summaryrefslogtreecommitdiffstats
path: root/man/systemd-nspawn.xml
blob: aea50559f04f643e87ad6173390bc749f3a75663 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
        "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<!--
  This file is part of systemd.

  Copyright 2010 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->

<refentry id="systemd-nspawn"
          xmlns:xi="http://www.w3.org/2001/XInclude">

        <refentryinfo>
                <title>systemd-nspawn</title>
                <productname>systemd</productname>

                <authorgroup>
                        <author>
                                <contrib>Developer</contrib>
                                <firstname>Lennart</firstname>
                                <surname>Poettering</surname>
                                <email>lennart@poettering.net</email>
                        </author>
                </authorgroup>
        </refentryinfo>

        <refmeta>
                <refentrytitle>systemd-nspawn</refentrytitle>
                <manvolnum>1</manvolnum>
        </refmeta>

        <refnamediv>
                <refname>systemd-nspawn</refname>
                <refpurpose>Spawn a namespace container for debugging, testing and building</refpurpose>
        </refnamediv>

        <refsynopsisdiv>
                <cmdsynopsis>
                        <command>systemd-nspawn</command>
                        <arg choice="opt" rep="repeat">OPTIONS</arg>
                        <arg choice="opt"><replaceable>COMMAND</replaceable>
                        <arg choice="opt" rep="repeat">ARGS</arg>
                        </arg>
                </cmdsynopsis>
                <cmdsynopsis>
                        <command>systemd-nspawn</command>
                        <arg choice="plain">-b</arg>
                        <arg choice="opt" rep="repeat">OPTIONS</arg>
                        <arg choice="opt" rep="repeat">ARGS</arg>
                </cmdsynopsis>
        </refsynopsisdiv>

        <refsect1>
                <title>Description</title>

                <para><command>systemd-nspawn</command> may be used to
                run a command or OS in a light-weight namespace
                container. In many ways it is similar to
                <citerefentry project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                but more powerful since it fully virtualizes the file
                system hierarchy, as well as the process tree, the
                various IPC subsystems and the host and domain
                name.</para>

                <para><command>systemd-nspawn</command> limits access
                to various kernel interfaces in the container to
                read-only, such as <filename>/sys</filename>,
                <filename>/proc/sys</filename> or
                <filename>/sys/fs/selinux</filename>. Network
                interfaces and the system clock may not be changed
                from within the container. Device nodes may not be
                created. The host system cannot be rebooted and kernel
                modules may not be loaded from within the
                container.</para>

                <para>Note that even though these security precautions
                are taken <command>systemd-nspawn</command> is not
                suitable for secure container setups. Many of the
                security features may be circumvented and are hence
                primarily useful to avoid accidental changes to the
                host system from the container. The intended use of
                this program is debugging and testing as well as
                building of packages, distributions and software
                involved with boot and systems management.</para>

                <para>In contrast to
                <citerefentry project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry> <command>systemd-nspawn</command>
                may be used to boot full Linux-based operating systems
                in a container.</para>

                <para>Use a tool like
                <citerefentry project='die-net'><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
                <citerefentry project='die-net'><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
                or
                <citerefentry project='arch'><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>
                to set up an OS directory tree suitable as file system
                hierarchy for <command>systemd-nspawn</command>
                containers.</para>

                <para>Note that <command>systemd-nspawn</command> will
                mount file systems private to the container to
                <filename>/dev</filename>,
                <filename>/run</filename> and similar. These will
                not be visible outside of the container, and their
                contents will be lost when the container exits.</para>

                <para>Note that running two
                <command>systemd-nspawn</command> containers from the
                same directory tree will not make processes in them
                see each other. The PID namespace separation of the
                two containers is complete and the containers will
                share very few runtime objects except for the
                underlying file system. Use
                <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
                <command>login</command> command to request an
                additional login prompt in a running container.</para>

                <para><command>systemd-nspawn</command> implements the
                <ulink
                url="http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface">Container
                Interface</ulink> specification.</para>

                <para>As a safety check
                <command>systemd-nspawn</command> will verify the
                existence of <filename>/usr/lib/os-release</filename>
                or <filename>/etc/os-release</filename> in the
                container tree before starting the container (see
                <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>). It
                might be necessary to add this file to the container
                tree manually if the OS of the container is too old to
                contain this file out-of-the-box.</para>
        </refsect1>

        <refsect1>
                <title>Options</title>

                <para>If option <option>-b</option> is specified, the
                arguments are used as arguments for the init
                binary. Otherwise, <replaceable>COMMAND</replaceable>
                specifies the program to launch in the container, and
                the remaining arguments are used as arguments for this
                program. If <option>-b</option> is not used and no
                arguments are specifed, a shell is launched in the
                container.</para>

                <para>The following options are understood:</para>

                <variablelist>
                        <varlistentry>
                                <term><option>-D</option></term>
                                <term><option>--directory=</option></term>

                                <listitem><para>Directory to use as
                                file system root for the container. If
                                neither <option>--directory=</option>
                                nor <option>--image=</option> are
                                specified, the current directory will
                                be used. May not be specified together with
                                <option>--image=</option>.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>-i</option></term>
                                <term><option>--image=</option></term>

                                <listitem><para>Disk image to mount
                                the root directory for the container
                                from. Takes a path to a regular file
                                or to a block device node. The file or
                                block device must contain a GUID
                                Partition Table with a root partition
                                which is mounted as the root directory
                                of the container. Optionally, it may
                                contain a home and/or a server data
                                partition which are mounted to the
                                appropriate places in the
                                container. All these partitions must
                                be identified by the partition types
                                defined by the <ulink
                                url="http://www.freedesktop.org/wiki/Specifications/DiscoverablePartitionsSpec/">Discoverable
                                Partitions Specification</ulink>. Any
                                other partitions, such as foreign
                                partitions, swap partitions or EFI
                                system partitions are not mounted. May
                                not be specified together with
                                <option>--directory=</option>.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>-b</option></term>
                                <term><option>--boot</option></term>

                                <listitem><para>Automatically search
                                for an init binary and invoke it
                                instead of a shell or a user supplied
                                program. If this option is used,
                                arguments specified on the command
                                line are used as arguments for the
                                init binary. This option may not be
                                combined with
                                <option>--share-system</option>.
                                </para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>-u</option></term>
                                <term><option>--user=</option></term>

                                <listitem><para>After transitioning
                                into the container, change to the
                                specified user-defined in the
                                container's user database. Like all
                                other systemd-nspawn features, this is
                                not a security feature and provides
                                protection against accidental
                                destructive operations
                                only.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>-M</option></term>
                                <term><option>--machine=</option></term>

                                <listitem><para>Sets the machine name
                                for this container. This name may be
                                used to identify this container on the
                                host, and is used to initialize the
                                container's hostname (which the
                                container can choose to override,
                                however). If not specified, the last
                                component of the root directory of the
                                container is used.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--uuid=</option></term>

                                <listitem><para>Set the specified UUID
                                for the container. The init system
                                will initialize
                                <filename>/etc/machine-id</filename>
                                from this if this file is not set yet.
                                </para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--slice=</option></term>

                                <listitem><para>Make the container
                                part of the specified slice, instead
                                of the default
                                <filename>machine.slice</filename>.</para>
                                </listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--private-network</option></term>

                                <listitem><para>Disconnect networking
                                of the container from the host. This
                                makes all network interfaces
                                unavailable in the container, with the
                                exception of the loopback device and
                                those specified with
                                <option>--network-interface=</option>
                                and configured with
                                <option>--network-veth</option>. If
                                this option is specified, the
                                CAP_NET_ADMIN capability will be added
                                to the set of capabilities the
                                container retains. The latter may be
                                disabled by using
                                <option>--drop-capability=</option>.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--network-interface=</option></term>

                                <listitem><para>Assign the specified
                                network interface to the
                                container. This will remove the
                                specified interface from the calling
                                namespace and place it in the
                                container. When the container
                                terminates, it is moved back to the
                                host namespace. Note that
                                <option>--network-interface=</option>
                                implies
                                <option>--private-network</option>. This
                                option may be used more than once to
                                add multiple network interfaces to the
                                container.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--network-macvlan=</option></term>

                                <listitem><para>Create a
                                <literal>macvlan</literal> interface
                                of the specified Ethernet network
                                interface and add it to the
                                container. A
                                <literal>macvlan</literal> interface
                                is a virtual interface that adds a
                                second MAC address to an existing
                                physical Ethernet link. The interface
                                in the container will be named after
                                the interface on the host, prefixed
                                with <literal>mv-</literal>. Note that
                                <option>--network-macvlan=</option>
                                implies
                                <option>--private-network</option>. This
                                option may be used more than once to
                                add multiple network interfaces to the
                                container.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--network-veth</option></term>

                                <listitem><para>Create a virtual
                                Ethernet link
                                (<literal>veth</literal>) between host
                                and container. The host side of the
                                Ethernet link will be available as a
                                network interface named after the
                                container's name (as specified with
                                <option>--machine=</option>), prefixed
                                with <literal>ve-</literal>. The
                                container side of the Ethernet
                                link will be named
                                <literal>host0</literal>. Note that
                                <option>--network-veth</option>
                                implies
                                <option>--private-network</option>.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--network-bridge=</option></term>

                                <listitem><para>Adds the host side of
                                the Ethernet link created with
                                <option>--network-veth</option> to the
                                specified bridge. Note that
                                <option>--network-bridge=</option>
                                implies
                                <option>--network-veth</option>. If
                                this option is used, the host side of
                                the Ethernet link will use the
                                <literal>vb-</literal> prefix instead
                                of <literal>ve-</literal>.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>-Z</option></term>
                                <term><option>--selinux-context=</option></term>

                                <listitem><para>Sets the SELinux
                                security context to be used to label
                                processes in the container.</para>
                                </listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>-L</option></term>
                                <term><option>--selinux-apifs-context=</option></term>

                                <listitem><para>Sets the SELinux security
                                context to be used to label files in
                                the virtual API file systems in the
                                container.</para>
                                </listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--capability=</option></term>

                                <listitem><para>List one or more
                                additional capabilities to grant the
                                container. Takes a comma-separated
                                list of capability names, see
                                <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
                                for more information. Note that the
                                following capabilities will be granted
                                in any way: CAP_CHOWN,
                                CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH,
                                CAP_FOWNER, CAP_FSETID, CAP_IPC_OWNER,
                                CAP_KILL, CAP_LEASE,
                                CAP_LINUX_IMMUTABLE,
                                CAP_NET_BIND_SERVICE,
                                CAP_NET_BROADCAST, CAP_NET_RAW,
                                CAP_SETGID, CAP_SETFCAP, CAP_SETPCAP,
                                CAP_SETUID, CAP_SYS_ADMIN,
                                CAP_SYS_CHROOT, CAP_SYS_NICE,
                                CAP_SYS_PTRACE, CAP_SYS_TTY_CONFIG,
                                CAP_SYS_RESOURCE, CAP_SYS_BOOT,
                                CAP_AUDIT_WRITE,
                                CAP_AUDIT_CONTROL. Also CAP_NET_ADMIN
                                is retained if
                                <option>--private-network</option> is
                                specified. If the special value
                                <literal>all</literal> is passed, all
                                capabilities are
                                retained.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--drop-capability=</option></term>

                                <listitem><para>Specify one or more
                                additional capabilities to drop for
                                the container. This allows running the
                                container with fewer capabilities than
                                the default (see above).</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--link-journal=</option></term>

                                <listitem><para>Control whether the
                                container's journal shall be made
                                visible to the host system. If enabled,
                                allows viewing the container's journal
                                files from the host (but not vice
                                versa). Takes one of
                                <literal>no</literal>,
                                <literal>host</literal>,
                                <literal>guest</literal>,
                                <literal>auto</literal>. If
                                <literal>no</literal>, the journal is
                                not linked. If <literal>host</literal>,
                                the journal files are stored on the
                                host file system (beneath
                                <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
                                and the subdirectory is bind-mounted
                                into the container at the same
                                location. If <literal>guest</literal>,
                                the journal files are stored on the
                                guest file system (beneath
                                <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
                                and the subdirectory is symlinked into the host
                                at the same location. If
                                <literal>auto</literal> (the default),
                                and the right subdirectory of
                                <filename>/var/log/journal</filename>
                                exists, it will be bind mounted
                                into the container. If the
                                subdirectory does not exist, no
                                linking is performed. Effectively,
                                booting a container once with
                                <literal>guest</literal> or
                                <literal>host</literal> will link the
                                journal persistently if further on
                                the default of <literal>auto</literal>
                                is used.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>-j</option></term>

                                <listitem><para>Equivalent to
                                <option>--link-journal=guest</option>.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--read-only</option></term>

                                <listitem><para>Mount the root file
                                system read-only for the
                                container.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--bind=</option></term>
                                <term><option>--bind-ro=</option></term>

                                <listitem><para>Bind mount a file or
                                directory from the host into the
                                container. Either takes a path
                                argument -- in which case the
                                specified path will be mounted from
                                the host to the same path in the
                                container --, or a colon-separated
                                pair of paths -- in which case the
                                first specified path is the source in
                                the host, and the second path is the
                                destination in the container. The
                                <option>--bind-ro=</option> option
                                creates read-only bind
                                mounts.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--tmpfs=</option></term>

                                <listitem><para>Mount a tmpfs file
                                system into the container. Takes a
                                single absolute path argument that
                                specifies where to mount the tmpfs
                                instance to (in which case the
                                directory access mode will be chosen
                                as 0755, owned by root/root), or
                                optionally a colon-separated pair of
                                path and mount option string, that is
                                used for mounting (in which case the
                                kernel default for access mode and
                                owner will be chosen, unless otherwise
                                specified). This option is
                                particularly useful for mounting
                                directories such as
                                <filename>/var</filename> as tmpfs, to
                                allow state-less systems, in
                                particular when combined with
                                <option>--read-only</option>.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--setenv=</option></term>

                                <listitem><para>Specifies an
                                environment variable assignment to
                                pass to the init process in the
                                container, in the format
                                <literal>NAME=VALUE</literal>. This
                                may be used to override the default
                                variables or to set additional
                                variables. This parameter may be used
                                more than once.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--share-system</option></term>

                                <listitem><para>Allows the container
                                to share certain system facilities
                                with the host. More specifically, this
                                turns off PID namespacing, UTS
                                namespacing and IPC namespacing, and
                                thus allows the guest to see and
                                interact more easily with processes
                                outside of the container. Note that
                                using this option makes it impossible
                                to start up a full Operating System in
                                the container, as an init system
                                cannot operate in this mode. It is
                                only useful to run specific programs
                                or applications this way, without
                                involving an init system in the
                                container. This option implies
                                <option>--register=no</option>. This
                                option may not be combined with
                                <option>--boot</option>.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--register=</option></term>

                                <listitem><para>Controls whether the
                                container is registered with
                                <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>. Takes
                                a boolean argument, defaults to
                                <literal>yes</literal>. This option
                                should be enabled when the container
                                runs a full Operating System (more
                                specifically: an init system), and is
                                useful to ensure that the container is
                                accessible via
                                <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
                                and shown by tools such as
                                <citerefentry project='man-pages'><refentrytitle>ps</refentrytitle><manvolnum>1</manvolnum></citerefentry>. If
                                the container does not run an init
                                system, it is recommended to set this
                                option to <literal>no</literal>. Note
                                that <option>--share-system</option>
                                implies
                                <option>--register=no</option>.
                                </para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--keep-unit</option></term>

                                <listitem><para>Instead of creating a
                                transient scope unit to run the
                                container in, simply register the
                                service or scope unit
                                <command>systemd-nspawn</command> has
                                been invoked in with
                                <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>. This
                                has no effect if
                                <option>--register=no</option> is
                                used. This switch should be used if
                                <command>systemd-nspawn</command> is
                                invoked from within a service unit,
                                and the service unit's sole purpose
                                is to run a single
                                <command>systemd-nspawn</command>
                                container. This option is not
                                available if run from a user
                                session.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--personality=</option></term>

                                <listitem><para>Control the
                                architecture ("personality") reported
                                by
                                <citerefentry><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry>
                                in the container. Currently, only
                                <literal>x86</literal> and
                                <literal>x86-64</literal> are
                                supported. This is useful when running
                                a 32-bit container on a 64-bit
                                host. If this setting is not used,
                                the personality reported in the
                                container is the same as the one
                                reported on the
                                host.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>-q</option></term>
                                <term><option>--quiet</option></term>

                                <listitem><para>Turns off any status
                                output by the tool itself. When this
                                switch is used, the only output
                                from nspawn will be the console output
                                of the container OS itself.</para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--volatile</option><replaceable>=MODE</replaceable></term>

                                <listitem><para>Boots the container in
                                volatile (ephemeral) mode. When no
                                mode parameter is passed or when mode
                                is specified as <literal>yes</literal>
                                full volatile mode is enabled. This
                                means the root directory is mounted as
                                mostly unpopulated
                                <literal>tmpfs</literal> instance, and
                                <filename>/usr</filename> from the OS
                                tree is mounted into it, read-only
                                (the system thus starts up with
                                read-only OS resources, but pristine
                                state and configuration, any changes
                                to the either are lost on
                                shutdown). When the mode parameter is
                                specified as <literal>state</literal>
                                the OS tree is mounted read-only, but
                                <filename>/var</filename> is mounted
                                as <literal>tmpfs</literal> instance
                                into it (the system thus starts up
                                with read-only OS resources and
                                configuration, but prestine state, any
                                changes to the latter are lost on
                                shutdown). When the mode parameter is
                                specified as <literal>no</literal>
                                (the default) the whole OS tree is made
                                available writable.</para>

                                <para>Note that setting this to
                                <literal>yes</literal> or
                                <literal>state</literal> will only
                                work correctly with operating systems
                                in the container that can boot up with
                                only <filename>/usr</filename>
                                mounted, and are able to populate
                                <filename>/var</filename>
                                automatically, as
                                needed.</para></listitem>
                        </varlistentry>

                        <xi:include href="standard-options.xml" xpointer="help" />
                        <xi:include href="standard-options.xml" xpointer="version" />
                </variablelist>

        </refsect1>

        <refsect1>
                <title>Example 1</title>

                <programlisting># yum -y --releasever=19 --nogpg --installroot=/srv/mycontainer --disablerepo='*' --enablerepo=fedora install systemd passwd yum fedora-release vim-minimal
# systemd-nspawn -bD /srv/mycontainer</programlisting>

                <para>This installs a minimal Fedora distribution into
                the directory <filename noindex='true'>/srv/mycontainer/</filename> and
                then boots an OS in a namespace container in
                it.</para>
        </refsect1>

        <refsect1>
                <title>Example 2</title>

                <programlisting># debootstrap --arch=amd64 unstable ~/debian-tree/
# systemd-nspawn -D ~/debian-tree/</programlisting>

                <para>This installs a minimal Debian unstable
                distribution into the directory
                <filename>~/debian-tree/</filename> and then spawns a
                shell in a namespace container in it.</para>
        </refsect1>

        <refsect1>
                <title>Example 3</title>

                <programlisting># pacstrap -c -d ~/arch-tree/ base
# systemd-nspawn -bD ~/arch-tree/</programlisting>

                <para>This installs a mimimal Arch Linux distribution into
                the directory <filename>~/arch-tree/</filename> and then
                boots an OS in a namespace container in it.</para>
        </refsect1>

        <refsect1>
                <title>Example 4</title>

                <programlisting># mv ~/arch-tree /var/lib/container/arch
# systemctl enable systemd-nspawn@arch.service
# systemctl start systemd-nspawn@arch.service</programlisting>

                <para>This makes the Arch Linux container part of the
                <filename>multi-user.target</filename> on the host.
                </para>
        </refsect1>

        <refsect1>
                <title>Example 5</title>

                <programlisting># btrfs subvolume snapshot / /.tmp
# systemd-nspawn --private-network -D /.tmp -b</programlisting>

                <para>This runs a copy of the host system in a
                btrfs snapshot.</para>
        </refsect1>

        <refsect1>
                <title>Example 6</title>

                <programlisting># chcon system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -R /srv/container
# systemd-nspawn -L system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -Z system_u:system_r:svirt_lxc_net_t:s0:c0,c1 -D /srv/container /bin/sh</programlisting>

                <para>This runs a container with SELinux sandbox security contexts.</para>
        </refsect1>

        <refsect1>
                <title>Exit status</title>

                <para>The exit code of the program executed in the
                container is returned.</para>
        </refsect1>

        <refsect1>
                <title>See Also</title>
                <para>
                        <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                        <citerefentry project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                        <citerefentry project='die-net'><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
                        <citerefentry project='die-net'><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
                        <citerefentry project='arch'><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
                </para>
        </refsect1>

</refentry>