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
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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>Incompatibility with Auditing</title>
 148
 149                 <para>Note that the kernel auditing subsystem is
 150                 currently broken when used together with
 151                 containers. We hence recommend turning it off entirely
 152                 by booting with <literal>audit=0</literal> on the
 153                 kernel command line, or by turning it off at kernel
 154                 build time. If auditing is enabled in the kernel,
 155                 operating systems booted in an nspawn container might
 156                 refuse log-in attempts.</para>
 157         </refsect1>
 158
 159         <refsect1>
 160                 <title>Options</title>
 161
 162                 <para>If option <option>-b</option> is specified, the
 163                 arguments are used as arguments for the init
 164                 binary. Otherwise, <replaceable>COMMAND</replaceable>
 165                 specifies the program to launch in the container, and
 166                 the remaining arguments are used as arguments for this
 167                 program. If <option>-b</option> is not used and no
 168                 arguments are specifed, a shell is launched in the
 169                 container.</para>
 170
 171                 <para>The following options are understood:</para>
 172
 173                 <variablelist>
 174                         <varlistentry>
 175                                 <term><option>-h</option></term>
 176                                 <term><option>--help</option></term>
 177
 178                                 <listitem><para>Prints a short help
 179                                 text and exits.</para></listitem>
 180                         </varlistentry>
 181
 182                         <varlistentry>
 183                                 <term><option>--version</option></term>
 184
 185                                 <listitem><para>Prints a version string
 186                                 and exits.</para></listitem>
 187                         </varlistentry>
 188
 189                         <varlistentry>
 190                                 <term><option>-D</option></term>
 191                                 <term><option>--directory=</option></term>
 192
 193                                 <listitem><para>Directory to use as
 194                                 file system root for the namespace
 195                                 container. If omitted, the current
 196                                 directory will be
 197                                 used.</para></listitem>
 198                         </varlistentry>
 199
 200                         <varlistentry>
 201                                 <term><option>-b</option></term>
 202                                 <term><option>--boot</option></term>
 203
 204                                 <listitem><para>Automatically search
 205                                 for an init binary and invoke it
 206                                 instead of a shell or a user supplied
 207                                 program. If this option is used,
 208                                 arguments specified on the command
 209                                 line are used as arguments for the
 210                                 init binary. This option may not be
 211                                 combined with
 212                                 <option>--share-system</option>.
 213                                 </para></listitem>
 214                         </varlistentry>
 215
 216                         <varlistentry>
 217                                 <term><option>-u</option></term>
 218                                 <term><option>--user=</option></term>
 219
 220                                 <listitem><para>Run the command
 221                                 under specified user, create home
 222                                 directory and cd into it. As rest
 223                                 of systemd-nspawn, this is not
 224                                 the security feature and limits
 225                                 against accidental changes only.
 226                                 </para></listitem>
 227                         </varlistentry>
 228
 229                         <varlistentry>
 230                                 <term><option>-M</option></term>
 231                                 <term><option>--machine=</option></term>
 232
 233                                 <listitem><para>Sets the machine name
 234                                 for this container. This name may be
 235                                 used to identify this container on the
 236                                 host, and is used to initialize the
 237                                 container's hostname (which the
 238                                 container can choose to override,
 239                                 however). If not specified, the last
 240                                 component of the root directory of the
 241                                 container is used.</para></listitem>
 242                         </varlistentry>
 243
 244                         <varlistentry>
 245                                 <term><option>--slice=</option></term>
 246
 247                                 <listitem><para>Make the container
 248                                 part of the specified slice, instead
 249                                 of the
 250                                 <filename>machine.slice</filename>.</para>
 251                                 </listitem>
 252                         </varlistentry>
 253
 254                         <varlistentry>
 255                                 <term><option>-Z</option></term>
 256                                 <term><option>--selinux-context=</option></term>
 257
 258                                 <listitem><para>Sets the SELinux
 259                                 security context to be used to label
 260                                 processes in the container.</para>
 261                                 </listitem>
 262                         </varlistentry>
 263
 264                         <varlistentry>
 265                                 <term><option>-L</option></term>
 266                                 <term><option>--selinux-apifs-context=</option></term>
 267
 268                                 <listitem><para>Sets the SELinux security
 269                                 context to be used to label files in
 270                                 the virtual API file systems in the
 271                                 container.</para>
 272                                 </listitem>
 273                         </varlistentry>
 274
 275                         <varlistentry>
 276                                 <term><option>--uuid=</option></term>
 277
 278                                 <listitem><para>Set the specified UUID
 279                                 for the container. The init system
 280                                 will initialize
 281                                 <filename>/etc/machine-id</filename>
 282                                 from this if this file is not set yet.
 283                                 </para></listitem>
 284                         </varlistentry>
 285
 286                         <varlistentry>
 287                                 <term><option>--private-network</option></term>
 288
 289                                 <listitem><para>Turn off networking in
 290                                 the container. This makes all network
 291                                 interfaces unavailable in the
 292                                 container, with the exception of the
 293                                 loopback device.</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,
 327                                 CAP_AUDIT_CONTROL.</para></listitem>
 328                         </varlistentry>
 329
 330                         <varlistentry>
 331                                 <term><option>--drop-capability=</option></term>
 332
 333                                 <listitem><para>Specify one or more
 334                                 additional capabilities to drop for
 335                                 the container. This allows running the
 336                                 container with fewer capabilities than
 337                                 the default (see above).</para></listitem>
 338                         </varlistentry>
 339
 340                         <varlistentry>
 341                                 <term><option>--link-journal=</option></term>
 342
 343                                 <listitem><para>Control whether the
 344                                 container's journal shall be made
 345                                 visible to the host system. If enabled,
 346                                 allows viewing the container's journal
 347                                 files from the host (but not vice
 348                                 versa). Takes one of
 349                                 <literal>no</literal>,
 350                                 <literal>host</literal>,
 351                                 <literal>guest</literal>,
 352                                 <literal>auto</literal>. If
 353                                 <literal>no</literal>, the journal is
 354                                 not linked. If <literal>host</literal>,
 355                                 the journal files are stored on the
 356                                 host file system (beneath
 357                                 <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
 358                                 and the subdirectory is bind-mounted
 359                                 into the container at the same
 360                                 location. If <literal>guest</literal>,
 361                                 the journal files are stored on the
 362                                 guest file system (beneath
 363                                 <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
 364                                 and the subdirectory is symlinked into the host
 365                                 at the same location. If
 366                                 <literal>auto</literal> (the default),
 367                                 and the right subdirectory of
 368                                 <filename>/var/log/journal</filename>
 369                                 exists, it will be bind mounted
 370                                 into the container. If the
 371                                 subdirectory does not exist, no
 372                                 linking is performed. Effectively,
 373                                 booting a container once with
 374                                 <literal>guest</literal> or
 375                                 <literal>host</literal> will link the
 376                                 journal persistently if further on
 377                                 the default of <literal>auto</literal>
 378                                 is used.</para></listitem>
 379                         </varlistentry>
 380
 381                         <varlistentry>
 382                                 <term><option>-j</option></term>
 383
 384                                 <listitem><para>Equivalent to
 385                                 <option>--link-journal=guest</option>.</para></listitem>
 386                         </varlistentry>
 387
 388                         <varlistentry>
 389                                 <term><option>--bind=</option></term>
 390                                 <term><option>--bind-ro=</option></term>
 391
 392                                 <listitem><para>Bind mount a file or
 393                                 directory from the host into the
 394                                 container. Either takes a path
 395                                 argument -- in which case the
 396                                 specified path will be mounted from
 397                                 the host to the same path in the
 398                                 container --, or a colon-separated
 399                                 pair of paths -- in which case the
 400                                 first specified path is the source in
 401                                 the host, and the second path is the
 402                                 destination in the container. The
 403                                 <option>--bind-ro=</option> option
 404                                 creates read-only bind
 405                                 mount.</para></listitem>
 406                         </varlistentry>
 407
 408                         <varlistentry>
 409                                 <term><option>--setenv=</option></term>
 410
 411                                 <listitem><para>Specifies an
 412                                 environment variable assignment to
 413                                 pass to the init process in the
 414                                 container, in the format
 415                                 <literal>NAME=VALUE</literal>. This
 416                                 may be used to override the default
 417                                 variables or to set additional
 418                                 variables. This parameter may be used
 419                                 more than once.</para></listitem>
 420                         </varlistentry>
 421
 422                         <varlistentry>
 423                                 <term><option>-q</option></term>
 424                                 <term><option>--quiet</option></term>
 425
 426                                 <listitem><para>Turns off any status
 427                                 output by the tool itself. When this
 428                                 switch is used, then the only output
 429                                 by nspawn will be the console output
 430                                 of the container OS itself.</para></listitem>
 431                         </varlistentry>
 432
 433                         <varlistentry>
 434                                 <term><option>--share-system</option></term>
 435
 436                                 <listitem><para>Allows the container
 437                                 to share certain system facilities
 438                                 with the host. More specifically, this
 439                                 turns off PID namespacing, UTS
 440                                 namespacing and IPC namespacing, and
 441                                 thus allows the guest to see and
 442                                 interact more easily with processes
 443                                 outside of the container. Note that
 444                                 using this option makes it impossible
 445                                 to start up a full Operating System in
 446                                 the container, as an init system
 447                                 cannot operate in this mode. It is
 448                                 only useful to run specific programs
 449                                 or applications this way, without
 450                                 involving an init system in the
 451                                 container. This option implies
 452                                 <option>--register=no</option>. This
 453                                 option may not be combined with
 454                                 <option>--boot</option>.</para></listitem>
 455                         </varlistentry>
 456
 457                         <varlistentry>
 458                                 <term><option>--register=</option></term>
 459
 460                                 <listitem><para>Controls whether the
 461                                 container is registered with
 462                                 <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry>. Takes
 463                                 a boolean argument, defaults to
 464                                 <literal>yes</literal>. This option
 465                                 should be enabled when the container
 466                                 runs a full Operating System (more
 467                                 specifically: an init system), and is
 468                                 useful to ensure the container is
 469                                 accesible via
 470                                 <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 471                                 and shown by tools such as
 472                                 <citerefentry><refentrytitle>ps</refentrytitle><manvolnum>1</manvolnum></citerefentry>. If
 473                                 the container does not run an init
 474                                 system it is recommended to set this
 475                                 option to <literal>no</literal>. Note
 476                                 that <option>--share-system</option>
 477                                 implies
 478                                 <option>--register=no</option>.
 479                                 </para></listitem>
 480                         </varlistentry>
 481                 </variablelist>
 482
 483         </refsect1>
 484
 485         <refsect1>
 486                 <title>Example 1</title>
 487
 488                 <programlisting># yum -y --releasever=19 --nogpg --installroot=/srv/mycontainer --disablerepo='*' --enablerepo=fedora install systemd passwd yum fedora-release vim-minimal
 489 # systemd-nspawn -bD /srv/mycontainer</programlisting>
 490
 491                 <para>This installs a minimal Fedora distribution into
 492                 the directory <filename noindex='true'>/srv/mycontainer/</filename> and
 493                 then boots an OS in a namespace container in
 494                 it.</para>
 495         </refsect1>
 496
 497         <refsect1>
 498                 <title>Example 2</title>
 499
 500                 <programlisting># debootstrap --arch=amd64 unstable ~/debian-tree/
 501 # systemd-nspawn -D ~/debian-tree/</programlisting>
 502
 503                 <para>This installs a minimal Debian unstable
 504                 distribution into the directory
 505                 <filename>~/debian-tree/</filename> and then spawns a
 506                 shell in a namespace container in it.</para>
 507         </refsect1>
 508
 509         <refsect1>
 510                 <title>Example 3</title>
 511
 512                 <programlisting># pacstrap -c -d ~/arch-tree/ base
 513 # systemd-nspawn -bD ~/arch-tree/</programlisting>
 514
 515                 <para>This installs a mimimal Arch Linux distribution into
 516                 the directory <filename>~/arch-tree/</filename> and then
 517                 boots an OS in a namespace container in it.</para>
 518         </refsect1>
 519
 520         <refsect1>
 521                 <title>Example 4</title>
 522
 523                 <programlisting># mv ~/arch-tree /var/lib/container/arch
 524 # systemctl enable systemd-nspawn@arch.service
 525 # systemctl start systemd-nspawn@arch.service</programlisting>
 526
 527                 <para>This makes the Arch Linux container part of the
 528                 <filename>multi-user.target</filename> on the host.
 529                 </para>
 530         </refsect1>
 531
 532         <refsect1>
 533                 <title>Example 5</title>
 534
 535                 <programlisting># btrfs subvolume snapshot / /.tmp
 536 # systemd-nspawn --private-network -D /.tmp -b</programlisting>
 537
 538                 <para>This runs a copy of the host system in a
 539                 btrfs snapshot.</para>
 540         </refsect1>
 541
 542         <refsect1>
 543                 <title>Example 6</title>
 544
 545                 <programlisting># chcon system_u:object_r:svirt_sandbox_file_t:s0:c0,c1 -R /srv/container
 546 # 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>
 547
 548                 <para>This runs a container with SELinux sandbox security contexts.</para>
 549         </refsect1>
 550
 551         <refsect1>
 552                 <title>Exit status</title>
 553
 554                 <para>The exit code of the program executed in the
 555                 container is returned.</para>
 556         </refsect1>
 557
 558         <refsect1>
 559                 <title>See Also</title>
 560                 <para>
 561                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 562                         <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 563                         <citerefentry><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 564                         <citerefentry><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 565                         <citerefentry><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 566                         <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 567                         <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 568                 </para>
 569         </refsect1>
 570
 571 </refentry>