man/systemd-nspawn.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3         "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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   6   This file is part of systemd.
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   8   Copyright 2010 Lennart Poettering
   9
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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         </refsect1>
 118
 119         <refsect1>
 120                 <title>Options</title>
 121
 122                 <para>If no arguments are passed the container is set
 123                 up and a shell started in it, otherwise the passed
 124                 command and arguments are executed in it. The
 125                 following options are understood:</para>
 126
 127                 <variablelist>
 128                         <varlistentry>
 129                                 <term><option>--help</option></term>
 130                                 <term><option>-h</option></term>
 131
 132                                 <listitem><para>Prints a short help
 133                                 text and exits.</para></listitem>
 134                         </varlistentry>
 135
 136                         <varlistentry>
 137                                 <term><option>--directory=</option></term>
 138                                 <term><option>-D</option></term>
 139
 140                                 <listitem><para>Directory to use as
 141                                 file system root for the namespace
 142                                 container. If omitted the current
 143                                 directory will be
 144                                 used.</para></listitem>
 145                         </varlistentry>
 146
 147                         <varlistentry>
 148                                 <term><option>--boot</option></term>
 149                                 <term><option>-b</option></term>
 150
 151                                 <listitem><para>Automatically search
 152                                 for an init binary and invoke it
 153                                 instead of a shell or a user supplied
 154                                 program.</para></listitem>
 155                         </varlistentry>
 156
 157                         <varlistentry>
 158                                 <term><option>--user=</option></term>
 159                                 <term><option>-u</option></term>
 160
 161                                 <listitem><para>Run the command
 162                                 under specified user, create home
 163                                 directory and cd into it. As rest
 164                                 of systemd-nspawn, this is not
 165                                 the security feature and limits
 166                                 against accidental changes only.
 167                                 </para></listitem>
 168                         </varlistentry>
 169
 170                         <varlistentry>
 171                                 <term><option>--uuid=</option></term>
 172
 173                                 <listitem><para>Set the specified uuid
 174                                 for the container. The init system
 175                                 will initialize
 176                                 <filename>/etc/machine-id</filename>
 177                                 from this if this file is not set yet.
 178                                 </para></listitem>
 179                         </varlistentry>
 180
 181                         <varlistentry>
 182                                 <term><option>--controllers=</option></term>
 183                                 <term><option>-C</option></term>
 184
 185                                 <listitem><para>Makes the container appear in
 186                                 other hierarchies that the name=systemd:/ one.
 187                                 Takes a comma-separated list of controllers.
 188                                 </para></listitem>
 189                         </varlistentry>
 190
 191                         <varlistentry>
 192                                 <term><option>--private-network</option></term>
 193
 194                                 <listitem><para>Turn off networking in
 195                                 the container. This makes all network
 196                                 interfaces unavailable in the
 197                                 container, with the exception of the
 198                                 loopback device.</para></listitem>
 199                         </varlistentry>
 200
 201                         <varlistentry>
 202                                 <term><option>--read-only</option></term>
 203
 204                                 <listitem><para>Mount the root file
 205                                 system read only for the
 206                                 container.</para></listitem>
 207                         </varlistentry>
 208
 209                 </variablelist>
 210
 211         </refsect1>
 212
 213         <refsect1>
 214                 <title>Example 1</title>
 215
 216                 <programlisting># yum --releasever=17 --nogpgcheck --installroot ~/fedora-tree/ install yum passwd vim-minimal rootfiles systemd
 217 # systemd-nspawn -D ~/fedora-tree /usr/lib/systemd/systemd</programlisting>
 218
 219                 <para>This installs a minimal Fedora distribution into
 220                 the directory <filename>~/fedora-tree/</filename>
 221                 and then boots an OS in a namespace container in it,
 222                 with systemd as init system.</para>
 223         </refsect1>
 224
 225         <refsect1>
 226                 <title>Example 2</title>
 227
 228                 <programlisting># debootstrap --arch=amd64 unstable ~/debian-tree/
 229 # systemd-nspawn -D ~/debian-tree/</programlisting>
 230
 231                 <para>This installs a minimal Debian unstable
 232                 distribution into the directory
 233                 <filename>~/debian-tree/</filename> and then spawns a
 234                 shell in a namespace container in it.</para>
 235
 236         </refsect1>
 237
 238         <refsect1>
 239                 <title>Exit status</title>
 240
 241                 <para>The exit code of the program executed in the
 242                 container is returned.</para>
 243         </refsect1>
 244
 245         <refsect1>
 246                 <title>See Also</title>
 247                 <para>
 248                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 249                         <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 250                         <citerefentry><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 251                         <citerefentry><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 252                 </para>
 253         </refsect1>
 254
 255 </refentry>