man/systemd-nspawn.xml

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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 and those specified
 281                                 with
 282                                 <option>--network-interface=</option>. If
 283                                 this option is specified the
 284                                 CAP_NET_ADMIN capability will be added
 285                                 to the set of capabilities the
 286                                 container retains. The latter may be
 287                                 disabled by using
 288                                 <option>--drop-capability=</option>.</para></listitem>
 289                         </varlistentry>
 290
 291                         <varlistentry>
 292                                 <term><option>--network-interface=</option></term>
 293
 294                                 <listitem><para>Assign the specified
 295                                 network interface to the
 296                                 container. This will move the
 297                                 specified interface from the calling
 298                                 namespace and place it in the
 299                                 container. When the container
 300                                 terminates it is moved back to the
 301                                 host namespace. Note that
 302                                 <option>--network-interface=</option>
 303                                 implies
 304                                 <option>--private-network</option>. This
 305                                 option may be used more than once to
 306                                 add multiple network interfaces to the
 307                                 container.</para></listitem>
 308                         </varlistentry>
 309
 310                         <varlistentry>
 311                                 <term><option>--read-only</option></term>
 312
 313                                 <listitem><para>Mount the root file
 314                                 system read-only for the
 315                                 container.</para></listitem>
 316                         </varlistentry>
 317
 318                         <varlistentry>
 319                                 <term><option>--capability=</option></term>
 320
 321                                 <listitem><para>List one or more
 322                                 additional capabilities to grant the
 323                                 container. Takes a comma-separated
 324                                 list of capability names, see
 325                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 326                                 for more information. Note that the
 327                                 following capabilities will be granted
 328                                 in any way: CAP_CHOWN,
 329                                 CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH,
 330                                 CAP_FOWNER, CAP_FSETID, CAP_IPC_OWNER,
 331                                 CAP_KILL, CAP_LEASE,
 332                                 CAP_LINUX_IMMUTABLE,
 333                                 CAP_NET_BIND_SERVICE,
 334                                 CAP_NET_BROADCAST, CAP_NET_RAW,
 335                                 CAP_SETGID, CAP_SETFCAP, CAP_SETPCAP,
 336                                 CAP_SETUID, CAP_SYS_ADMIN,
 337                                 CAP_SYS_CHROOT, CAP_SYS_NICE,
 338                                 CAP_SYS_PTRACE, CAP_SYS_TTY_CONFIG,
 339                                 CAP_SYS_RESOURCE, CAP_SYS_BOOT,
 340                                 CAP_AUDIT_WRITE,
 341                                 CAP_AUDIT_CONTROL. Also CAP_NET_ADMIN
 342                                 is retained if
 343                                 <option>--private-network</option> is
 344                                 specified. If the special value
 345                                 <literal>all</literal> is passed all
 346                                 capabilities are
 347                                 retained.</para></listitem>
 348                         </varlistentry>
 349
 350                         <varlistentry>
 351                                 <term><option>--drop-capability=</option></term>
 352
 353                                 <listitem><para>Specify one or more
 354                                 additional capabilities to drop for
 355                                 the container. This allows running the
 356                                 container with fewer capabilities than
 357                                 the default (see above).</para></listitem>
 358                         </varlistentry>
 359
 360                         <varlistentry>
 361                                 <term><option>--link-journal=</option></term>
 362
 363                                 <listitem><para>Control whether the
 364                                 container's journal shall be made
 365                                 visible to the host system. If enabled,
 366                                 allows viewing the container's journal
 367                                 files from the host (but not vice
 368                                 versa). Takes one of
 369                                 <literal>no</literal>,
 370                                 <literal>host</literal>,
 371                                 <literal>guest</literal>,
 372                                 <literal>auto</literal>. If
 373                                 <literal>no</literal>, the journal is
 374                                 not linked. If <literal>host</literal>,
 375                                 the journal files are stored on the
 376                                 host file system (beneath
 377                                 <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
 378                                 and the subdirectory is bind-mounted
 379                                 into the container at the same
 380                                 location. If <literal>guest</literal>,
 381                                 the journal files are stored on the
 382                                 guest file system (beneath
 383                                 <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
 384                                 and the subdirectory is symlinked into the host
 385                                 at the same location. If
 386                                 <literal>auto</literal> (the default),
 387                                 and the right subdirectory of
 388                                 <filename>/var/log/journal</filename>
 389                                 exists, it will be bind mounted
 390                                 into the container. If the
 391                                 subdirectory does not exist, no
 392                                 linking is performed. Effectively,
 393                                 booting a container once with
 394                                 <literal>guest</literal> or
 395                                 <literal>host</literal> will link the
 396                                 journal persistently if further on
 397                                 the default of <literal>auto</literal>
 398                                 is used.</para></listitem>
 399                         </varlistentry>
 400
 401                         <varlistentry>
 402                                 <term><option>-j</option></term>
 403
 404                                 <listitem><para>Equivalent to
 405                                 <option>--link-journal=guest</option>.</para></listitem>
 406                         </varlistentry>
 407
 408                         <varlistentry>
 409                                 <term><option>--bind=</option></term>
 410                                 <term><option>--bind-ro=</option></term>
 411
 412                                 <listitem><para>Bind mount a file or
 413                                 directory from the host into the
 414                                 container. Either takes a path
 415                                 argument -- in which case the
 416                                 specified path will be mounted from
 417                                 the host to the same path in the
 418                                 container --, or a colon-separated
 419                                 pair of paths -- in which case the
 420                                 first specified path is the source in
 421                                 the host, and the second path is the
 422                                 destination in the container. The
 423                                 <option>--bind-ro=</option> option
 424                                 creates read-only bind
 425                                 mount.</para></listitem>
 426                         </varlistentry>
 427
 428                         <varlistentry>
 429                                 <term><option>--setenv=</option></term>
 430
 431                                 <listitem><para>Specifies an
 432                                 environment variable assignment to
 433                                 pass to the init process in the
 434                                 container, in the format
 435                                 <literal>NAME=VALUE</literal>. This
 436                                 may be used to override the default
 437                                 variables or to set additional
 438                                 variables. This parameter may be used
 439                                 more than once.</para></listitem>
 440                         </varlistentry>
 441
 442                         <varlistentry>
 443                                 <term><option>-q</option></term>
 444                                 <term><option>--quiet</option></term>
 445
 446                                 <listitem><para>Turns off any status
 447                                 output by the tool itself. When this
 448                                 switch is used, then the only output
 449                                 by nspawn will be the console output
 450                                 of the container OS itself.</para></listitem>
 451                         </varlistentry>
 452
 453                         <varlistentry>
 454                                 <term><option>--share-system</option></term>
 455
 456                                 <listitem><para>Allows the container
 457                                 to share certain system facilities
 458                                 with the host. More specifically, this
 459                                 turns off PID namespacing, UTS
 460                                 namespacing and IPC namespacing, and
 461                                 thus allows the guest to see and
 462                                 interact more easily with processes
 463                                 outside of the container. Note that
 464                                 using this option makes it impossible
 465                                 to start up a full Operating System in
 466                                 the container, as an init system
 467                                 cannot operate in this mode. It is
 468                                 only useful to run specific programs
 469                                 or applications this way, without
 470                                 involving an init system in the
 471                                 container. This option implies
 472                                 <option>--register=no</option>. This
 473                                 option may not be combined with
 474                                 <option>--boot</option>.</para></listitem>
 475                         </varlistentry>
 476
 477                         <varlistentry>
 478                                 <term><option>--register=</option></term>
 479
 480                                 <listitem><para>Controls whether the
 481                                 container is registered with
 482                                 <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>. Takes
 483                                 a boolean argument, defaults to
 484                                 <literal>yes</literal>. This option
 485                                 should be enabled when the container
 486                                 runs a full Operating System (more
 487                                 specifically: an init system), and is
 488                                 useful to ensure that the container is
 489                                 accessible via
 490                                 <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 491                                 and shown by tools such as
 492                                 <citerefentry><refentrytitle>ps</refentrytitle><manvolnum>1</manvolnum></citerefentry>. If
 493                                 the container does not run an init
 494                                 system it is recommended to set this
 495                                 option to <literal>no</literal>. Note
 496                                 that <option>--share-system</option>
 497                                 implies
 498                                 <option>--register=no</option>.
 499                                 </para></listitem>
 500                         </varlistentry>
 501
 502                         <varlistentry>
 503                                 <term><option>--keep-unit</option></term>
 504
 505                                 <listitem><para>Instead of creating a
 506                                 transient scope unit to run the
 507                                 container in, simply register the
 508                                 service or scope unit
 509                                 <command>systemd-nspawn</command> has
 510                                 been invoked in in
 511                                 <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>. This
 512                                 has no effect if
 513                                 <option>--register=no</option> is
 514                                 used. This switch should be used if
 515                                 <command>systemd-nspawn</command> is
 516                                 invoked from within an a service unit,
 517                                 and the service unit's sole purpose
 518                                 is to run a single
 519                                 <command>systemd-nspawn</command>
 520                                 container. This option is not
 521                                 available if run from a user
 522                                 session.</para></listitem>
 523                         </varlistentry>
 524
 525                 </variablelist>
 526
 527         </refsect1>
 528
 529         <refsect1>
 530                 <title>Example 1</title>
 531
 532                 <programlisting># yum -y --releasever=19 --nogpg --installroot=/srv/mycontainer --disablerepo='*' --enablerepo=fedora install systemd passwd yum fedora-release vim-minimal
 533 # systemd-nspawn -bD /srv/mycontainer</programlisting>
 534
 535                 <para>This installs a minimal Fedora distribution into
 536                 the directory <filename noindex='true'>/srv/mycontainer/</filename> and
 537                 then boots an OS in a namespace container in
 538                 it.</para>
 539         </refsect1>
 540
 541         <refsect1>
 542                 <title>Example 2</title>
 543
 544                 <programlisting># debootstrap --arch=amd64 unstable ~/debian-tree/
 545 # systemd-nspawn -D ~/debian-tree/</programlisting>
 546
 547                 <para>This installs a minimal Debian unstable
 548                 distribution into the directory
 549                 <filename>~/debian-tree/</filename> and then spawns a
 550                 shell in a namespace container in it.</para>
 551         </refsect1>
 552
 553         <refsect1>
 554                 <title>Example 3</title>
 555
 556                 <programlisting># pacstrap -c -d ~/arch-tree/ base
 557 # systemd-nspawn -bD ~/arch-tree/</programlisting>
 558
 559                 <para>This installs a mimimal Arch Linux distribution into
 560                 the directory <filename>~/arch-tree/</filename> and then
 561                 boots an OS in a namespace container in it.</para>
 562         </refsect1>
 563
 564         <refsect1>
 565                 <title>Example 4</title>
 566
 567                 <programlisting># mv ~/arch-tree /var/lib/container/arch
 568 # systemctl enable systemd-nspawn@arch.service
 569 # systemctl start systemd-nspawn@arch.service</programlisting>
 570
 571                 <para>This makes the Arch Linux container part of the
 572                 <filename>multi-user.target</filename> on the host.
 573                 </para>
 574         </refsect1>
 575
 576         <refsect1>
 577                 <title>Example 5</title>
 578
 579                 <programlisting># btrfs subvolume snapshot / /.tmp
 580 # systemd-nspawn --private-network -D /.tmp -b</programlisting>
 581
 582                 <para>This runs a copy of the host system in a
 583                 btrfs snapshot.</para>
 584         </refsect1>
 585
 586         <refsect1>
 587                 <title>Example 6</title>
 588
 589                 <programlisting># chcon system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -R /srv/container
 590 # 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>
 591
 592                 <para>This runs a container with SELinux sandbox security contexts.</para>
 593         </refsect1>
 594
 595         <refsect1>
 596                 <title>Exit status</title>
 597
 598                 <para>The exit code of the program executed in the
 599                 container is returned.</para>
 600         </refsect1>
 601
 602         <refsect1>
 603                 <title>See Also</title>
 604                 <para>
 605                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 606                         <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 607                         <citerefentry><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 608                         <citerefentry><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 609                         <citerefentry><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 610                         <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 611                         <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 612                 </para>
 613         </refsect1>
 614
 615 </refentry>