X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=blobdiff_plain;f=man%2Fsystemd-nspawn.xml;h=8396def003e59b3b61f793938ec6a7ab0108804b;hb=cb96a2c69;hp=554637d5f1919b0fc223860a3e47fe854c42fffb;hpb=4d62fb4298a5904a53f484636c91540d08f68765;p=elogind.git

diff --git a/man/systemd-nspawn.xml b/man/systemd-nspawn.xml
index 554637d5f..8396def00 100644
--- a/man/systemd-nspawn.xml
+++ b/man/systemd-nspawn.xml
@@ -49,7 +49,10 @@
 
         <refsynopsisdiv>
                 <cmdsynopsis>
-                        <command>systemd-nspawn <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="opt">COMMAND</arg> <arg choice="opt" rep="repeat">ARGS</arg></command>
+                        <command>systemd-nspawn</command>
+                        <arg choice="opt" rep="repeat">OPTIONS</arg>
+                        <arg choice="opt">COMMAND</arg>
+                        <arg choice="opt" rep="repeat">ARGS</arg>
                 </cmdsynopsis>
         </refsynopsisdiv>
 
@@ -114,7 +117,10 @@
                 see each other. The PID namespace separation of the
                 two containers is complete and the containers will
                 share very few runtime objects except for the
-                underlying file system.</para>
+                underlying file system. It is however possible to
+                enter an existing container, see
+                <link linkend='example-nsenter'>Example 4</link> below.
+                </para>
 
                 <para><command>systemd-nspawn</command> implements the
                 <ulink
@@ -132,8 +138,8 @@
 
                 <variablelist>
                         <varlistentry>
-                                <term><option>--help</option></term>
                                 <term><option>-h</option></term>
+                                <term><option>--help</option></term>
 
                                 <listitem><para>Prints a short help
                                 text and exits.</para></listitem>
@@ -147,8 +153,8 @@
                         </varlistentry>
 
                         <varlistentry>
-                                <term><option>--directory=</option></term>
                                 <term><option>-D</option></term>
+                                <term><option>--directory=</option></term>
 
                                 <listitem><para>Directory to use as
                                 file system root for the namespace
@@ -158,18 +164,20 @@
                         </varlistentry>
 
                         <varlistentry>
-                                <term><option>--boot</option></term>
                                 <term><option>-b</option></term>
+                                <term><option>--boot</option></term>
 
                                 <listitem><para>Automatically search
                                 for an init binary and invoke it
                                 instead of a shell or a user supplied
-                                program.</para></listitem>
+                                program. A command to execute cannot
+                                be specified in this case.
+                                </para></listitem>
                         </varlistentry>
 
                         <varlistentry>
-                                <term><option>--user=</option></term>
                                 <term><option>-u</option></term>
+                                <term><option>--user=</option></term>
 
                                 <listitem><para>Run the command
                                 under specified user, create home
@@ -192,8 +200,8 @@
                         </varlistentry>
 
                         <varlistentry>
-                                <term><option>--controllers=</option></term>
                                 <term><option>-C</option></term>
+                                <term><option>--controllers=</option></term>
 
                                 <listitem><para>Makes the container appear in
                                 other hierarchies than the name=systemd:/ one.
@@ -262,13 +270,13 @@
                                 not linked. If <literal>host</literal>,
                                 the journal files are stored on the
                                 host file system (beneath
-                                <filename>/var/log/journal/&lt;machine-id&gt;</filename>)
+                                <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
                                 and the subdirectory is bind-mounted
                                 into the container at the same
                                 location. If <literal>guest</literal>,
                                 the journal files are stored on the
                                 guest file system (beneath
-                                <filename>/var/log/journal/&lt;machine-id&gt;</filename>)
+                                <filename>/var/log/journal/<replaceable>machine-id</replaceable></filename>)
                                 and the subdirectory is symlinked into the host
                                 at the same location. If
                                 <literal>auto</literal> (the default),
@@ -318,7 +326,6 @@
                 distribution into the directory
                 <filename>~/debian-tree/</filename> and then spawns a
                 shell in a namespace container in it.</para>
-
         </refsect1>
 
         <refsect1>
@@ -332,6 +339,24 @@
                 boots an OS in a namespace container in it.</para>
         </refsect1>
 
+        <refsect1 id='example-nsenter'>
+                <title>Example 4</title>
+
+                <para>To enter the container, PID of one of the
+                processes sharing the new namespaces must be used.
+                <command>systemd-nspawn</command> prints the PID
+                (as viewed from the outside) of the launched process,
+                and it can be used to enter the container.</para>
+
+                <programlisting># nsenter -muinpt $PID</programlisting>
+
+                <para><citerefentry><refentrytitle>nsenter</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+                is part of
+                <ulink url="https://github.com/karelzak/util-linux">util-linux</ulink>.
+                Kernel support for entering namespaces was added in
+                Linux 3.8.</para>
+        </refsect1>
+
         <refsect1>
                 <title>Exit status</title>
 
@@ -344,6 +369,7 @@
                 <para>
                         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                         <citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+                        <citerefentry><refentrytitle>unshare</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                         <citerefentry><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
                         <citerefentry><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
                         <citerefentry><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>