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 <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                 or
  98                 <citerefentry><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  99                 to set up an OS directory tree suitable as file system
 100                 hierarchy for <command>systemd-nspawn</command>
 101                 containers.</para>
 102
 103                 <para>Note that <command>systemd-nspawn</command> will
 104                 mount file systems private to the container to
 105                 <filename>/dev</filename>,
 106                 <filename>/run</filename> and similar. These will
 107                 not be visible outside of the container, and their
 108                 contents will be lost when the container exits.</para>
 109
 110                 <para>Note that running two
 111                 <command>systemd-nspawn</command> containers from the
 112                 same directory tree will not make processes in them
 113                 see each other. The PID namespace separation of the
 114                 two containers is complete and the containers will
 115                 share very few runtime objects except for the
 116                 underlying file system.</para>
 117
 118                 <para><command>systemd-nspawn</command> implements the
 119                 <ulink
 120                 url="http://www.freedesktop.org/wiki/Software/systemd/ContainerInterface">Container
 121                 Interface</ulink> specification.</para>
 122         </refsect1>
 123
 124         <refsect1>
 125                 <title>Options</title>
 126
 127                 <para>If no arguments are passed the container is set
 128                 up and a shell started in it, otherwise the passed
 129                 command and arguments are executed in it. The
 130                 following options are understood:</para>
 131
 132                 <variablelist>
 133                         <varlistentry>
 134                                 <term><option>--help</option></term>
 135                                 <term><option>-h</option></term>
 136
 137                                 <listitem><para>Prints a short help
 138                                 text and exits.</para></listitem>
 139                         </varlistentry>
 140
 141                         <varlistentry>
 142                                 <term><option>--version</option></term>
 143
 144                                 <listitem><para>Prints a version string
 145                                 and exits.</para></listitem>
 146                         </varlistentry>
 147
 148                         <varlistentry>
 149                                 <term><option>--directory=</option></term>
 150                                 <term><option>-D</option></term>
 151
 152                                 <listitem><para>Directory to use as
 153                                 file system root for the namespace
 154                                 container. If omitted the current
 155                                 directory will be
 156                                 used.</para></listitem>
 157                         </varlistentry>
 158
 159                         <varlistentry>
 160                                 <term><option>--boot</option></term>
 161                                 <term><option>-b</option></term>
 162
 163                                 <listitem><para>Automatically search
 164                                 for an init binary and invoke it
 165                                 instead of a shell or a user supplied
 166                                 program.</para></listitem>
 167                         </varlistentry>
 168
 169                         <varlistentry>
 170                                 <term><option>--user=</option></term>
 171                                 <term><option>-u</option></term>
 172
 173                                 <listitem><para>Run the command
 174                                 under specified user, create home
 175                                 directory and cd into it. As rest
 176                                 of systemd-nspawn, this is not
 177                                 the security feature and limits
 178                                 against accidental changes only.
 179                                 </para></listitem>
 180                         </varlistentry>
 181
 182                         <varlistentry>
 183                                 <term><option>--uuid=</option></term>
 184
 185                                 <listitem><para>Set the specified uuid
 186                                 for the container. The init system
 187                                 will initialize
 188                                 <filename>/etc/machine-id</filename>
 189                                 from this if this file is not set yet.
 190                                 </para></listitem>
 191                         </varlistentry>
 192
 193                         <varlistentry>
 194                                 <term><option>--controllers=</option></term>
 195                                 <term><option>-C</option></term>
 196
 197                                 <listitem><para>Makes the container appear in
 198                                 other hierarchies than the name=systemd:/ one.
 199                                 Takes a comma-separated list of controllers.
 200                                 </para></listitem>
 201                         </varlistentry>
 202
 203                         <varlistentry>
 204                                 <term><option>--private-network</option></term>
 205
 206                                 <listitem><para>Turn off networking in
 207                                 the container. This makes all network
 208                                 interfaces unavailable in the
 209                                 container, with the exception of the
 210                                 loopback device.</para></listitem>
 211                         </varlistentry>
 212
 213                         <varlistentry>
 214                                 <term><option>--read-only</option></term>
 215
 216                                 <listitem><para>Mount the root file
 217                                 system read only for the
 218                                 container.</para></listitem>
 219                         </varlistentry>
 220
 221                         <varlistentry>
 222                                 <term><option>--capability=</option></term>
 223
 224                                 <listitem><para>List one or more
 225                                 additional capabilities to grant the
 226                                 container. Takes a comma separated
 227                                 list of capability names, see
 228                                 <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 229                                 for more information. Note that the
 230                                 following capabilities will be
 231                                 granted in any way: CAP_CHOWN,
 232                                 CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH,
 233                                 CAP_FOWNER, CAP_FSETID, CAP_IPC_OWNER,
 234                                 CAP_KILL, CAP_LEASE,
 235                                 CAP_LINUX_IMMUTABLE,
 236                                 CAP_NET_BIND_SERVICE,
 237                                 CAP_NET_BROADCAST, CAP_NET_RAW,
 238                                 CAP_SETGID, CAP_SETFCAP, CAP_SETPCAP,
 239                                 CAP_SETUID, CAP_SYS_ADMIN,
 240                                 CAP_SYS_CHROOT, CAP_SYS_NICE,
 241                                 CAP_SYS_PTRACE, CAP_SYS_TTY_CONFIG,
 242                                 CAP_SYS_RESOURCE, CAP_SYS_BOOT.</para></listitem>
 243                         </varlistentry>
 244
 245                         <varlistentry>
 246                                 <term><option>--link-journal=</option></term>
 247
 248                                 <listitem><para>Control whether the
 249                                 container's journal shall be made
 250                                 visible to the host system. If enabled
 251                                 allows viewing the container's journal
 252                                 files from the host (but not vice
 253                                 versa). Takes one of
 254                                 <literal>no</literal>,
 255                                 <literal>host</literal>,
 256                                 <literal>guest</literal>,
 257                                 <literal>auto</literal>. If
 258                                 <literal>no</literal>, the journal is
 259                                 not linked. If <literal>host</literal>,
 260                                 the journal files are stored on the
 261                                 host file system (beneath
 262                                 <filename>/var/log/journal/&lt;machine-id&gt;</filename>)
 263                                 and the subdirectory is bind-mounted
 264                                 into the container at the same
 265                                 location. If <literal>guest</literal>,
 266                                 the journal files are stored on the
 267                                 guest file system (beneath
 268                                 <filename>/var/log/journal/&lt;machine-id&gt;</filename>)
 269                                 and the subdirectory is symlinked into the host
 270                                 at the same location. If
 271                                 <literal>auto</literal> (the default),
 272                                 and the right subdirectory of
 273                                 <filename>/var/log/journal</filename>
 274                                 exists, it will be bind mounted
 275                                 into the container. If the
 276                                 subdirectory doesn't exist, no
 277                                 linking is performed. Effectively,
 278                                 booting a container once with
 279                                 <literal>guest</literal> or
 280                                 <literal>host</literal> will link the
 281                                 journal persistently if further on
 282                                 the default of <literal>auto</literal>
 283                                 is used.</para></listitem>
 284                         </varlistentry>
 285
 286                         <varlistentry>
 287                                 <term><option>-j</option></term>
 288
 289                                 <listitem><para>Equivalent to
 290                                 <option>--link-journal=guest</option>.</para></listitem>
 291                         </varlistentry>
 292                 </variablelist>
 293
 294         </refsect1>
 295
 296         <refsect1>
 297                 <title>Example 1</title>
 298
 299                 <programlisting># yum --releasever=17 --nogpgcheck --installroot ~/fedora-tree/ install yum passwd vim-minimal rootfiles systemd
 300 # systemd-nspawn -D ~/fedora-tree /usr/lib/systemd/systemd</programlisting>
 301
 302                 <para>This installs a minimal Fedora distribution into
 303                 the directory <filename>~/fedora-tree/</filename>
 304                 and then boots an OS in a namespace container in it,
 305                 with systemd as init system.</para>
 306         </refsect1>
 307
 308         <refsect1>
 309                 <title>Example 2</title>
 310
 311                 <programlisting># debootstrap --arch=amd64 unstable ~/debian-tree/
 312 # systemd-nspawn -D ~/debian-tree/</programlisting>
 313
 314                 <para>This installs a minimal Debian unstable
 315                 distribution into the directory
 316                 <filename>~/debian-tree/</filename> and then spawns a
 317                 shell in a namespace container in it.</para>
 318
 319         </refsect1>
 320
 321         <refsect1>
 322                 <title>Exit status</title>
 323
 324                 <para>The exit code of the program executed in the
 325                 container is returned.</para>
 326         </refsect1>
 327
 328         <refsect1>
 329                 <title>See Also</title>
 330                 <para>
 331                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 332                         <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 333                         <citerefentry><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 334                         <citerefentry><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 335                 </para>
 336         </refsect1>
 337
 338 </refentry>