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>-n</option></term>
 411                                 <term><option>--network-veth</option></term>
 412
 413                                 <listitem><para>Create a virtual
 414                                 Ethernet link
 415                                 (<literal>veth</literal>) between host
 416                                 and container. The host side of the
 417                                 Ethernet link will be available as a
 418                                 network interface named after the
 419                                 container's name (as specified with
 420                                 <option>--machine=</option>), prefixed
 421                                 with <literal>ve-</literal>. The
 422                                 container side of the Ethernet
 423                                 link will be named
 424                                 <literal>host0</literal>. Note that
 425                                 <option>--network-veth</option>
 426                                 implies
 427                                 <option>--private-network</option>.</para></listitem>
 428                         </varlistentry>
 429
 430                         <varlistentry>
 431                                 <term><option>--network-bridge=</option></term>
 432
 433                                 <listitem><para>Adds the host side of
 434                                 the Ethernet link created with
 435                                 <option>--network-veth</option> to the
 436                                 specified bridge. Note that
 437                                 <option>--network-bridge=</option>
 438                                 implies
 439                                 <option>--network-veth</option>. If
 440                                 this option is used, the host side of
 441                                 the Ethernet link will use the
 442                                 <literal>vb-</literal> prefix instead
 443                                 of <literal>ve-</literal>.</para></listitem>
 444                         </varlistentry>
 445
 446                         <varlistentry>
 447                                 <term><option>-p</option></term>
 448                                 <term><option>--port=</option></term>
 449
 450                                 <listitem><para>If private networking
 451                                 is enabled, maps an IP port on the
 452                                 host onto an IP port on the
 453                                 container. Takes a protocol specifier
 454                                 (either <literal>tcp</literal> or
 455                                 <literal>udp</literal>), separated by
 456                                 a colon from a host port number in the
 457                                 range 1 to 65535, separated by a colon
 458                                 from a container port number in the
 459                                 range from 1 to 65535. The protocol
 460                                 specifier and its separating colon may
 461                                 be omitted, in which case
 462                                 <literal>tcp</literal> is assumed.
 463                                 The container port number and its
 464                                 colon may be ommitted, in which case
 465                                 the same port as the host port is
 466                                 implied. This option is only supported
 467                                 if private networking is used, such as
 468                                 <option>--network-veth</option> or
 469                                 <option>--network-bridge=</option>.</para></listitem>
 470                         </varlistentry>
 471
 472                         <varlistentry>
 473                                 <term><option>-Z</option></term>
 474                                 <term><option>--selinux-context=</option></term>
 475
 476                                 <listitem><para>Sets the SELinux
 477                                 security context to be used to label
 478                                 processes in the container.</para>
 479                                 </listitem>
 480                         </varlistentry>
 481
 482                         <varlistentry>
 483                                 <term><option>-L</option></term>
 484                                 <term><option>--selinux-apifs-context=</option></term>
 485
 486                                 <listitem><para>Sets the SELinux security
 487                                 context to be used to label files in
 488                                 the virtual API file systems in the
 489                                 container.</para>
 490                                 </listitem>
 491                         </varlistentry>
 492
 493                         <varlistentry>
 494                                 <term><option>--capability=</option></term>
 495
 496                                 <listitem><para>List one or more
 497                                 additional capabilities to grant the
 498                                 container. Takes a comma-separated
 499                                 list of capability names, see
 500                                 <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 501                                 for more information. Note that the
 502                                 following capabilities will be granted
 503                                 in any way: CAP_CHOWN,
 504                                 CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH,
 505                                 CAP_FOWNER, CAP_FSETID, CAP_IPC_OWNER,
 506                                 CAP_KILL, CAP_LEASE,
 507                                 CAP_LINUX_IMMUTABLE,
 508                                 CAP_NET_BIND_SERVICE,
 509                                 CAP_NET_BROADCAST, CAP_NET_RAW,
 510                                 CAP_SETGID, CAP_SETFCAP, CAP_SETPCAP,
 511                                 CAP_SETUID, CAP_SYS_ADMIN,
 512                                 CAP_SYS_CHROOT, CAP_SYS_NICE,
 513                                 CAP_SYS_PTRACE, CAP_SYS_TTY_CONFIG,
 514                                 CAP_SYS_RESOURCE, CAP_SYS_BOOT,
 515                                 CAP_AUDIT_WRITE,
 516                                 CAP_AUDIT_CONTROL. Also CAP_NET_ADMIN
 517                                 is retained if
 518                                 <option>--private-network</option> is
 519                                 specified. If the special value
 520                                 <literal>all</literal> is passed, all
 521                                 capabilities are
 522                                 retained.</para></listitem>
 523                         </varlistentry>
 524
 525                         <varlistentry>
 526                                 <term><option>--drop-capability=</option></term>
 527
 528                                 <listitem><para>Specify one or more
 529                                 additional capabilities to drop for
 530                                 the container. This allows running the
 531                                 container with fewer capabilities than
 532                                 the default (see above).</para></listitem>
 533                         </varlistentry>
 534
 535                         <varlistentry>
 536                                 <term><option>--link-journal=</option></term>
 537
 538                                 <listitem><para>Control whether the
 539                                 container's journal shall be made
 540                                 visible to the host system. If enabled,
 541                                 allows viewing the container's journal
 542                                 files from the host (but not vice
 543                                 versa). Takes one of
 544                                 <literal>no</literal>,
 545                                 <literal>host</literal>,
 546                                 <literal>try-host</literal>,
 547                                 <literal>guest</literal>,
 548                                 <literal>try-guest</literal>,
 549                                 <literal>auto</literal>. If
 550                                 <literal>no</literal>, the journal is
 551                                 not linked. If <literal>host</literal>,
 552                                 the journal files are stored on the
 553                                 host file system (beneath
 554                                 <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
 555                                 and the subdirectory is bind-mounted
 556                                 into the container at the same
 557                                 location. If <literal>guest</literal>,
 558                                 the journal files are stored on the
 559                                 guest file system (beneath
 560                                 <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
 561                                 and the subdirectory is symlinked into the host
 562                                 at the same location. <literal>try-host</literal>
 563                                 and <literal>try-guest</literal> do the same
 564                                 but do not fail if the host does not have
 565                                 persistent journalling enabled.
 566                                 If <literal>auto</literal> (the default),
 567                                 and the right subdirectory of
 568                                 <filename>/var/log/journal</filename>
 569                                 exists, it will be bind mounted
 570                                 into the container. If the
 571                                 subdirectory does not exist, no
 572                                 linking is performed. Effectively,
 573                                 booting a container once with
 574                                 <literal>guest</literal> or
 575                                 <literal>host</literal> will link the
 576                                 journal persistently if further on
 577                                 the default of <literal>auto</literal>
 578                                 is used.</para></listitem>
 579                         </varlistentry>
 580
 581                         <varlistentry>
 582                                 <term><option>-j</option></term>
 583
 584                                 <listitem><para>Equivalent to
 585                                 <option>--link-journal=try-guest</option>.</para></listitem>
 586                         </varlistentry>
 587
 588                         <varlistentry>
 589                                 <term><option>--read-only</option></term>
 590
 591                                 <listitem><para>Mount the root file
 592                                 system read-only for the
 593                                 container.</para></listitem>
 594                         </varlistentry>
 595
 596                         <varlistentry>
 597                                 <term><option>--bind=</option></term>
 598                                 <term><option>--bind-ro=</option></term>
 599
 600                                 <listitem><para>Bind mount a file or
 601                                 directory from the host into the
 602                                 container. Either takes a path
 603                                 argument -- in which case the
 604                                 specified path will be mounted from
 605                                 the host to the same path in the
 606                                 container --, or a colon-separated
 607                                 pair of paths -- in which case the
 608                                 first specified path is the source in
 609                                 the host, and the second path is the
 610                                 destination in the container. The
 611                                 <option>--bind-ro=</option> option
 612                                 creates read-only bind
 613                                 mounts.</para></listitem>
 614                         </varlistentry>
 615
 616                         <varlistentry>
 617                                 <term><option>--tmpfs=</option></term>
 618
 619                                 <listitem><para>Mount a tmpfs file
 620                                 system into the container. Takes a
 621                                 single absolute path argument that
 622                                 specifies where to mount the tmpfs
 623                                 instance to (in which case the
 624                                 directory access mode will be chosen
 625                                 as 0755, owned by root/root), or
 626                                 optionally a colon-separated pair of
 627                                 path and mount option string, that is
 628                                 used for mounting (in which case the
 629                                 kernel default for access mode and
 630                                 owner will be chosen, unless otherwise
 631                                 specified). This option is
 632                                 particularly useful for mounting
 633                                 directories such as
 634                                 <filename>/var</filename> as tmpfs, to
 635                                 allow state-less systems, in
 636                                 particular when combined with
 637                                 <option>--read-only</option>.</para></listitem>
 638                         </varlistentry>
 639
 640                         <varlistentry>
 641                                 <term><option>--setenv=</option></term>
 642
 643                                 <listitem><para>Specifies an
 644                                 environment variable assignment to
 645                                 pass to the init process in the
 646                                 container, in the format
 647                                 <literal>NAME=VALUE</literal>. This
 648                                 may be used to override the default
 649                                 variables or to set additional
 650                                 variables. This parameter may be used
 651                                 more than once.</para></listitem>
 652                         </varlistentry>
 653
 654                         <varlistentry>
 655                                 <term><option>--share-system</option></term>
 656
 657                                 <listitem><para>Allows the container
 658                                 to share certain system facilities
 659                                 with the host. More specifically, this
 660                                 turns off PID namespacing, UTS
 661                                 namespacing and IPC namespacing, and
 662                                 thus allows the guest to see and
 663                                 interact more easily with processes
 664                                 outside of the container. Note that
 665                                 using this option makes it impossible
 666                                 to start up a full Operating System in
 667                                 the container, as an init system
 668                                 cannot operate in this mode. It is
 669                                 only useful to run specific programs
 670                                 or applications this way, without
 671                                 involving an init system in the
 672                                 container. This option implies
 673                                 <option>--register=no</option>. This
 674                                 option may not be combined with
 675                                 <option>--boot</option>.</para></listitem>
 676                         </varlistentry>
 677
 678                         <varlistentry>
 679                                 <term><option>--register=</option></term>
 680
 681                                 <listitem><para>Controls whether the
 682                                 container is registered with
 683                                 <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>. Takes
 684                                 a boolean argument, defaults to
 685                                 <literal>yes</literal>. This option
 686                                 should be enabled when the container
 687                                 runs a full Operating System (more
 688                                 specifically: an init system), and is
 689                                 useful to ensure that the container is
 690                                 accessible via
 691                                 <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 692                                 and shown by tools such as
 693                                 <citerefentry project='man-pages'><refentrytitle>ps</refentrytitle><manvolnum>1</manvolnum></citerefentry>. If
 694                                 the container does not run an init
 695                                 system, it is recommended to set this
 696                                 option to <literal>no</literal>. Note
 697                                 that <option>--share-system</option>
 698                                 implies
 699                                 <option>--register=no</option>.
 700                                 </para></listitem>
 701                         </varlistentry>
 702
 703                         <varlistentry>
 704                                 <term><option>--keep-unit</option></term>
 705
 706                                 <listitem><para>Instead of creating a
 707                                 transient scope unit to run the
 708                                 container in, simply register the
 709                                 service or scope unit
 710                                 <command>systemd-nspawn</command> has
 711                                 been invoked in with
 712                                 <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>. This
 713                                 has no effect if
 714                                 <option>--register=no</option> is
 715                                 used. This switch should be used if
 716                                 <command>systemd-nspawn</command> is
 717                                 invoked from within a service unit,
 718                                 and the service unit's sole purpose
 719                                 is to run a single
 720                                 <command>systemd-nspawn</command>
 721                                 container. This option is not
 722                                 available if run from a user
 723                                 session.</para></listitem>
 724                         </varlistentry>
 725
 726                         <varlistentry>
 727                                 <term><option>--personality=</option></term>
 728
 729                                 <listitem><para>Control the
 730                                 architecture ("personality") reported
 731                                 by
 732                                 <citerefentry><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 733                                 in the container. Currently, only
 734                                 <literal>x86</literal> and
 735                                 <literal>x86-64</literal> are
 736                                 supported. This is useful when running
 737                                 a 32-bit container on a 64-bit
 738                                 host. If this setting is not used,
 739                                 the personality reported in the
 740                                 container is the same as the one
 741                                 reported on the
 742                                 host.</para></listitem>
 743                         </varlistentry>
 744
 745                         <varlistentry>
 746                                 <term><option>-q</option></term>
 747                                 <term><option>--quiet</option></term>
 748
 749                                 <listitem><para>Turns off any status
 750                                 output by the tool itself. When this
 751                                 switch is used, the only output
 752                                 from nspawn will be the console output
 753                                 of the container OS itself.</para></listitem>
 754                         </varlistentry>
 755
 756                         <varlistentry>
 757                                 <term><option>--volatile</option><replaceable>=MODE</replaceable></term>
 758
 759                                 <listitem><para>Boots the container in
 760                                 volatile mode. When no mode parameter
 761                                 is passed or when mode is specified as
 762                                 <literal>yes</literal> full volatile
 763                                 mode is enabled. This means the root
 764                                 directory is mounted as mostly
 765                                 unpopulated <literal>tmpfs</literal>
 766                                 instance, and
 767                                 <filename>/usr</filename> from the OS
 768                                 tree is mounted into it, read-only
 769                                 (the system thus starts up with
 770                                 read-only OS resources, but pristine
 771                                 state and configuration, any changes
 772                                 to the either are lost on
 773                                 shutdown). When the mode parameter is
 774                                 specified as <literal>state</literal>
 775                                 the OS tree is mounted read-only, but
 776                                 <filename>/var</filename> is mounted
 777                                 as <literal>tmpfs</literal> instance
 778                                 into it (the system thus starts up
 779                                 with read-only OS resources and
 780                                 configuration, but pristine state, any
 781                                 changes to the latter are lost on
 782                                 shutdown). When the mode parameter is
 783                                 specified as <literal>no</literal>
 784                                 (the default) the whole OS tree is
 785                                 made available writable.</para>
 786
 787                                 <para>Note that setting this to
 788                                 <literal>yes</literal> or
 789                                 <literal>state</literal> will only
 790                                 work correctly with operating systems
 791                                 in the container that can boot up with
 792                                 only <filename>/usr</filename>
 793                                 mounted, and are able to populate
 794                                 <filename>/var</filename>
 795                                 automatically, as
 796                                 needed.</para></listitem>
 797                         </varlistentry>
 798
 799                         <xi:include href="standard-options.xml" xpointer="help" />
 800                         <xi:include href="standard-options.xml" xpointer="version" />
 801                 </variablelist>
 802
 803         </refsect1>
 804
 805         <refsect1>
 806                 <title>Examples</title>
 807                 <example>
 808                         <title>Boot a minimal Fedora distribution in a container</title>
 809
 810                         <programlisting># yum -y --releasever=21 --nogpg --installroot=/srv/mycontainer --disablerepo='*' --enablerepo=fedora install systemd passwd yum fedora-release vim-minimal
 811 # systemd-nspawn -bD /srv/mycontainer</programlisting>
 812
 813                         <para>This installs a minimal Fedora distribution into
 814                         the directory <filename noindex='true'>/srv/mycontainer/</filename> and
 815                         then boots an OS in a namespace container in
 816                         it.</para>
 817                 </example>
 818
 819                 <example>
 820                         <title>Spawn a shell in a container of a minimal Debian unstable distribution</title>
 821
 822                         <programlisting># debootstrap --arch=amd64 unstable ~/debian-tree/
 823 # systemd-nspawn -D ~/debian-tree/</programlisting>
 824
 825                         <para>This installs a minimal Debian unstable
 826                         distribution into the directory
 827                         <filename>~/debian-tree/</filename> and then spawns a
 828                         shell in a namespace container in it.</para>
 829                 </example>
 830
 831                 <example>
 832                         <title>Boot a minimal Arch Linux distribution in a container</title>
 833
 834                         <programlisting># pacstrap -c -d ~/arch-tree/ base
 835 # systemd-nspawn -bD ~/arch-tree/</programlisting>
 836
 837                         <para>This installs a mimimal Arch Linux distribution into
 838                         the directory <filename>~/arch-tree/</filename> and then
 839                         boots an OS in a namespace container in it.</para>
 840                 </example>
 841
 842                 <example>
 843                         <title>Enable Arch Linux container on boot</title>
 844
 845                         <programlisting># mv ~/arch-tree /var/lib/container/arch
 846 # systemctl enable systemd-nspawn@arch.service
 847 # systemctl start systemd-nspawn@arch.service</programlisting>
 848
 849                         <para>This makes the Arch Linux container part of the
 850                         <filename>multi-user.target</filename> on the host.
 851                         </para>
 852                 </example>
 853
 854                 <example>
 855                         <title>Boot into an ephemeral <literal>btrfs</literal> snapshot of the host system</title>
 856
 857                         <programlisting># systemd-nspawn -D / -xb</programlisting>
 858
 859                         <para>This runs a copy of the host system in a
 860                         <literal>btrfs</literal> snapshot which is
 861                         removed immediately when the container
 862                         exits. All file system changes made during
 863                         runtime will be lost on shutdown,
 864                         hence.</para>
 865                 </example>
 866
 867                 <example>
 868                         <title>Run a container with SELinux sandbox security contexts</title>
 869
 870                         <programlisting># chcon system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -R /srv/container
 871 # 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>
 872                 </example>
 873         </refsect1>
 874
 875         <refsect1>
 876                 <title>Exit status</title>
 877
 878                 <para>The exit code of the program executed in the
 879                 container is returned.</para>
 880         </refsect1>
 881
 882         <refsect1>
 883                 <title>See Also</title>
 884                 <para>
 885                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 886                         <citerefentry project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 887                         <citerefentry project='die-net'><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 888                         <citerefentry project='die-net'><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 889                         <citerefentry project='archlinux'><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 890                         <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 891                         <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 892                         <citerefentry><refentrytitle>btrfs</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 893                 </para>
 894         </refsect1>
 895
 896 </refentry>