man/systemd-nspawn.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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   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
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  14
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  18   Lesser General Public License for more details.
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  23
  24 <refentry id="systemd-nspawn">
  25
  26         <refentryinfo>
  27                 <title>systemd-nspawn</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>systemd-nspawn</refentrytitle>
  42                 <manvolnum>1</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd-nspawn</refname>
  47                 <refpurpose>Spawn a namespace container for debugging, testing and building</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <cmdsynopsis>
  52                         <command>systemd-nspawn</command>
  53                         <arg choice="opt" rep="repeat">OPTIONS</arg>
  54                         <arg choice="opt"><replaceable>COMMAND</replaceable>
  55                         <arg choice="opt" rep="repeat">ARGS</arg>
  56                         </arg>
  57                 </cmdsynopsis>
  58                 <cmdsynopsis>
  59                         <command>systemd-nspawn</command>
  60                         <arg choice="plain">-b</arg>
  61                         <arg choice="opt" rep="repeat">OPTIONS</arg>
  62                         <arg choice="opt" rep="repeat">ARGS</arg>
  63                 </cmdsynopsis>
  64         </refsynopsisdiv>
  65
  66         <refsect1>
  67                 <title>Description</title>
  68
  69                 <para><command>systemd-nspawn</command> may be used to
  70                 run a command or OS in a light-weight namespace
  71                 container. In many ways it is similar to
  72                 <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
  73                 but more powerful since it fully virtualizes the file
  74                 system hierarchy, as well as the process tree, the
  75                 various IPC subsystems and the host and domain
  76                 name.</para>
  77
  78                 <para><command>systemd-nspawn</command> limits access
  79                 to various kernel interfaces in the container to
  80                 read-only, such as <filename>/sys</filename>,
  81                 <filename>/proc/sys</filename> or
  82                 <filename>/sys/fs/selinux</filename>. Network
  83                 interfaces and the system clock may not be changed
  84                 from within the container. Device nodes may not be
  85                 created. The host system cannot be rebooted and kernel
  86                 modules may not be loaded from within the
  87                 container.</para>
  88
  89                 <para>Note that even though these security precautions
  90                 are taken <command>systemd-nspawn</command> is not
  91                 suitable for secure container setups. Many of the
  92                 security features may be circumvented and are hence
  93                 primarily useful to avoid accidental changes to the
  94                 host system from the container. The intended use of
  95                 this program is debugging and testing as well as
  96                 building of packages, distributions and software
  97                 involved with boot and systems management.</para>
  98
  99                 <para>In contrast to
 100                 <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry> <command>systemd-nspawn</command>
 101                 may be used to boot full Linux-based operating systems
 102                 in a container.</para>
 103
 104                 <para>Use a tool like
 105                 <citerefentry><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 106                 <citerefentry><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 107                 or
 108                 <citerefentry><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 109                 to set up an OS directory tree suitable as file system
 110                 hierarchy for <command>systemd-nspawn</command>
 111                 containers.</para>
 112
 113                 <para>Note that <command>systemd-nspawn</command> will
 114                 mount file systems private to the container to
 115                 <filename>/dev</filename>,
 116                 <filename>/run</filename> and similar. These will
 117                 not be visible outside of the container, and their
 118                 contents will be lost when the container exits.</para>
 119
 120                 <para>Note that running two
 121                 <command>systemd-nspawn</command> containers from the
 122                 same directory tree will not make processes in them
 123                 see each other. The PID namespace separation of the
 124                 two containers is complete and the containers will
 125                 share very few runtime objects except for the
 126                 underlying file system. Use
 127                 <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
 128                 <command>login</command> command to request an
 129                 additional login prompt in a running container.</para>
 130
 131                 <para><command>systemd-nspawn</command> implements the
 132                 <ulink
 133                 url="http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface">Container
 134                 Interface</ulink> specification.</para>
 135
 136                 <para>As a safety check
 137                 <command>systemd-nspawn</command> will verify the
 138                 existence of <filename>/etc/os-release</filename> in
 139                 the container tree before starting the container (see
 140                 <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>). It
 141                 might be necessary to add this file to the container
 142                 tree manually if the OS of the container is too old to
 143                 contain this file out-of-the-box.</para>
 144         </refsect1>
 145
 146         <refsect1>
 147                 <title>Options</title>
 148
 149                 <para>If option <option>-b</option> is specified, the
 150                 arguments are used as arguments for the init
 151                 binary. Otherwise, <replaceable>COMMAND</replaceable>
 152                 specifies the program to launch in the container, and
 153                 the remaining arguments are used as arguments for this
 154                 program. If <option>-b</option> is not used and no
 155                 arguments are specifed, a shell is launched in the
 156                 container.</para>
 157
 158                 <para>The following options are understood:</para>
 159
 160                 <variablelist>
 161                         <varlistentry>
 162                                 <term><option>-h</option></term>
 163                                 <term><option>--help</option></term>
 164
 165                                 <listitem><para>Prints a short help
 166                                 text and exits.</para></listitem>
 167                         </varlistentry>
 168
 169                         <varlistentry>
 170                                 <term><option>--version</option></term>
 171
 172                                 <listitem><para>Prints a version string
 173                                 and exits.</para></listitem>
 174                         </varlistentry>
 175
 176                         <varlistentry>
 177                                 <term><option>-D</option></term>
 178                                 <term><option>--directory=</option></term>
 179
 180                                 <listitem><para>Directory to use as
 181                                 file system root for the namespace
 182                                 container. If omitted, the current
 183                                 directory will be
 184                                 used.</para></listitem>
 185                         </varlistentry>
 186
 187                         <varlistentry>
 188                                 <term><option>-b</option></term>
 189                                 <term><option>--boot</option></term>
 190
 191                                 <listitem><para>Automatically search
 192                                 for an init binary and invoke it
 193                                 instead of a shell or a user supplied
 194                                 program. If this option is used,
 195                                 arguments specified on the command
 196                                 line are used as arguments for the
 197                                 init binary. This option may not be
 198                                 combined with
 199                                 <option>--share-system</option>.
 200                                 </para></listitem>
 201                         </varlistentry>
 202
 203                         <varlistentry>
 204                                 <term><option>-u</option></term>
 205                                 <term><option>--user=</option></term>
 206
 207                                 <listitem><para>Run the command
 208                                 under specified user, create home
 209                                 directory and cd into it. As rest
 210                                 of systemd-nspawn, this is not
 211                                 the security feature and limits
 212                                 against accidental changes only.
 213                                 </para></listitem>
 214                         </varlistentry>
 215
 216                         <varlistentry>
 217                                 <term><option>-M</option></term>
 218                                 <term><option>--machine=</option></term>
 219
 220                                 <listitem><para>Sets the machine name
 221                                 for this container. This name may be
 222                                 used to identify this container on the
 223                                 host, and is used to initialize the
 224                                 container's hostname (which the
 225                                 container can choose to override,
 226                                 however). If not specified, the last
 227                                 component of the root directory of the
 228                                 container is used.</para></listitem>
 229                         </varlistentry>
 230
 231                         <varlistentry>
 232                                 <term><option>--slice=</option></term>
 233
 234                                 <listitem><para>Make the container
 235                                 part of the specified slice, instead
 236                                 of the
 237                                 <filename>machine.slice</filename>.</para>
 238                                 </listitem>
 239                         </varlistentry>
 240
 241                         <varlistentry>
 242                                 <term><option>-Z</option></term>
 243                                 <term><option>--selinux-context=</option></term>
 244
 245                                 <listitem><para>Sets the SELinux
 246                                 security context to be used to label
 247                                 processes in the container.</para>
 248                                 </listitem>
 249                         </varlistentry>
 250
 251                         <varlistentry>
 252                                 <term><option>-L</option></term>
 253                                 <term><option>--selinux-apifs-context=</option></term>
 254
 255                                 <listitem><para>Sets the SELinux security
 256                                 context to be used to label files in
 257                                 the virtual API file systems in the
 258                                 container.</para>
 259                                 </listitem>
 260                         </varlistentry>
 261
 262                         <varlistentry>
 263                                 <term><option>--uuid=</option></term>
 264
 265                                 <listitem><para>Set the specified UUID
 266                                 for the container. The init system
 267                                 will initialize
 268                                 <filename>/etc/machine-id</filename>
 269                                 from this if this file is not set yet.
 270                                 </para></listitem>
 271                         </varlistentry>
 272
 273                         <varlistentry>
 274                                 <term><option>--private-network</option></term>
 275
 276                                 <listitem><para>Turn off networking in
 277                                 the container. This makes all network
 278                                 interfaces unavailable in the
 279                                 container, with the exception of the
 280                                 loopback device.</para></listitem>
 281                         </varlistentry>
 282
 283                         <varlistentry>
 284                                 <term><option>--network-interface=</option></term>
 285
 286                                 <listitem><para>Assign the specified
 287                                 network interface to the
 288                                 container. This will move the
 289                                 specified interface from the calling
 290                                 namespace and place it in the
 291                                 container. When the container
 292                                 terminates it is moved back to the
 293                                 host namespace.</para></listitem>
 294                         </varlistentry>
 295
 296                         <varlistentry>
 297                                 <term><option>--read-only</option></term>
 298
 299                                 <listitem><para>Mount the root file
 300                                 system read-only for the
 301                                 container.</para></listitem>
 302                         </varlistentry>
 303
 304                         <varlistentry>
 305                                 <term><option>--capability=</option></term>
 306
 307                                 <listitem><para>List one or more
 308                                 additional capabilities to grant the
 309                                 container. Takes a comma-separated
 310                                 list of capability names, see
 311                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 312                                 for more information. Note that the
 313                                 following capabilities will be granted
 314                                 in any way: CAP_CHOWN,
 315                                 CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH,
 316                                 CAP_FOWNER, CAP_FSETID, CAP_IPC_OWNER,
 317                                 CAP_KILL, CAP_LEASE,
 318                                 CAP_LINUX_IMMUTABLE,
 319                                 CAP_NET_BIND_SERVICE,
 320                                 CAP_NET_BROADCAST, CAP_NET_RAW,
 321                                 CAP_SETGID, CAP_SETFCAP, CAP_SETPCAP,
 322                                 CAP_SETUID, CAP_SYS_ADMIN,
 323                                 CAP_SYS_CHROOT, CAP_SYS_NICE,
 324                                 CAP_SYS_PTRACE, CAP_SYS_TTY_CONFIG,
 325                                 CAP_SYS_RESOURCE, CAP_SYS_BOOT,
 326                                 CAP_AUDIT_WRITE, CAP_AUDIT_CONTROL. If
 327                                 the special value
 328                                 <literal>all</literal> is passed all
 329                                 capabilities are
 330                                 retained.</para></listitem>
 331                         </varlistentry>
 332
 333                         <varlistentry>
 334                                 <term><option>--drop-capability=</option></term>
 335
 336                                 <listitem><para>Specify one or more
 337                                 additional capabilities to drop for
 338                                 the container. This allows running the
 339                                 container with fewer capabilities than
 340                                 the default (see above).</para></listitem>
 341                         </varlistentry>
 342
 343                         <varlistentry>
 344                                 <term><option>--link-journal=</option></term>
 345
 346                                 <listitem><para>Control whether the
 347                                 container's journal shall be made
 348                                 visible to the host system. If enabled,
 349                                 allows viewing the container's journal
 350                                 files from the host (but not vice
 351                                 versa). Takes one of
 352                                 <literal>no</literal>,
 353                                 <literal>host</literal>,
 354                                 <literal>guest</literal>,
 355                                 <literal>auto</literal>. If
 356                                 <literal>no</literal>, the journal is
 357                                 not linked. If <literal>host</literal>,
 358                                 the journal files are stored on the
 359                                 host file system (beneath
 360                                 <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
 361                                 and the subdirectory is bind-mounted
 362                                 into the container at the same
 363                                 location. If <literal>guest</literal>,
 364                                 the journal files are stored on the
 365                                 guest file system (beneath
 366                                 <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
 367                                 and the subdirectory is symlinked into the host
 368                                 at the same location. If
 369                                 <literal>auto</literal> (the default),
 370                                 and the right subdirectory of
 371                                 <filename>/var/log/journal</filename>
 372                                 exists, it will be bind mounted
 373                                 into the container. If the
 374                                 subdirectory does not exist, no
 375                                 linking is performed. Effectively,
 376                                 booting a container once with
 377                                 <literal>guest</literal> or
 378                                 <literal>host</literal> will link the
 379                                 journal persistently if further on
 380                                 the default of <literal>auto</literal>
 381                                 is used.</para></listitem>
 382                         </varlistentry>
 383
 384                         <varlistentry>
 385                                 <term><option>-j</option></term>
 386
 387                                 <listitem><para>Equivalent to
 388                                 <option>--link-journal=guest</option>.</para></listitem>
 389                         </varlistentry>
 390
 391                         <varlistentry>
 392                                 <term><option>--bind=</option></term>
 393                                 <term><option>--bind-ro=</option></term>
 394
 395                                 <listitem><para>Bind mount a file or
 396                                 directory from the host into the
 397                                 container. Either takes a path
 398                                 argument -- in which case the
 399                                 specified path will be mounted from
 400                                 the host to the same path in the
 401                                 container --, or a colon-separated
 402                                 pair of paths -- in which case the
 403                                 first specified path is the source in
 404                                 the host, and the second path is the
 405                                 destination in the container. The
 406                                 <option>--bind-ro=</option> option
 407                                 creates read-only bind
 408                                 mount.</para></listitem>
 409                         </varlistentry>
 410
 411                         <varlistentry>
 412                                 <term><option>--setenv=</option></term>
 413
 414                                 <listitem><para>Specifies an
 415                                 environment variable assignment to
 416                                 pass to the init process in the
 417                                 container, in the format
 418                                 <literal>NAME=VALUE</literal>. This
 419                                 may be used to override the default
 420                                 variables or to set additional
 421                                 variables. This parameter may be used
 422                                 more than once.</para></listitem>
 423                         </varlistentry>
 424
 425                         <varlistentry>
 426                                 <term><option>-q</option></term>
 427                                 <term><option>--quiet</option></term>
 428
 429                                 <listitem><para>Turns off any status
 430                                 output by the tool itself. When this
 431                                 switch is used, then the only output
 432                                 by nspawn will be the console output
 433                                 of the container OS itself.</para></listitem>
 434                         </varlistentry>
 435
 436                         <varlistentry>
 437                                 <term><option>--share-system</option></term>
 438
 439                                 <listitem><para>Allows the container
 440                                 to share certain system facilities
 441                                 with the host. More specifically, this
 442                                 turns off PID namespacing, UTS
 443                                 namespacing and IPC namespacing, and
 444                                 thus allows the guest to see and
 445                                 interact more easily with processes
 446                                 outside of the container. Note that
 447                                 using this option makes it impossible
 448                                 to start up a full Operating System in
 449                                 the container, as an init system
 450                                 cannot operate in this mode. It is
 451                                 only useful to run specific programs
 452                                 or applications this way, without
 453                                 involving an init system in the
 454                                 container. This option implies
 455                                 <option>--register=no</option>. This
 456                                 option may not be combined with
 457                                 <option>--boot</option>.</para></listitem>
 458                         </varlistentry>
 459
 460                         <varlistentry>
 461                                 <term><option>--register=</option></term>
 462
 463                                 <listitem><para>Controls whether the
 464                                 container is registered with
 465                                 <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>. Takes
 466                                 a boolean argument, defaults to
 467                                 <literal>yes</literal>. This option
 468                                 should be enabled when the container
 469                                 runs a full Operating System (more
 470                                 specifically: an init system), and is
 471                                 useful to ensure that the container is
 472                                 accessible via
 473                                 <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 474                                 and shown by tools such as
 475                                 <citerefentry><refentrytitle>ps</refentrytitle><manvolnum>1</manvolnum></citerefentry>. If
 476                                 the container does not run an init
 477                                 system it is recommended to set this
 478                                 option to <literal>no</literal>. Note
 479                                 that <option>--share-system</option>
 480                                 implies
 481                                 <option>--register=no</option>.
 482                                 </para></listitem>
 483                         </varlistentry>
 484
 485                         <varlistentry>
 486                                 <term><option>--keep-unit</option></term>
 487
 488                                 <listitem><para>Instead of creating a
 489                                 transient scope unit to run the
 490                                 container in, simply register the
 491                                 service or scope unit
 492                                 <command>systemd-nspawn</command> has
 493                                 been invoked in in
 494                                 <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>. This
 495                                 has no effect if
 496                                 <option>--register=no</option> is
 497                                 used. This switch should be used if
 498                                 <command>systemd-nspawn</command> is
 499                                 invoked from within an a service unit,
 500                                 and the service unit's sole purpose
 501                                 is to run a single
 502                                 <command>systemd-nspawn</command>
 503                                 container. This option is not
 504                                 available if run from a user
 505                                 session.</para></listitem>
 506                         </varlistentry>
 507
 508                 </variablelist>
 509
 510         </refsect1>
 511
 512         <refsect1>
 513                 <title>Example 1</title>
 514
 515                 <programlisting># yum -y --releasever=19 --nogpg --installroot=/srv/mycontainer --disablerepo='*' --enablerepo=fedora install systemd passwd yum fedora-release vim-minimal
 516 # systemd-nspawn -bD /srv/mycontainer</programlisting>
 517
 518                 <para>This installs a minimal Fedora distribution into
 519                 the directory <filename noindex='true'>/srv/mycontainer/</filename> and
 520                 then boots an OS in a namespace container in
 521                 it.</para>
 522         </refsect1>
 523
 524         <refsect1>
 525                 <title>Example 2</title>
 526
 527                 <programlisting># debootstrap --arch=amd64 unstable ~/debian-tree/
 528 # systemd-nspawn -D ~/debian-tree/</programlisting>
 529
 530                 <para>This installs a minimal Debian unstable
 531                 distribution into the directory
 532                 <filename>~/debian-tree/</filename> and then spawns a
 533                 shell in a namespace container in it.</para>
 534         </refsect1>
 535
 536         <refsect1>
 537                 <title>Example 3</title>
 538
 539                 <programlisting># pacstrap -c -d ~/arch-tree/ base
 540 # systemd-nspawn -bD ~/arch-tree/</programlisting>
 541
 542                 <para>This installs a mimimal Arch Linux distribution into
 543                 the directory <filename>~/arch-tree/</filename> and then
 544                 boots an OS in a namespace container in it.</para>
 545         </refsect1>
 546
 547         <refsect1>
 548                 <title>Example 4</title>
 549
 550                 <programlisting># mv ~/arch-tree /var/lib/container/arch
 551 # systemctl enable systemd-nspawn@arch.service
 552 # systemctl start systemd-nspawn@arch.service</programlisting>
 553
 554                 <para>This makes the Arch Linux container part of the
 555                 <filename>multi-user.target</filename> on the host.
 556                 </para>
 557         </refsect1>
 558
 559         <refsect1>
 560                 <title>Example 5</title>
 561
 562                 <programlisting># btrfs subvolume snapshot / /.tmp
 563 # systemd-nspawn --private-network -D /.tmp -b</programlisting>
 564
 565                 <para>This runs a copy of the host system in a
 566                 btrfs snapshot.</para>
 567         </refsect1>
 568
 569         <refsect1>
 570                 <title>Example 6</title>
 571
 572                 <programlisting># chcon system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -R /srv/container
 573 # 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>
 574
 575                 <para>This runs a container with SELinux sandbox security contexts.</para>
 576         </refsect1>
 577
 578         <refsect1>
 579                 <title>Exit status</title>
 580
 581                 <para>The exit code of the program executed in the
 582                 container is returned.</para>
 583         </refsect1>
 584
 585         <refsect1>
 586                 <title>See Also</title>
 587                 <para>
 588                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 589                         <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 590                         <citerefentry><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 591                         <citerefentry><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 592                         <citerefentry><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 593                         <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 594                         <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 595                 </para>
 596         </refsect1>
 597
 598 </refentry>