para>Takes a boolean argument, which defaults to off. If
394 specified, the container will be run with a read-only file
395 system. This setting corresponds to the
396 <option>--read-only</option> command line
397 switch.</para></listitem>
401 <term><varname>Volatile=</varname></term>
403 <listitem><para>Takes a boolean argument, or the special value
404 <literal>state</literal>. This configures whether to run the
405 container with volatile state and/or configuration. This
406 option is equivalent to <option>--volatile=</option>, see
407 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
408 for details about the specific options
409 supported.</para></listitem>
413 <term><varname>Bind=</varname></term>
414 <term><varname>BindReadOnly=</varname></term>
416 <listitem><para>Adds a bind mount from the host into the
417 container. Takes a single path, a pair of two paths separated
418 by a colon, or a triplet of two paths plus an option string
419 separated by colons. This option may be used multiple times to
420 configure multiple bind mounts. This option is equivalent to
421 the command line switches <option>--bind=</option> and
422 <option>--bind-ro=</option>, see
423 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
424 for details about the specific options supported. This setting
425 is privileged (see above).</para></listitem>
429 <term><varname>BindUser=</varname></term>
431 <listitem><para>Binds a user from the host into the container. This option is equivalent to the
432 command line switch <option>--bind-user=</option>, see
433 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
434 for details about the specific options supported. This setting is privileged (see
435 above).</para></listitem>
439 <term><varname>TemporaryFileSystem=</varname></term>
441 <listitem><para>Adds a <literal>tmpfs</literal> mount to the
442 container. Takes a path or a pair of path and option string,
443 separated by a colon. This option may be used multiple times to
444 configure multiple <literal>tmpfs</literal> mounts. This
445 option is equivalent to the command line switch
446 <option>--tmpfs=</option>, see
447 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
448 for details about the specific options supported. This setting
449 is privileged (see above).</para></listitem>
453 <term><varname>Inaccessible=</varname></term>
455 <listitem><para>Masks the specified file or directory in the container, by over-mounting it with an empty file
456 node of the same type with the most restrictive access mode. Takes a file system path as argument. This option
457 may be used multiple times to mask multiple files or directories. This option is equivalent to the command line
458 switch <option>--inaccessible=</option>, see
459 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry> for details
460 about the specific options supported. This setting is privileged (see above).</para></listitem>
464 <term><varname>Overlay=</varname></term>
465 <term><varname>OverlayReadOnly=</varname></term>
467 <listitem><para>Adds an overlay mount point. Takes a colon-separated list of paths. This option may be used
468 multiple times to configure multiple overlay mounts. This option is equivalent to the command line switches
469 <option>--overlay=</option> and <option>--overlay-ro=</option>, see
470 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry> for details
471 about the specific options supported. This setting is privileged (see above).</para></listitem>
475 <term><varname>PrivateUsersOwnership=</varname></term>
477 <listitem><para>Configures whether the ownership of the files and directories in the container tree
478 shall be adjusted to the UID/GID range used, if necessary and user namespacing is enabled. This is
479 equivalent to the <option>--private-users-ownership=</option> command line switch. This option is
480 privileged (see above).</para></listitem>
487 <title>[Network] Section Options</title>
489 <para>Settings files may include a [Network]
490 section, which carries various parameters configuring the network
491 connectivity of the container:</para>
493 <variablelist class='nspawn-directives'>
496 <term><varname>Private=</varname></term>
498 <listitem><para>Takes a boolean argument, which defaults to off. If
499 enabled, the container will run in its own network namespace
500 and not share network interfaces and configuration with the
501 host. This setting corresponds to the
502 <option>--private-network</option> command line
503 switch.</para></listitem>
507 <term><varname>VirtualEthernet=</varname></term>
509 <listitem><para>Takes a boolean argument. Configures whether to create a virtual Ethernet connection
510 (<literal>veth</literal>) between host and the container. This setting implies
511 <varname>Private=yes</varname>. This setting corresponds to the <option>--network-veth</option> command line
512 switch. This option is privileged (see above). This option is the default if the
513 <filename>systemd-nspawn@.service</filename> template unit file is used.</para></listitem>
517 <term><varname>VirtualEthernetExtra=</varname></term>
519 <listitem><para>Takes a colon-separated pair of interface names. Configures an additional virtual
520 Ethernet connection (<literal>veth</literal>) between host and the container. The first specified
521 name is the interface name on the host, the second the interface name in the container. The latter
522 may be omitted in which case it is set to the same name as the host side interface. This setting
523 implies <varname>Private=yes</varname>. This setting corresponds to the
524 <option>--network-veth-extra=</option> command line switch, and maybe be used multiple times. It is
525 independent of <varname>VirtualEthernet=</varname>. Note that this option is unrelated to the
526 <varname>Bridge=</varname> setting below, and thus any connections created this way are not
527 automatically added to any bridge device on the host side. This option is privileged (see
528 above).</para></listitem>
532 <term><varname>Interface=</varname></term>
534 <listitem><para>Takes a space-separated list of interfaces to
535 add to the container. This option corresponds to the
536 <option>--network-interface=</option> command line switch and
537 implies <varname>Private=yes</varname>. This option is
538 privileged (see above).</para></listitem>
542 <term><varname>MACVLAN=</varname></term>
543 <term><varname>IPVLAN=</varname></term>
545 <listitem><para>Takes a space-separated list of interfaces to
546 add MACLVAN or IPVLAN interfaces to, which are then added to
547 the container. These options correspond to the
548 <option>--network-macvlan=</option> and
549 <option>--network-ipvlan=</option> command line switches and
550 imply <varname>Private=yes</varname>. These options are
551 privileged (see above).</para></listitem>
555 <term><varname>Bridge=</varname></term>
557 <listitem><para>Takes an interface name. This setting implies
558 <varname>VirtualEthernet=yes</varname> and
559 <varname>Private=yes</varname> and has the effect that the
560 host side of the created virtual Ethernet link is connected to
561 the specified bridge interface. This option corresponds to the
562 <option>--network-bridge=</option> command line switch. This
563 option is privileged (see above).</para></listitem>
567 <term><varname>Zone=</varname></term>
569 <listitem><para>Takes a network zone name. This setting implies <varname>VirtualEthernet=yes</varname> and
570 <varname>Private=yes</varname> and has the effect that the host side of the created virtual Ethernet link is
571 connected to an automatically managed bridge interface named after the passed argument, prefixed with
572 <literal>vz-</literal>. This option corresponds to the <option>--network-zone=</option> command line
573 switch. This option is privileged (see above).</para></listitem>
577 <term><varname>Port=</varname></term>
579 <listitem><para>Exposes a TCP or UDP port of the container on
580 the host. This option corresponds to the
581 <option>--port=</option> command line switch, see
582 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
583 for the precise syntax of the argument this option takes. This
584 option is privileged (see above).</para></listitem>
590 <title>See Also</title>
592 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
593 <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
594 <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>