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>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry> or <citerefentry><refentrytitle>mock</refentrytitle><manvolnum>1</manvolnum></citerefentry>
  97                 to set up an OS directory tree suitable as file system
  98                 hierarchy for <command>systemd-nspawn</command> containers.</para>
  99
 100                 <para>Note that <command>systemd-nspawn</command> will
 101                 mount file systems private to the container to
 102                 <filename>/dev</filename>,
 103                 <filename>/run</filename> and similar. These will
 104                 not be visible outside of the container, and their
 105                 contents will be lost when the container exits.</para>
 106
 107                 <para>Note that running two
 108                 <command>systemd-nspawn</command> containers from the
 109                 same directory tree will not make processes in them
 110                 see each other. The PID namespace separation of the
 111                 two containers is complete and the containers will
 112                 share very few runtime objects except for the
 113                 underlying file system.</para>
 114         </refsect1>
 115
 116         <refsect1>
 117                 <title>Options</title>
 118
 119                 <para>If no arguments are passed the container is set
 120                 up and a shell started in it, otherwise the passed
 121                 command and arguments are executed in it. The
 122                 following options are understood:</para>
 123
 124                 <variablelist>
 125                         <varlistentry>
 126                                 <term><option>--help</option></term>
 127                                 <term><option>-h</option></term>
 128
 129                                 <listitem><para>Prints a short help
 130                                 text and exits.</para></listitem>
 131                         </varlistentry>
 132
 133                         <varlistentry>
 134                                 <term><option>--directory=</option></term>
 135                                 <term><option>-D</option></term>
 136
 137                                 <listitem><para>Directory to use as
 138                                 file system root for the namespace
 139                                 container. If omitted the current
 140                                 directory will be
 141                                 used.</para></listitem>
 142                         </varlistentry>
 143
 144                         <varlistentry>
 145                                 <term><option>--user=</option></term>
 146                                 <term><option>-u</option></term>
 147
 148                                 <listitem><para>Run the command
 149                                 under specified user, create home
 150                                 directory and cd into it. As rest
 151                                 of systemd-nspawn, this is not
 152                                 the security feature and limits
 153                                 against accidental changes only.
 154                                 </para></listitem>
 155                         </varlistentry>
 156
 157                         <varlistentry>
 158                                 <term><option>--private-network</option></term>
 159
 160                                 <listitem><para>Turn off networking in
 161                                 the container. This makes all network
 162                                 interfaces unavailable in the
 163                                 container, with the exception of the
 164                                 loopback device.</para></listitem>
 165                         </varlistentry>
 166
 167                 </variablelist>
 168
 169         </refsect1>
 170
 171         <refsect1>
 172                 <title>Example 1</title>
 173
 174                 <programlisting># debootstrap --arch=amd64 unstable debian-tree/
 175 # systemd-nspawn -D debian-tree/</programlisting>
 176
 177                 <para>This installs a minimal Debian unstable
 178                 distribution into the directory
 179                 <filename>debian-tree/</filename> and then spawns a
 180                 shell in a namespace container in it.</para>
 181
 182         </refsect1>
 183
 184         <refsect1>
 185                 <title>Example 2</title>
 186
 187                 <programlisting># mock --init
 188 # systemd-nspawn -D /var/lib/mock/fedora-rawhide-x86_64/root/ /sbin/init systemd.log_level=debug</programlisting>
 189
 190                 <para>This installs a minimal Fedora distribution into
 191                 a subdirectory of <filename>/var/lib/mock/</filename>
 192                 and then boots an OS in a namespace container in it,
 193                 with systemd as init system, configured for debug
 194                 logging.</para>
 195
 196         </refsect1>
 197
 198         <refsect1>
 199                 <title>Exit status</title>
 200
 201                 <para>The exit code of the program executed in the
 202                 container is returned.</para>
 203         </refsect1>
 204
 205         <refsect1>
 206                 <title>See Also</title>
 207                 <para>
 208                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 209                         <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 210                         <citerefentry><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 211                         <citerefentry><refentrytitle>mock</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 212                 </para>
 213         </refsect1>
 214
 215 </refentry>