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/machines/</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 either an
 251                                 MBR partition table with a single
 252                                 partition of type 0x83 that is marked
 253                                 bootable, or a GUID partition table
 254                                 with a root partition which is mounted
 255                                 as the root directory of the
 256                                 container. Optionally, GPT images may
 257                                 contain a home and/or a server data
 258                                 partition which are mounted to the
 259                                 appropriate places in the
 260                                 container. All these partitions must
 261                                 be identified by the partition types
 262                                 defined by the <ulink
 263                                 url="http://www.freedesktop.org/wiki/Specifications/DiscoverablePartitionsSpec/">Discoverable
 264                                 Partitions Specification</ulink>. Any
 265                                 other partitions, such as foreign
 266                                 partitions, swap partitions or EFI
 267                                 system partitions are not mounted. May
 268                                 not be specified together with
 269                                 <option>--directory=</option>,
 270                                 <option>--template=</option> or
 271                                 <option>--ephemeral</option>.</para></listitem>
 272                         </varlistentry>
 273
 274                         <varlistentry>
 275                                 <term><option>-b</option></term>
 276                                 <term><option>--boot</option></term>
 277
 278                                 <listitem><para>Automatically search
 279                                 for an init binary and invoke it
 280                                 instead of a shell or a user supplied
 281                                 program. If this option is used,
 282                                 arguments specified on the command
 283                                 line are used as arguments for the
 284                                 init binary. This option may not be
 285                                 combined with
 286                                 <option>--share-system</option>.
 287                                 </para></listitem>
 288                         </varlistentry>
 289
 290                         <varlistentry>
 291                                 <term><option>-u</option></term>
 292                                 <term><option>--user=</option></term>
 293
 294                                 <listitem><para>After transitioning
 295                                 into the container, change to the
 296                                 specified user-defined in the
 297                                 container's user database. Like all
 298                                 other systemd-nspawn features, this is
 299                                 not a security feature and provides
 300                                 protection against accidental
 301                                 destructive operations
 302                                 only.</para></listitem>
 303                         </varlistentry>
 304
 305                         <varlistentry>
 306                                 <term><option>-M</option></term>
 307                                 <term><option>--machine=</option></term>
 308
 309                                 <listitem><para>Sets the machine name
 310                                 for this container. This name may be
 311                                 used to identify this container during
 312                                 its runtime (for example in tools like
 313                                 <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 314                                 and similar), and is used to
 315                                 initialize the container's hostname
 316                                 (which the container can choose to
 317                                 override, however). If not specified,
 318                                 the last component of the root
 319                                 directory path of the container is
 320                                 used, possibly suffixed with a random
 321                                 identifier in case
 322                                 <option>--ephemeral</option> mode is
 323                                 selected. If the root directory
 324                                 selected is the host's root directory
 325                                 the host's hostname is used as default
 326                                 instead.</para></listitem>
 327                         </varlistentry>
 328
 329                         <varlistentry>
 330                                 <term><option>--uuid=</option></term>
 331
 332                                 <listitem><para>Set the specified UUID
 333                                 for the container. The init system
 334                                 will initialize
 335                                 <filename>/etc/machine-id</filename>
 336                                 from this if this file is not set yet.
 337                                 </para></listitem>
 338                         </varlistentry>
 339
 340                         <varlistentry>
 341                                 <term><option>--slice=</option></term>
 342
 343                                 <listitem><para>Make the container
 344                                 part of the specified slice, instead
 345                                 of the default
 346                                 <filename>machine.slice</filename>.</para>
 347                                 </listitem>
 348                         </varlistentry>
 349
 350                         <varlistentry>
 351                                 <term><option>--private-network</option></term>
 352
 353                                 <listitem><para>Disconnect networking
 354                                 of the container from the host. This
 355                                 makes all network interfaces
 356                                 unavailable in the container, with the
 357                                 exception of the loopback device and
 358                                 those specified with
 359                                 <option>--network-interface=</option>
 360                                 and configured with
 361                                 <option>--network-veth</option>. If
 362                                 this option is specified, the
 363                                 CAP_NET_ADMIN capability will be added
 364                                 to the set of capabilities the
 365                                 container retains. The latter may be
 366                                 disabled by using
 367                                 <option>--drop-capability=</option>.</para></listitem>
 368                         </varlistentry>
 369
 370                         <varlistentry>
 371                                 <term><option>--network-interface=</option></term>
 372
 373                                 <listitem><para>Assign the specified
 374                                 network interface to the
 375                                 container. This will remove the
 376                                 specified interface from the calling
 377                                 namespace and place it in the
 378                                 container. When the container
 379                                 terminates, it is moved back to the
 380                                 host namespace. Note that
 381                                 <option>--network-interface=</option>
 382                                 implies
 383                                 <option>--private-network</option>. This
 384                                 option may be used more than once to
 385                                 add multiple network interfaces to the
 386                                 container.</para></listitem>
 387                         </varlistentry>
 388
 389                         <varlistentry>
 390                                 <term><option>--network-macvlan=</option></term>
 391
 392                                 <listitem><para>Create a
 393                                 <literal>macvlan</literal> interface
 394                                 of the specified Ethernet network
 395                                 interface and add it to the
 396                                 container. A
 397                                 <literal>macvlan</literal> interface
 398                                 is a virtual interface that adds a
 399                                 second MAC address to an existing
 400                                 physical Ethernet link. The interface
 401                                 in the container will be named after
 402                                 the interface on the host, prefixed
 403                                 with <literal>mv-</literal>. Note that
 404                                 <option>--network-macvlan=</option>
 405                                 implies
 406                                 <option>--private-network</option>. This
 407                                 option may be used more than once to
 408                                 add multiple network interfaces to the
 409                                 container.</para></listitem>
 410                         </varlistentry>
 411
 412                         <varlistentry>
 413                                 <term><option>-n</option></term>
 414                                 <term><option>--network-veth</option></term>
 415
 416                                 <listitem><para>Create a virtual
 417                                 Ethernet link
 418                                 (<literal>veth</literal>) between host
 419                                 and container. The host side of the
 420                                 Ethernet link will be available as a
 421                                 network interface named after the
 422                                 container's name (as specified with
 423                                 <option>--machine=</option>), prefixed
 424                                 with <literal>ve-</literal>. The
 425                                 container side of the Ethernet
 426                                 link will be named
 427                                 <literal>host0</literal>. Note that
 428                                 <option>--network-veth</option>
 429                                 implies
 430                                 <option>--private-network</option>.</para></listitem>
 431                         </varlistentry>
 432
 433                         <varlistentry>
 434                                 <term><option>--network-bridge=</option></term>
 435
 436                                 <listitem><para>Adds the host side of
 437                                 the Ethernet link created with
 438                                 <option>--network-veth</option> to the
 439                                 specified bridge. Note that
 440                                 <option>--network-bridge=</option>
 441                                 implies
 442                                 <option>--network-veth</option>. If
 443                                 this option is used, the host side of
 444                                 the Ethernet link will use the
 445                                 <literal>vb-</literal> prefix instead
 446                                 of <literal>ve-</literal>.</para></listitem>
 447                         </varlistentry>
 448
 449                         <varlistentry>
 450                                 <term><option>-p</option></term>
 451                                 <term><option>--port=</option></term>
 452
 453                                 <listitem><para>If private networking
 454                                 is enabled, maps an IP port on the
 455                                 host onto an IP port on the
 456                                 container. Takes a protocol specifier
 457                                 (either <literal>tcp</literal> or
 458                                 <literal>udp</literal>), separated by
 459                                 a colon from a host port number in the
 460                                 range 1 to 65535, separated by a colon
 461                                 from a container port number in the
 462                                 range from 1 to 65535. The protocol
 463                                 specifier and its separating colon may
 464                                 be omitted, in which case
 465                                 <literal>tcp</literal> is assumed.
 466                                 The container port number and its
 467                                 colon may be ommitted, in which case
 468                                 the same port as the host port is
 469                                 implied. This option is only supported
 470                                 if private networking is used, such as
 471                                 <option>--network-veth</option> or
 472                                 <option>--network-bridge=</option>.</para></listitem>
 473                         </varlistentry>
 474
 475                         <varlistentry>
 476                                 <term><option>-Z</option></term>
 477                                 <term><option>--selinux-context=</option></term>
 478
 479                                 <listitem><para>Sets the SELinux
 480                                 security context to be used to label
 481                                 processes in the container.</para>
 482                                 </listitem>
 483                         </varlistentry>
 484
 485                         <varlistentry>
 486                                 <term><option>-L</option></term>
 487                                 <term><option>--selinux-apifs-context=</option></term>
 488
 489                                 <listitem><para>Sets the SELinux security
 490                                 context to be used to label files in
 491                                 the virtual API file systems in the
 492                                 container.</para>
 493                                 </listitem>
 494                         </varlistentry>
 495
 496                         <varlistentry>
 497                                 <term><option>--capability=</option></term>
 498
 499                                 <listitem><para>List one or more
 500                                 additional capabilities to grant the
 501                                 container. Takes a comma-separated
 502                                 list of capability names, see
 503                                 <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 504                                 for more information. Note that the
 505                                 following capabilities will be granted
 506                                 in any way: CAP_CHOWN,
 507                                 CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH,
 508                                 CAP_FOWNER, CAP_FSETID, CAP_IPC_OWNER,
 509                                 CAP_KILL, CAP_LEASE,
 510                                 CAP_LINUX_IMMUTABLE,
 511                                 CAP_NET_BIND_SERVICE,
 512                                 CAP_NET_BROADCAST, CAP_NET_RAW,
 513                                 CAP_SETGID, CAP_SETFCAP, CAP_SETPCAP,
 514                                 CAP_SETUID, CAP_SYS_ADMIN,
 515                                 CAP_SYS_CHROOT, CAP_SYS_NICE,
 516                                 CAP_SYS_PTRACE, CAP_SYS_TTY_CONFIG,
 517                                 CAP_SYS_RESOURCE, CAP_SYS_BOOT,
 518                                 CAP_AUDIT_WRITE,
 519                                 CAP_AUDIT_CONTROL. Also CAP_NET_ADMIN
 520                                 is retained if
 521                                 <option>--private-network</option> is
 522                                 specified. If the special value
 523                                 <literal>all</literal> is passed, all
 524                                 capabilities are
 525                                 retained.</para></listitem>
 526                         </varlistentry>
 527
 528                         <varlistentry>
 529                                 <term><option>--drop-capability=</option></term>
 530
 531                                 <listitem><para>Specify one or more
 532                                 additional capabilities to drop for
 533                                 the container. This allows running the
 534                                 container with fewer capabilities than
 535                                 the default (see above).</para></listitem>
 536                         </varlistentry>
 537
 538                         <varlistentry>
 539                                 <term><option>--link-journal=</option></term>
 540
 541                                 <listitem><para>Control whether the
 542                                 container's journal shall be made
 543                                 visible to the host system. If enabled,
 544                                 allows viewing the container's journal
 545                                 files from the host (but not vice
 546                                 versa). Takes one of
 547                                 <literal>no</literal>,
 548                                 <literal>host</literal>,
 549                                 <literal>try-host</literal>,
 550                                 <literal>guest</literal>,
 551                                 <literal>try-guest</literal>,
 552                                 <literal>auto</literal>. If
 553                                 <literal>no</literal>, the journal is
 554                                 not linked. If <literal>host</literal>,
 555                                 the journal files are stored on the
 556                                 host file system (beneath
 557                                 <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
 558                                 and the subdirectory is bind-mounted
 559                                 into the container at the same
 560                                 location. If <literal>guest</literal>,
 561                                 the journal files are stored on the
 562                                 guest file system (beneath
 563                                 <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
 564                                 and the subdirectory is symlinked into the host
 565                                 at the same location. <literal>try-host</literal>
 566                                 and <literal>try-guest</literal> do the same
 567                                 but do not fail if the host does not have
 568                                 persistent journalling enabled.
 569                                 If <literal>auto</literal> (the default),
 570                                 and the right subdirectory of
 571                                 <filename>/var/log/journal</filename>
 572                                 exists, it will be bind mounted
 573                                 into the container. If the
 574                                 subdirectory does not exist, no
 575                                 linking is performed. Effectively,
 576                                 booting a container once with
 577                                 <literal>guest</literal> or
 578                                 <literal>host</literal> will link the
 579                                 journal persistently if further on
 580                                 the default of <literal>auto</literal>
 581                                 is used.</para></listitem>
 582                         </varlistentry>
 583
 584                         <varlistentry>
 585                                 <term><option>-j</option></term>
 586
 587                                 <listitem><para>Equivalent to
 588                                 <option>--link-journal=try-guest</option>.</para></listitem>
 589                         </varlistentry>
 590
 591                         <varlistentry>
 592                                 <term><option>--read-only</option></term>
 593
 594                                 <listitem><para>Mount the root file
 595                                 system read-only for the
 596                                 container.</para></listitem>
 597                         </varlistentry>
 598
 599                         <varlistentry>
 600                                 <term><option>--bind=</option></term>
 601                                 <term><option>--bind-ro=</option></term>
 602
 603                                 <listitem><para>Bind mount a file or
 604                                 directory from the host into the
 605                                 container. Either takes a path
 606                                 argument -- in which case the
 607                                 specified path will be mounted from
 608                                 the host to the same path in the
 609                                 container --, or a colon-separated
 610                                 pair of paths -- in which case the
 611                                 first specified path is the source in
 612                                 the host, and the second path is the
 613                                 destination in the container. The
 614                                 <option>--bind-ro=</option> option
 615                                 creates read-only bind
 616                                 mounts.</para></listitem>
 617                         </varlistentry>
 618
 619                         <varlistentry>
 620                                 <term><option>--tmpfs=</option></term>
 621
 622                                 <listitem><para>Mount a tmpfs file
 623                                 system into the container. Takes a
 624                                 single absolute path argument that
 625                                 specifies where to mount the tmpfs
 626                                 instance to (in which case the
 627                                 directory access mode will be chosen
 628                                 as 0755, owned by root/root), or
 629                                 optionally a colon-separated pair of
 630                                 path and mount option string, that is
 631                                 used for mounting (in which case the
 632                                 kernel default for access mode and
 633                                 owner will be chosen, unless otherwise
 634                                 specified). This option is
 635                                 particularly useful for mounting
 636                                 directories such as
 637                                 <filename>/var</filename> as tmpfs, to
 638                                 allow state-less systems, in
 639                                 particular when combined with
 640                                 <option>--read-only</option>.</para></listitem>
 641                         </varlistentry>
 642
 643                         <varlistentry>
 644                                 <term><option>--setenv=</option></term>
 645
 646                                 <listitem><para>Specifies an
 647                                 environment variable assignment to
 648                                 pass to the init process in the
 649                                 container, in the format
 650                                 <literal>NAME=VALUE</literal>. This
 651                                 may be used to override the default
 652                                 variables or to set additional
 653                                 variables. This parameter may be used
 654                                 more than once.</para></listitem>
 655                         </varlistentry>
 656
 657                         <varlistentry>
 658                                 <term><option>--share-system</option></term>
 659
 660                                 <listitem><para>Allows the container
 661                                 to share certain system facilities
 662                                 with the host. More specifically, this
 663                                 turns off PID namespacing, UTS
 664                                 namespacing and IPC namespacing, and
 665                                 thus allows the guest to see and
 666                                 interact more easily with processes
 667                                 outside of the container. Note that
 668                                 using this option makes it impossible
 669                                 to start up a full Operating System in
 670                                 the container, as an init system
 671                                 cannot operate in this mode. It is
 672                                 only useful to run specific programs
 673                                 or applications this way, without
 674                                 involving an init system in the
 675                                 container. This option implies
 676                                 <option>--register=no</option>. This
 677                                 option may not be combined with
 678                                 <option>--boot</option>.</para></listitem>
 679                         </varlistentry>
 680
 681                         <varlistentry>
 682                                 <term><option>--register=</option></term>
 683
 684                                 <listitem><para>Controls whether the
 685                                 container is registered with
 686                                 <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>. Takes
 687                                 a boolean argument, defaults to
 688                                 <literal>yes</literal>. This option
 689                                 should be enabled when the container
 690                                 runs a full Operating System (more
 691                                 specifically: an init system), and is
 692                                 useful to ensure that the container is
 693                                 accessible via
 694                                 <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 695                                 and shown by tools such as
 696                                 <citerefentry project='man-pages'><refentrytitle>ps</refentrytitle><manvolnum>1</manvolnum></citerefentry>. If
 697                                 the container does not run an init
 698                                 system, it is recommended to set this
 699                                 option to <literal>no</literal>. Note
 700                                 that <option>--share-system</option>
 701                                 implies
 702                                 <option>--register=no</option>.
 703                                 </para></listitem>
 704                         </varlistentry>
 705
 706                         <varlistentry>
 707                                 <term><option>--keep-unit</option></term>
 708
 709                                 <listitem><para>Instead of creating a
 710                                 transient scope unit to run the
 711                                 container in, simply register the
 712                                 service or scope unit
 713                                 <command>systemd-nspawn</command> has
 714                                 been invoked in with
 715                                 <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>. This
 716                                 has no effect if
 717                                 <option>--register=no</option> is
 718                                 used. This switch should be used if
 719                                 <command>systemd-nspawn</command> is
 720                                 invoked from within a service unit,
 721                                 and the service unit's sole purpose
 722                                 is to run a single
 723                                 <command>systemd-nspawn</command>
 724                                 container. This option is not
 725                                 available if run from a user
 726                                 session.</para></listitem>
 727                         </varlistentry>
 728
 729                         <varlistentry>
 730                                 <term><option>--personality=</option></term>
 731
 732                                 <listitem><para>Control the
 733                                 architecture ("personality") reported
 734                                 by
 735                                 <citerefentry><refentrytitle>uname</refentrytitle><manvolnum>2</manvolnum></citerefentry>
 736                                 in the container. Currently, only
 737                                 <literal>x86</literal> and
 738                                 <literal>x86-64</literal> are
 739                                 supported. This is useful when running
 740                                 a 32-bit container on a 64-bit
 741                                 host. If this setting is not used,
 742                                 the personality reported in the
 743                                 container is the same as the one
 744                                 reported on the
 745                                 host.</para></listitem>
 746                         </varlistentry>
 747
 748                         <varlistentry>
 749                                 <term><option>-q</option></term>
 750                                 <term><option>--quiet</option></term>
 751
 752                                 <listitem><para>Turns off any status
 753                                 output by the tool itself. When this
 754                                 switch is used, the only output
 755                                 from nspawn will be the console output
 756                                 of the container OS itself.</para></listitem>
 757                         </varlistentry>
 758
 759                         <varlistentry>
 760                                 <term><option>--volatile</option><replaceable>=MODE</replaceable></term>
 761
 762                                 <listitem><para>Boots the container in
 763                                 volatile mode. When no mode parameter
 764                                 is passed or when mode is specified as
 765                                 <literal>yes</literal> full volatile
 766                                 mode is enabled. This means the root
 767                                 directory is mounted as mostly
 768                                 unpopulated <literal>tmpfs</literal>
 769                                 instance, and
 770                                 <filename>/usr</filename> from the OS
 771                                 tree is mounted into it, read-only
 772                                 (the system thus starts up with
 773                                 read-only OS resources, but pristine
 774                                 state and configuration, any changes
 775                                 to the either are lost on
 776                                 shutdown). When the mode parameter is
 777                                 specified as <literal>state</literal>
 778                                 the OS tree is mounted read-only, but
 779                                 <filename>/var</filename> is mounted
 780                                 as <literal>tmpfs</literal> instance
 781                                 into it (the system thus starts up
 782                                 with read-only OS resources and
 783                                 configuration, but pristine state, any
 784                                 changes to the latter are lost on
 785                                 shutdown). When the mode parameter is
 786                                 specified as <literal>no</literal>
 787                                 (the default) the whole OS tree is
 788                                 made available writable.</para>
 789
 790                                 <para>Note that setting this to
 791                                 <literal>yes</literal> or
 792                                 <literal>state</literal> will only
 793                                 work correctly with operating systems
 794                                 in the container that can boot up with
 795                                 only <filename>/usr</filename>
 796                                 mounted, and are able to populate
 797                                 <filename>/var</filename>
 798                                 automatically, as
 799                                 needed.</para></listitem>
 800                         </varlistentry>
 801
 802                         <xi:include href="standard-options.xml" xpointer="help" />
 803                         <xi:include href="standard-options.xml" xpointer="version" />
 804                 </variablelist>
 805
 806         </refsect1>
 807
 808         <refsect1>
 809                 <title>Examples</title>
 810                 <example>
 811                         <title>Boot a minimal Fedora distribution in a container</title>
 812
 813                         <programlisting># yum -y --releasever=21 --nogpg --installroot=/srv/mycontainer --disablerepo='*' --enablerepo=fedora install systemd passwd yum fedora-release vim-minimal
 814 # systemd-nspawn -bD /srv/mycontainer</programlisting>
 815
 816                         <para>This installs a minimal Fedora distribution into
 817                         the directory <filename noindex='true'>/srv/mycontainer/</filename> and
 818                         then boots an OS in a namespace container in
 819                         it.</para>
 820                 </example>
 821
 822                 <example>
 823                         <title>Spawn a shell in a container of a minimal Debian unstable distribution</title>
 824
 825                         <programlisting># debootstrap --arch=amd64 unstable ~/debian-tree/
 826 # systemd-nspawn -D ~/debian-tree/</programlisting>
 827
 828                         <para>This installs a minimal Debian unstable
 829                         distribution into the directory
 830                         <filename>~/debian-tree/</filename> and then spawns a
 831                         shell in a namespace container in it.</para>
 832                 </example>
 833
 834                 <example>
 835                         <title>Boot a minimal Arch Linux distribution in a container</title>
 836
 837                         <programlisting># pacstrap -c -d ~/arch-tree/ base
 838 # systemd-nspawn -bD ~/arch-tree/</programlisting>
 839
 840                         <para>This installs a mimimal Arch Linux distribution into
 841                         the directory <filename>~/arch-tree/</filename> and then
 842                         boots an OS in a namespace container in it.</para>
 843                 </example>
 844
 845                 <example>
 846                         <title>Enable Arch Linux container on boot</title>
 847
 848                         <programlisting># mv ~/arch-tree /var/lib/machines/arch
 849 # systemctl enable systemd-nspawn@arch.service
 850 # systemctl start systemd-nspawn@arch.service</programlisting>
 851
 852                         <para>This makes the Arch Linux container part of the
 853                         <filename>multi-user.target</filename> on the host.
 854                         </para>
 855                 </example>
 856
 857                 <example>
 858                         <title>Boot into an ephemeral <literal>btrfs</literal> snapshot of the host system</title>
 859
 860                         <programlisting># systemd-nspawn -D / -xb</programlisting>
 861
 862                         <para>This runs a copy of the host system in a
 863                         <literal>btrfs</literal> snapshot which is
 864                         removed immediately when the container
 865                         exits. All file system changes made during
 866                         runtime will be lost on shutdown,
 867                         hence.</para>
 868                 </example>
 869
 870                 <example>
 871                         <title>Run a container with SELinux sandbox security contexts</title>
 872
 873                         <programlisting># chcon system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -R /srv/container
 874 # 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>
 875                 </example>
 876         </refsect1>
 877
 878         <refsect1>
 879                 <title>Exit status</title>
 880
 881                 <para>The exit code of the program executed in the
 882                 container is returned.</para>
 883         </refsect1>
 884
 885         <refsect1>
 886                 <title>See Also</title>
 887                 <para>
 888                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 889                         <citerefentry project='man-pages'><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 890                         <citerefentry project='die-net'><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 891                         <citerefentry project='die-net'><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 892                         <citerefentry project='archlinux'><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 893                         <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 894                         <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 895                         <citerefentry><refentrytitle>btrfs</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 896                 </para>
 897         </refsect1>
 898
 899 </refentry>