man/systemd-nspawn.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   This file is part of systemd.
   7
   8   Copyright 2010 Lennart Poettering
   9
  10   systemd is free software; you can redistribute it and/or modify it
  11   under the terms of the GNU Lesser General Public License as published by
  12   the Free Software Foundation; either version 2.1 of the License, or
  13   (at your option) any later version.
  14
  15   systemd is distributed in the hope that it will be useful, but
  16   WITHOUT ANY WARRANTY; without even the implied warranty of
  17   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  18   Lesser General Public License for more details.
  19
  20   You should have received a copy of the GNU Lesser General Public License
  21   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  22 -->
  23
  24 <refentry id="systemd-nspawn"
  25           xmlns:xi="http://www.w3.org/2001/XInclude">
  26
  27         <refentryinfo>
  28                 <title>systemd-nspawn</title>
  29                 <productname>systemd</productname>
  30
  31                 <authorgroup>
  32                         <author>
  33                                 <contrib>Developer</contrib>
  34                                 <firstname>Lennart</firstname>
  35                                 <surname>Poettering</surname>
  36                                 <email>lennart@poettering.net</email>
  37                         </author>
  38                 </authorgroup>
  39         </refentryinfo>
  40
  41         <refmeta>
  42                 <refentrytitle>systemd-nspawn</refentrytitle>
  43                 <manvolnum>1</manvolnum>
  44         </refmeta>
  45
  46         <refnamediv>
  47                 <refname>systemd-nspawn</refname>
  48                 <refpurpose>Spawn a namespace container for debugging, testing and building</refpurpose>
  49         </refnamediv>
  50
  51         <refsynopsisdiv>
  52                 <cmdsynopsis>
  53                         <command>systemd-nspawn</command>
  54                         <arg choice="opt" rep="repeat">OPTIONS</arg>
  55                         <arg choice="opt"><replaceable>COMMAND</replaceable>
  56                         <arg choice="opt" rep="repeat">ARGS</arg>
  57                         </arg>
  58                 </cmdsynopsis>
  59                 <cmdsynopsis>
  60                         <command>systemd-nspawn</command>
  61                         <arg choice="plain">-b</arg>
  62                         <arg choice="opt" rep="repeat">OPTIONS</arg>
  63                         <arg choice="opt" rep="repeat">ARGS</arg>
  64                 </cmdsynopsis>
  65         </refsynopsisdiv>
  66
  67         <refsect1>
  68                 <title>Description</title>
  69
  70                 <para><command>systemd-nspawn</command> may be used to
  71                 run a command or OS in a light-weight namespace
  72                 container. In many ways it is similar to
  73                 <citerefentry project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
  74                 but more powerful since it fully virtualizes the file
  75                 system hierarchy, as well as the process tree, the
  76                 various IPC subsystems and the host and domain
  77                 name.</para>
  78
  79                 <para><command>systemd-nspawn</command> limits access
  80                 to various kernel interfaces in the container to
  81                 read-only, such as <filename>/sys</filename>,
  82                 <filename>/proc/sys</filename> or
  83                 <filename>/sys/fs/selinux</filename>. Network
  84                 interfaces and the system clock may not be changed
  85                 from within the container. Device nodes may not be
  86                 created. The host system cannot be rebooted and kernel
  87                 modules may not be loaded from within the
  88                 container.</para>
  89
  90                 <para>Note that even though these security precautions
  91                 are taken <command>systemd-nspawn</command> is not
  92                 suitable for secure container setups. Many of the
  93                 security features may be circumvented and are hence
  94                 primarily useful to avoid accidental changes to the
  95                 host system from the container. The intended use of
  96                 this program is debugging and testing as well as
  97                 building of packages, distributions and software
  98                 involved with boot and systems management.</para>
  99
 100                 <para>In contrast to
 101                 <citerefentry project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry> <command>systemd-nspawn</command>
 102                 may be used to boot full Linux-based operating systems
 103                 in a container.</para>
 104
 105                 <para>Use a tool like
 106                 <citerefentry project='die-net'><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 107                 <citerefentry project='die-net'><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 108                 or
 109                 <citerefentry project='archlinux'><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 110                 to set up an OS directory tree suitable as file system
 111                 hierarchy for <command>systemd-nspawn</command>
 112                 containers.</para>
 113
 114                 <para>Note that <command>systemd-nspawn</command> will
 115                 mount file systems private to the container to
 116                 <filename>/dev</filename>,
 117                 <filename>/run</filename> and similar. These will
 118                 not be visible outside of the container, and their
 119                 contents will be lost when the container exits.</para>
 120
 121                 <para>Note that running two
 122                 <command>systemd-nspawn</command> containers from the
 123                 same directory tree will not make processes in them
 124                 see each other. The PID namespace separation of the
 125                 two containers is complete and the containers will
 126                 share very few runtime objects except for the
 127                 underlying file system. Use
 128                 <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
 129                 <command>login</command> command to request an
 130                 additional login prompt in a running container.</para>
 131
 132                 <para><command>systemd-nspawn</command> implements the
 133                 <ulink
 134                 url="http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface">Container
 135                 Interface</ulink> specification.</para>
 136
 137                 <para>As a safety check
 138                 <command>systemd-nspawn</command> will verify the
 139                 existence of <filename>/usr/lib/os-release</filename>
 140                 or <filename>/etc/os-release</filename> in the
 141                 container tree before starting the container (see
 142                 <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>). It
 143                 might be necessary to add this file to the container
 144                 tree manually if the OS of the container is too old to
 145                 contain this file out-of-the-box.</para>
 146         </refsect1>
 147
 148         <refsect1>
 149                 <title>Options</title>
 150
 151                 <para>If option <option>-b</option> is specified, the
 152                 arguments are used as arguments for the init
 153                 binary. Otherwise, <replaceable>COMMAND</replaceable>
 154                 specifies the program to launch in the container, and
 155                 the remaining arguments are used as arguments for this
 156                 program. If <option>-b</option> is not used and no
 157                 arguments are specifed, a shell is launched in the
 158                 container.</para>
 159
 160                 <para>The following options are understood:</para>
 161
 162                 <variablelist>
 163                         <varlistentry>
 164                                 <term><option>-D</option></term>
 165                                 <term><option>--directory=</option></term>
 166
 167                                 <listitem><para>Directory to use as
 168                                 file system root for the container.</para>
 169
 170                                 <para>If neither
 171                                 <option>--directory=</option>, nor
 172                                 <option>--image=</option> is specified
 173                                 the directory is determined as
 174                                 <filename>/var/lib/container/</filename>
 175                                 suffixed by the machine name as
 176                                 specified with
 177                                 <option>--machine=</option>. If
 178                                 neither <option>--directory=</option>,
 179                                 <option>--image=</option>, nor
 180                                 <option>--machine=</option> are
 181                                 specified, the current directory will
 182                                 be used. May not be specified together
 183                                 with
 184                                 <option>--image=</option>.</para></listitem>
 185                         </varlistentry>
 186
 187                         <varlistentry>
 188                                 <term><option>--template=</option></term>
 189
 190                                 <listitem><para>Directory or
 191                                 <literal>btrfs</literal> subvolume to
 192                                 use as template for the container's
 193                                 root directory. If this is specified
 194                                 and the container's root directory (as
 195                                 configured by
 196                                 <option>--directory=</option>) does
 197                                 not yet exist it is created as
 198                                 <literal>btrfs</literal> subvolume and
 199                                 populated from this template
 200                                 tree. Ideally, the specified template
 201                                 path refers to the root of a
 202                                 <literal>btrfs</literal> subvolume, in
 203                                 which case a simple copy-on-write
 204                                 snapshot is taken, and populating the
 205                                 root directory is instant. If the
 206                                 specified template path does not refer
 207                                 to the root of a
 208                                 <literal>btrfs</literal> subvolume (or
 209                                 not even to a <literal>btrfs</literal>
 210                                 file system at all), the tree is
 211                                 copied, which can be substantially
 212                                 more time-consuming. Note that if this
 213                                 option is used the container's root
 214                                 directory (in contrast to the template
 215                                 directory!) must be located on a
 216                                 <literal>btrfs</literal> file system,
 217                                 so that the <literal>btrfs</literal>
 218                                 subvolume may be created. May not be
 219                                 specified together with
 220                                 <option>--image=</option> or
 221                                 <option>--ephemeral</option>.</para></listitem>
 222                         </varlistentry>
 223
 224                         <varlistentry>
 225                                 <term><option>-x</option></term>
 226                                 <term><option>--ephemeral</option></term>
 227
 228                                 <listitem><para>If specified, the
 229                                 container is run with a temporary
 230                                 <literal>btrfs</literal> snapshot of
 231                                 its root directory (as configured with
 232                                 <option>--directory=</option>), that
 233                                 is removed immediately when the
 234                                 container terminates. This option is
 235                                 only supported if the root file system
 236                                 is <literal>btrfs</literal>. May not
 237                                 be specified together with
 238                                 <option>--image=</option> or
 239                                 <option>--template=</option>.</para></listitem>
 240                         </varlistentry>
 241
 242                         <varlistentry>
 243                                 <term><option>-i</option></term>
 244                                 <term><option>--image=</option></term>
 245
 246                                 <listitem><para>Disk image to mount
 247                                 the root directory for the container
 248                                 from. Takes a path to a regular file
 249                                 or to a block device node. The file or
 250                                 block device must contain a GUID
 251                                 Partition Table with a root partition
 252                                 which is mounted as the root directory
 253                                 of the container. Optionally, it may
 254                                 contain a home and/or a server data
 255                                 partition which are mounted to the
 256                                 appropriate places in the
 257                                 container. All these partitions must
 258                                 be identified by the partition types
 259                                 defined by the <ulink
 260                                 url="http://www.freedesktop.org/wiki/Specifications/DiscoverablePartitionsSpec/">Discoverable
 261                                 Partitions Specification</ulink>. Any
 262                                 other partitions, such as foreign
 263                                 partitions, swap partitions or EFI
 264                                 system partitions are not mounted. May
 265                                 not be specified together with
 266                                 <option>--directory=</option>,
 267                                 <option>--template=</option> or
 268                                 <option>--ephemeral</option>.</para></listitem>
 269                         </varlistentry>
 270
 271                         <varlistentry>
 272                                 <term><option>-b</option></term>
 273                                 <term><option>--boot</option></term>
 274
 275                                 <listitem><para>Automatically search
 276                                 for an init binary and invoke it
 277                                 instead of a shell or a user supplied
 278                                 program. If this option is used,
 279                                 arguments specified on the command
 280                                 line are used as arguments for the
 281                                 init binary. This option may not be
 282                                 combined with
 283                                 <option>--share-system</option>.
 284                                 </para></listitem>
 285                         </varlistentry>
 286
 287                         <varlistentry>
 288                                 <term><option>-u</option></term>
 289                                 <term><option>--user=</option></term>
 290
 291                                 <listitem><para>After transitioning
 292                                 into the container, change to the
 293                                 specified user-defined in the
 294                                 container's user database. Like all
 295                                 other systemd-nspawn features, this is
 296                                 not a security feature and provides
 297                                 protection against accidental
 298                                 destructive operations
 299                                 only.</para></listitem>
 300                         </varlistentry>
 301
 302                         <varlistentry>
 303                                 <term><option>-M</option></term>
 304                                 <term><option>--machine=</option></term>
 305
 306                                 <listitem><para>Sets the machine name
 307                                 for this container. This name may be
 308                                 used to identify this container during
 309                                 its runtime (for example in tools like
 310                                 <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 311                                 and similar), and is used to
 312                                 initialize the container's hostname
 313                                 (which the container can choose to
 314                                 override, however). If not specified,
 315                                 the last component of the root
 316                                 directory path of the container is
 317                                 used, possibly suffixed with a random
 318                                 identifier in case
 319                                 <option>--ephemeral</option> mode is
 320                                 selected. If the root directory
 321                                 selected is the host's root directory
 322                                 the host's hostname is used as default
 323                                 instead.</para></listitem>
 324                         </varlistentry>
 325
 326                         <varlistentry>
 327                                 <term><option>--uuid=</option></term>
 328
 329                                 <listitem><para>Set the specified UUID
 330                                 for the container. The init system
 331                                 will initialize
 332                                 <filename>/etc/machine-id</filename>
 333                                 from this if this file is not set yet.
 334                                 </para></listitem>
 335                         </varlistentry>
 336
 337                         <varlistentry>
 338                                 <term><option>--slice=</option></term>
 339
 340                                 <listitem><para>Make the container
 341                                 part of the specified slice, instead
 342                                 of the default
 343                                 <filename>machine.slice</filename>.</para>
 344                                 </listitem>
 345                         </varlistentry>
 346
 347                         <varlistentry>
 348                                 <term><option>--private-network</option></term>
 349
 350                                 <listitem><para>Disconnect networking
 351                                 of the container from the host. This
 352                                 makes all network interfaces
 353                                 unavailable in the container, with the
 354                                 exception of the loopback device and
 355                                 those specified with
 356                                 <option>--network-interface=</option>
 357                                 and configured with
 358                                 <option>--network-veth</option>. If
 359                                 this option is specified, the
 360                                 CAP_NET_ADMIN capability will be added
 361                                 to the set of capabilities the
 362                                 container retains. The latter may be
 363                                 disabled by using
 364                                 <option>--drop-capability=</option>.</para></listitem>
 365                         </varlistentry>
 366
 367                         <varlistentry>
 368                                 <term><option>--network-interface=</option></term>
 369
 370                                 <listitem><para>Assign the specified
 371                                 network interface to the
 372                                 container. This will remove the
 373                                 specified interface from the calling
 374                                 namespace and place it in the
 375                                 container. When the container
 376                                 terminates, it is moved back to the
 377                                 host namespace. Note that
 378                                 <option>--network-interface=</option>
 379                                 implies
 380                                 <option>--private-network</option>. This
 381                                 option may be used more than once to
 382                                 add multiple network interfaces to the
 383                                 container.</para></listitem>
 384                         </varlistentry>
 385
 386                         <varlistentry>
 387                                 <term><option>--network-macvlan=</option></term>
 388
 389                                 <listitem><para>Create a
 390                                 <literal>macvlan</literal> interface
 391                                 of the specified Ethernet network
 392                                 interface and add it to the
 393                                 container. A
 394                                 <literal>macvlan</literal> interface
 395                                 is a virtual interface that adds a
 396                                 second MAC address to an existing
 397                                 physical Ethernet link. The interface
 398                                 in the container will be named after
 399                                 the interface on the host, prefixed
 400                                 with <literal>mv-</literal>. Note that
 401                                 <option>--network-macvlan=</option>
 402                                 implies
 403                                 <option>--private-network</option>. This
 404                                 option may be used more than once to
 405                                 add multiple network interfaces to the
 406                                 container.</para></listitem>
 407                         </varlistentry>
 408
 409                         <varlistentry>
 410                                 <term><option>--network-veth</option></term>
 411
 412                                 <listitem><para>Create a virtual
 413                                 Ethernet link
 414                                 (<literal>veth</literal>) between host
 415                                 and container. The host side of the
 416                                 Ethernet link will be available as a
 417                                 network interface named after the
 418                                 container's name (as specified with
 419                                 <option>--machine=</option>), prefixed
 420                                 with <literal>ve-</literal>. The
 421                                 container side of the Ethernet
 422                                 link will be named
 423                                 <literal>host0</literal>. Note that
 424                                 <option>--network-veth</option>
 425                                 implies
 426                                 <option>--private-network</option>.</para></listitem>
 427                         </varlistentry>
 428
 429                         <varlistentry>
 430                                 <term><option>--network-bridge=</option></term>
 431
 432                                 <listitem><para>Adds the host side of
 433                                 the Ethernet link created with
 434                                 <option>--network-veth</option> to the
 435                                 specified bridge. Note that
 436                                 <option>--network-bridge=</option>
 437                                 implies
 438                                 <option>--network-veth</option>. If
 439                                 this option is used, the host side of
 440                                 the Ethernet link will use the
 441                                 <literal>vb-</literal> prefix instead
 442                                 of <literal>ve-</literal>.</para></listitem>
 443                         </varlistentry>
 444
 445                         <varlistentry>
 446                                 <term><option>-Z</option></term>
 447                                 <term><option>--selinux-context=</option></term>
 448
 449                                 <listitem><para>Sets the SELinux
 450                                 security context to be used to label
 451                                 processes in the container.</para>
 452                                 </listitem>
 453                         </varlistentry>
 454
 455                         <varlistentry>
 456                                 <term><option>-L</option></term>
 457                                 <term><option>--selinux-apifs-context=</option></term>
 458
 459                                 <listitem><para>Sets the SELinux security
 460                                 context to be used to label files in
 461                                 the virtual API file systems in the
 462                                 container.</para>
 463                                 </listitem>
 464                         </varlistentry>
 465
 466                         <varlistentry>
 467                                 <term><option>--capability=</option></term>
 468
 469                                 <listitem><para>List one or more
 470                                 additional capabilities to grant the
 471                                 container. Takes a comma-separated
 472                                 list of capability names, see
 473                                 <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 474                                 for more information. Note that the
 475                                 following capabilities will be granted
 476                                 in any way: CAP_CHOWN,
 477                                 CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH,
 478                                 CAP_FOWNER, CAP_FSETID, CAP_IPC_OWNER,
 479                                 CAP_KILL, CAP_LEASE,
 480                                 CAP_LINUX_IMMUTABLE,
 481                                 CAP_NET_BIND_SERVICE,
 482                                 CAP_NET_BROADCAST, CAP_NET_RAW,
 483                                 CAP_SETGID, CAP_SETFCAP, CAP_SETPCAP,
 484                                 CAP_SETUID, CAP_SYS_ADMIN,
 485                                 CAP_SYS_CHROOT, CAP_SYS_NICE,
 486                                 CAP_SYS_PTRACE, CAP_SYS_TTY_CONFIG,
 487                                 CAP_SYS_RESOURCE, CAP_SYS_BOOT,
 488                                 CAP_AUDIT_WRITE,
 489                                 CAP_AUDIT_CONTROL. Also CAP_NET_ADMIN
 490                                 is retained if
 491                                 <option>--private-network</option> is
 492                                 specified. If the special value
 493                                 <literal>all</literal> is passed, all
 494                                 capabilities are
 495                                 retained.</para></listitem>
 496                         </varlistentry>
 497
 498                         <varlistentry>
 499                                 <term><option>--drop-capability=</option></term>
 500
 501                                 <listitem><para>Specify one or more
 502                                 additional capabilities to drop for
 503                                 the container. This allows running the
 504                                 container with fewer capabilities than
 505                                 the default (see above).</para></listitem>
 506                         </varlistentry>
 507
 508                         <varlistentry>
 509                                 <term><option>--link-journal=</option></term>
 510
 511                                 <listitem><para>Control whether the
 512                                 container's journal shall be made
 513                                 visible to the host system. If enabled,
 514                                 allows viewing the container's journal
 515                                 files from the host (but not vice
 516                                 versa). Takes one of
 517                                 <literal>no</literal>,
 518                                 <literal>host</literal>,
 519                                 <literal>try-host</literal>,
 520                                 <literal>guest</literal>,
 521                                 <literal>try-guest</literal>,
 522                                 <literal>auto</literal>. If
 523                                 <literal>no</literal>, the journal is
 524                                 not linked. If <literal>host</literal>,
 525                                 the journal files are stored on the
 526                                 host file system (beneath
 527                                 <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
 528                                 and the subdirectory is bind-mounted
 529                                 into the container at the same
 530                                 location. If <literal>guest</literal>,
 531                                 the journal files are stored on the
 532                                 guest file system (beneath
 533                                 <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
 534                                 and the subdirectory is symlinked into the host
 535                                 at the same location. <literal>try-host</literal>
 536                                 and <literal>try-guest</literal> do the same
 537                                 but do not fail if the host does not have
 538                                 persistent journalling enabled.
 539                                 If <literal>auto</literal> (the default),
 540                                 and the right subdirectory of
 541                                 <filename>/var/log/journal</filename>
 542                                 exists, it will be bind mounted
 543                                 into the container. If the
 544                                 subdirectory does not exist, no
 545                                 linking is performed. Effectively,
 546                                 booting a container once with
 547                                 <literal>guest</literal> or
 548                                 <literal>host</literal> will link the
 549                                 journal persistently if further on
 550                                 the default of <literal>auto</literal>
 551                                 is used.</para></listitem>
 552                         </varlistentry>
 553
 554                         <varlistentry>
 555                                 <term><option>-j</option></term>
 556
 557                                 <listitem><para>Equivalent to
 558                                 <option>--link-journal=try-guest</option>.</para></listitem>
 559                         </varlistentry>
 560
 561                         <varlistentry>
 562                                 <term><option>--read-only</option></term>
 563
 564                                 <listitem><para>Mount the root file
 565                                 system read-only for the
 566                                 container.</para></listitem>
 567                         </varlistentry>
 568
 569                         <varlistentry>
 570                                 <term><option>--bind=</option></term>
 571                                 <term><option>--bind-ro=</option></term>
 572
 573                                 <listitem><para>Bind mount a file or
 574                                 directory from the host into the
 575                                 container. Either takes a path
 576                                 argument -- in which case the
 577                                 specified path will be mounted from
 578                                 the host to the same path in the
 579                                 container --, or a colon-separated
 580                                 pair of paths -- in which case the
 581                                 first specified path is the source in
 582                                 the host, and the second path is the
 583                                 destination in the container. The
 584                                 <option>--bind-ro=</option> option
 585                                 creates read-only bind
 586                                 mounts.</para></listitem>
 587                         </varlistentry>
 588
 589                         <varlistentry>
 590                                 <term><option>--tmpfs=</option></term>
 591
 592                                 <listitem><para>Mount a tmpfs file
 593                                 system into the container. Takes a
 594                                 single absolute path argument that
 595                                 specifies where to mount the tmpfs
 596                                 instance to (in which case the
 597                                 directory access mode will be chosen
 598                                 as 0755, owned by root/root), or
 599                                 optionally a colon-separated pair of
 600                                 path and mount option string, that is
 601                                 used for mounting (in which case the
 602                                 kernel default for access mode and
 603                                 owner will be chosen, unless otherwise
 604                                 specified). This option is
 605                                 particularly useful for mounting
 606                                 directories such as
 607                                 <filename>/var</filename> as tmpfs, to
 608                                 allow state-less systems, in
 609                                 particular when combined with
 610                                 <option>--read-only</option>.</para></listitem>
 611                         </varlistentry>
 612
 613                         <varlistentry>
 614                                 <term><option>--setenv=</option></term>
 615
 616                                 <listitem><para>Specifies an
 617                                 environment variable assignment to
 618                                 pass to the init process in the
 619                                 container, in the format
 620                                 <literal>NAME=VALUE</literal>. This
 621                                 may be used to override the default
 622                                 variables or to set additional
 623                                 variables. This parameter may be used
 624                                 more than once.</para></listitem>
 625                         </varlistentry>
 626
 627                         <varlistentry>
 628                                 <term><option>--share-system</option></term>
 629
 630                                 <listitem><para>Allows the container
 631                                 to share certain system facilities
 632                                 with the host. More specifically, this
 633                                 turns off PID namespacing, UTS
 634                                 namespacing and IPC namespacing, and
 635                                 thus allows the guest to see and
 636                                 interact more easily with processes
 637                                 outside of the container. Note that
 638                                 using this option makes it impossible
 639                                 to start up a full Operating System in
 640                                 the container, as an init system
 641                                 cannot operate in this mode. It is
 642                                 only useful to run specific programs
 643                                 or applications this way, without
 644                                 involving an init system in the
 645                                 container. This option implies
 646                                 <option>--register=no</option>. This
 647                                 option may not be combined with
 648                                 <option>--boot</option>.</para></listitem>
 649                         </varlistentry>
 650
 651                         <varlistentry>
 652                                 <term><option>--register=</option></term>
 653
 654                                 <listitem><para>Controls whether the
 655                                 container is registered with
 656                                 <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>. Takes
 657                                 a boolean argument, defaults to
 658                                 <literal>yes</literal>. This option
 659                                 should be enabled when the container
 660                                 runs a full Operating System (more
 661                                 specifically: an init system), and is
 662                                 useful to ensure that the container is
 663                                 accessible via
 664                                 <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 665                                 and shown by tools such as
 666                                 <citerefentry project='man-pages'><refentrytitle>ps</refentrytitle><manvolnum>1</manvolnum></citerefentry>. If
 667                                 the container does not run an init
 668                                 system, it is recommended to set this
 669                                 option to <literal>no</literal>. Note
 670                                 that <option>--share-system</option>
 671                                 implies
 672                                 <option>--register=no</option>.
 673                                 </para></listitem>
 674                         </varlistentry>
 675
 676                         <varlistentry>
 677                                 <term><option>--keep-unit</option></term>
 678
 679                                 <listitem><para>Instead of creating a
 680                                 transient scope unit to run the
 681                                 container in, simply register the
 682                                 service or scope unit
 683                                 <command>systemd-nspawn</command> has
 684                                 been invoked in with
 685                                 <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>. This
 686                                 has no effect if
 687                                 <option>--register=no</option> is
 688                                 used. This switch should be used if
 689                                 <command>systemd-nspawn</command> is
 690                                 invoked from within a service unit,
 691                                 and the service unit's sole purpose
 692                                 is to run a single
 693                                 <command>systemd-nspawn</command>
 694                                 container. This option is not
 695                                 available if run from a user
 696                                 session.</para></listitem>
 697                         </varlistentry>
 698
 699                         <varlistentry>
 700                                 <term><option>--personality=</option></term>
 701
 702                                 <listitem><para>Control the
 703                                 architecture ("personality") reported
 704                                 by
 705                                 <citerefentry><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 706                                 in the container. Currently, only
 707                                 <literal>x86</literal> and
 708                                 <literal>x86-64</literal> are
 709                                 supported. This is useful when running
 710                                 a 32-bit container on a 64-bit
 711                                 host. If this setting is not used,
 712                                 the personality reported in the
 713                                 container is the same as the one
 714                                 reported on the
 715                                 host.</para></listitem>
 716                         </varlistentry>
 717
 718                         <varlistentry>
 719                                 <term><option>-q</option></term>
 720                                 <term><option>--quiet</option></term>
 721
 722                                 <listitem><para>Turns off any status
 723                                 output by the tool itself. When this
 724                                 switch is used, the only output
 725                                 from nspawn will be the console output
 726                                 of the container OS itself.</para></listitem>
 727                         </varlistentry>
 728
 729                         <varlistentry>
 730                                 <term><option>--volatile</option><replaceable>=MODE</replaceable></term>
 731
 732                                 <listitem><para>Boots the container in
 733                                 volatile mode. When no mode parameter
 734                                 is passed or when mode is specified as
 735                                 <literal>yes</literal> full volatile
 736                                 mode is enabled. This means the root
 737                                 directory is mounted as mostly
 738                                 unpopulated <literal>tmpfs</literal>
 739                                 instance, and
 740                                 <filename>/usr</filename> from the OS
 741                                 tree is mounted into it, read-only
 742                                 (the system thus starts up with
 743                                 read-only OS resources, but pristine
 744                                 state and configuration, any changes
 745                                 to the either are lost on
 746                                 shutdown). When the mode parameter is
 747                                 specified as <literal>state</literal>
 748                                 the OS tree is mounted read-only, but
 749                                 <filename>/var</filename> is mounted
 750                                 as <literal>tmpfs</literal> instance
 751                                 into it (the system thus starts up
 752                                 with read-only OS resources and
 753                                 configuration, but pristine state, any
 754                                 changes to the latter are lost on
 755                                 shutdown). When the mode parameter is
 756                                 specified as <literal>no</literal>
 757                                 (the default) the whole OS tree is
 758                                 made available writable.</para>
 759
 760                                 <para>Note that setting this to
 761                                 <literal>yes</literal> or
 762                                 <literal>state</literal> will only
 763                                 work correctly with operating systems
 764                                 in the container that can boot up with
 765                                 only <filename>/usr</filename>
 766                                 mounted, and are able to populate
 767                                 <filename>/var</filename>
 768                                 automatically, as
 769                                 needed.</para></listitem>
 770                         </varlistentry>
 771
 772                         <xi:include href="standard-options.xml" xpointer="help" />
 773                         <xi:include href="standard-options.xml" xpointer="version" />
 774                 </variablelist>
 775
 776         </refsect1>
 777
 778         <refsect1>
 779                 <title>Examples</title>
 780                 <example>
 781                         <title>Boot a minimal Fedora distribution in a container</title>
 782
 783                         <programlisting># yum -y --releasever=21 --nogpg --installroot=/srv/mycontainer --disablerepo='*' --enablerepo=fedora install systemd passwd yum fedora-release vim-minimal
 784 # systemd-nspawn -bD /srv/mycontainer</programlisting>
 785
 786                         <para>This installs a minimal Fedora distribution into
 787                         the directory <filename noindex='true'>/srv/mycontainer/</filename> and
 788                         then boots an OS in a namespace container in
 789                         it.</para>
 790                 </example>
 791
 792                 <example>
 793                         <title>Spawn a shell in a container of a minimal Debian unstable distribution</title>
 794
 795                         <programlisting># debootstrap --arch=amd64 unstable ~/debian-tree/
 796 # systemd-nspawn -D ~/debian-tree/</programlisting>
 797
 798                         <para>This installs a minimal Debian unstable
 799                         distribution into the directory
 800                         <filename>~/debian-tree/</filename> and then spawns a
 801                         shell in a namespace container in it.</para>
 802                 </example>
 803
 804                 <example>
 805                         <title>Boot a minimal Arch Linux distribution in a container</title>
 806
 807                         <programlisting># pacstrap -c -d ~/arch-tree/ base
 808 # systemd-nspawn -bD ~/arch-tree/</programlisting>
 809
 810                         <para>This installs a mimimal Arch Linux distribution into
 811                         the directory <filename>~/arch-tree/</filename> and then
 812                         boots an OS in a namespace container in it.</para>
 813                 </example>
 814
 815                 <example>
 816                         <title>Enable Arch Linux container on boot</title>
 817
 818                         <programlisting># mv ~/arch-tree /var/lib/container/arch
 819 # systemctl enable systemd-nspawn@arch.service
 820 # systemctl start systemd-nspawn@arch.service</programlisting>
 821
 822                         <para>This makes the Arch Linux container part of the
 823                         <filename>multi-user.target</filename> on the host.
 824                         </para>
 825                 </example>
 826
 827                 <example>
 828                         <title>Boot into an ephemeral <literal>btrfs</literal> snapshot of the host system</title>
 829
 830                         <programlisting># systemd-nspawn -D / -xb</programlisting>
 831
 832                         <para>This runs a copy of the host system in a
 833                         <literal>btrfs</literal> snapshot which is
 834                         removed immediately when the container
 835                         exits. All file system changes made during
 836                         runtime will be lost on shutdown,
 837                         hence.</para>
 838                 </example>
 839
 840                 <example>
 841                         <title>Run a container with SELinux sandbox security contexts</title>
 842
 843                         <programlisting># chcon system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -R /srv/container
 844 # 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>
 845                 </example>
 846         </refsect1>
 847
 848         <refsect1>
 849                 <title>Exit status</title>
 850
 851                 <para>The exit code of the program executed in the
 852                 container is returned.</para>
 853         </refsect1>
 854
 855         <refsect1>
 856                 <title>See Also</title>
 857                 <para>
 858                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 859                         <citerefentry project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 860                         <citerefentry project='die-net'><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 861                         <citerefentry project='die-net'><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 862                         <citerefentry project='archlinux'><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 863                         <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 864                         <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 865                         <citerefentry><refentrytitle>btrfs</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 866                 </para>
 867         </refsect1>
 868
 869 </refentry>