man/systemd-nspawn.xml

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   6   This file is part of systemd.
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   8   Copyright 2010 Lennart Poettering
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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 <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="opt">COMMAND</arg> <arg choice="opt" rep="repeat">ARGS</arg></command>
  53                 </cmdsynopsis>
  54         </refsynopsisdiv>
  55
  56         <refsect1>
  57                 <title>Description</title>
  58
  59                 <para><command>systemd-nspawn</command> may be used to
  60                 run a command or OS in a light-weight namespace
  61                 container. In many ways it is similar to
  62                 <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
  63                 but more powerful since it fully virtualizes the file
  64                 system hierarchy, as well as the process tree, the
  65                 various IPC subsystems and the host and domain
  66                 name.</para>
  67
  68                 <para><command>systemd-nspawn</command> limits access
  69                 to various kernel interfaces in the container to
  70                 read-only, such as <filename>/sys</filename>,
  71                 <filename>/proc/sys</filename> or
  72                 <filename>/sys/fs/selinux</filename>. Network
  73                 interfaces and the system clock may not be changed
  74                 from within the container. Device nodes may not be
  75                 created. The host system cannot be rebooted and kernel
  76                 modules may not be loaded from within the
  77                 container.</para>
  78
  79                 <para>Note that even though these security precautions
  80                 are taken <command>systemd-nspawn</command> is not
  81                 suitable for secure container setups. Many of the
  82                 security features may be circumvented and are hence
  83                 primarily useful to avoid accidental changes to the
  84                 host system from the container. The intended use of
  85                 this program is debugging and testing as well as
  86                 building of packages, distributions and software
  87                 involved with boot and systems management.</para>
  88
  89                 <para>In contrast to
  90                 <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  91                 <command>systemd-nspawn</command> may be used to boot
  92                 full Linux-based operating systems in a
  93                 container.</para>
  94
  95                 <para>Use a tool like
  96                 <citerefentry><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
  97                 <citerefentry><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  98                 or
  99                 <citerefentry><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 100                 to set up an OS directory tree suitable as file system
 101                 hierarchy for <command>systemd-nspawn</command>
 102                 containers.</para>
 103
 104                 <para>Note that <command>systemd-nspawn</command> will
 105                 mount file systems private to the container to
 106                 <filename>/dev</filename>,
 107                 <filename>/run</filename> and similar. These will
 108                 not be visible outside of the container, and their
 109                 contents will be lost when the container exits.</para>
 110
 111                 <para>Note that running two
 112                 <command>systemd-nspawn</command> containers from the
 113                 same directory tree will not make processes in them
 114                 see each other. The PID namespace separation of the
 115                 two containers is complete and the containers will
 116                 share very few runtime objects except for the
 117                 underlying file system.</para>
 118
 119                 <para><command>systemd-nspawn</command> implements the
 120                 <ulink
 121                 url="http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface">Container
 122                 Interface</ulink> specification.</para>
 123         </refsect1>
 124
 125         <refsect1>
 126                 <title>Options</title>
 127
 128                 <para>If no arguments are passed the container is set
 129                 up and a shell started in it, otherwise the passed
 130                 command and arguments are executed in it. The
 131                 following options are understood:</para>
 132
 133                 <variablelist>
 134                         <varlistentry>
 135                                 <term><option>-h</option></term>
 136                                 <term><option>--help</option></term>
 137
 138                                 <listitem><para>Prints a short help
 139                                 text and exits.</para></listitem>
 140                         </varlistentry>
 141
 142                         <varlistentry>
 143                                 <term><option>--version</option></term>
 144
 145                                 <listitem><para>Prints a version string
 146                                 and exits.</para></listitem>
 147                         </varlistentry>
 148
 149                         <varlistentry>
 150                                 <term><option>-D</option></term>
 151                                 <term><option>--directory=</option></term>
 152
 153                                 <listitem><para>Directory to use as
 154                                 file system root for the namespace
 155                                 container. If omitted the current
 156                                 directory will be
 157                                 used.</para></listitem>
 158                         </varlistentry>
 159
 160                         <varlistentry>
 161                                 <term><option>-b</option></term>
 162                                 <term><option>--boot</option></term>
 163
 164                                 <listitem><para>Automatically search
 165                                 for an init binary and invoke it
 166                                 instead of a shell or a user supplied
 167                                 program.</para></listitem>
 168                         </varlistentry>
 169
 170                         <varlistentry>
 171                                 <term><option>-u</option></term>
 172                                 <term><option>--user=</option></term>
 173
 174                                 <listitem><para>Run the command
 175                                 under specified user, create home
 176                                 directory and cd into it. As rest
 177                                 of systemd-nspawn, this is not
 178                                 the security feature and limits
 179                                 against accidental changes only.
 180                                 </para></listitem>
 181                         </varlistentry>
 182
 183                         <varlistentry>
 184                                 <term><option>--uuid=</option></term>
 185
 186                                 <listitem><para>Set the specified uuid
 187                                 for the container. The init system
 188                                 will initialize
 189                                 <filename>/etc/machine-id</filename>
 190                                 from this if this file is not set yet.
 191                                 </para></listitem>
 192                         </varlistentry>
 193
 194                         <varlistentry>
 195                                 <term><option>-C</option></term>
 196                                 <term><option>--controllers=</option></term>
 197
 198                                 <listitem><para>Makes the container appear in
 199                                 other hierarchies than the name=systemd:/ one.
 200                                 Takes a comma-separated list of controllers.
 201                                 </para></listitem>
 202                         </varlistentry>
 203
 204                         <varlistentry>
 205                                 <term><option>--private-network</option></term>
 206
 207                                 <listitem><para>Turn off networking in
 208                                 the container. This makes all network
 209                                 interfaces unavailable in the
 210                                 container, with the exception of the
 211                                 loopback device.</para></listitem>
 212                         </varlistentry>
 213
 214                         <varlistentry>
 215                                 <term><option>--read-only</option></term>
 216
 217                                 <listitem><para>Mount the root file
 218                                 system read only for the
 219                                 container.</para></listitem>
 220                         </varlistentry>
 221
 222                         <varlistentry>
 223                                 <term><option>--capability=</option></term>
 224
 225                                 <listitem><para>List one or more
 226                                 additional capabilities to grant the
 227                                 container. Takes a comma separated
 228                                 list of capability names, see
 229                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 230                                 for more information. Note that the
 231                                 following capabilities will be granted
 232                                 in any way: CAP_CHOWN,
 233                                 CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH,
 234                                 CAP_FOWNER, CAP_FSETID, CAP_IPC_OWNER,
 235                                 CAP_KILL, CAP_LEASE,
 236                                 CAP_LINUX_IMMUTABLE,
 237                                 CAP_NET_BIND_SERVICE,
 238                                 CAP_NET_BROADCAST, CAP_NET_RAW,
 239                                 CAP_SETGID, CAP_SETFCAP, CAP_SETPCAP,
 240                                 CAP_SETUID, CAP_SYS_ADMIN,
 241                                 CAP_SYS_CHROOT, CAP_SYS_NICE,
 242                                 CAP_SYS_PTRACE, CAP_SYS_TTY_CONFIG,
 243                                 CAP_SYS_RESOURCE, CAP_SYS_BOOT,
 244                                 CAP_AUDIT_WRITE,
 245                                 CAP_AUDIT_CONTROL.</para></listitem>
 246                         </varlistentry>
 247
 248                         <varlistentry>
 249                                 <term><option>--link-journal=</option></term>
 250
 251                                 <listitem><para>Control whether the
 252                                 container's journal shall be made
 253                                 visible to the host system. If enabled
 254                                 allows viewing the container's journal
 255                                 files from the host (but not vice
 256                                 versa). Takes one of
 257                                 <literal>no</literal>,
 258                                 <literal>host</literal>,
 259                                 <literal>guest</literal>,
 260                                 <literal>auto</literal>. If
 261                                 <literal>no</literal>, the journal is
 262                                 not linked. If <literal>host</literal>,
 263                                 the journal files are stored on the
 264                                 host file system (beneath
 265                                 <filename>/var/log/journal/&lt;machine-id&gt;</filename>)
 266                                 and the subdirectory is bind-mounted
 267                                 into the container at the same
 268                                 location. If <literal>guest</literal>,
 269                                 the journal files are stored on the
 270                                 guest file system (beneath
 271                                 <filename>/var/log/journal/&lt;machine-id&gt;</filename>)
 272                                 and the subdirectory is symlinked into the host
 273                                 at the same location. If
 274                                 <literal>auto</literal> (the default),
 275                                 and the right subdirectory of
 276                                 <filename>/var/log/journal</filename>
 277                                 exists, it will be bind mounted
 278                                 into the container. If the
 279                                 subdirectory doesn't exist, no
 280                                 linking is performed. Effectively,
 281                                 booting a container once with
 282                                 <literal>guest</literal> or
 283                                 <literal>host</literal> will link the
 284                                 journal persistently if further on
 285                                 the default of <literal>auto</literal>
 286                                 is used.</para></listitem>
 287                         </varlistentry>
 288
 289                         <varlistentry>
 290                                 <term><option>-j</option></term>
 291
 292                                 <listitem><para>Equivalent to
 293                                 <option>--link-journal=guest</option>.</para></listitem>
 294                         </varlistentry>
 295                 </variablelist>
 296
 297         </refsect1>
 298
 299         <refsect1>
 300                 <title>Example 1</title>
 301
 302                 <programlisting># yum -y --releasever=19 --nogpg --installroot=/srv/mycontainer --disablerepo='*' --enablerepo=fedora install systemd passwd yum fedora-release vim-minimal
 303 # systemd-nspawn -bD /srv/mycontainer</programlisting>
 304
 305                 <para>This installs a minimal Fedora distribution into
 306                 the directory <filename>/srv/mycontainer/</filename> and
 307                 then boots an OS in a namespace container in
 308                 it.</para>
 309         </refsect1>
 310
 311         <refsect1>
 312                 <title>Example 2</title>
 313
 314                 <programlisting># debootstrap --arch=amd64 unstable ~/debian-tree/
 315 # systemd-nspawn -D ~/debian-tree/</programlisting>
 316
 317                 <para>This installs a minimal Debian unstable
 318                 distribution into the directory
 319                 <filename>~/debian-tree/</filename> and then spawns a
 320                 shell in a namespace container in it.</para>
 321
 322         </refsect1>
 323
 324         <refsect1>
 325                 <title>Example 3</title>
 326
 327                 <programlisting># pacstrap -c -d ~/arch-tree/ base
 328 # systemd-nspawn -bD ~/arch-tree/</programlisting>
 329
 330                 <para>This installs a mimimal Arch Linux distribution into
 331                 the directory <filename>~/arch-tree/</filename> and then
 332                 boots an OS in a namespace container in it.</para>
 333         </refsect1>
 334
 335         <refsect1>
 336                 <title>Exit status</title>
 337
 338                 <para>The exit code of the program executed in the
 339                 container is returned.</para>
 340         </refsect1>
 341
 342         <refsect1>
 343                 <title>See Also</title>
 344                 <para>
 345                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 346                         <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 347                         <citerefentry><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 348                         <citerefentry><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 349                         <citerefentry><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 350                 </para>
 351         </refsect1>
 352
 353 </refentry>