man/nss-mymachines.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="nss-mymachines" conditional='ENABLE_NSS_MYMACHINES'>
   7
   8   <refentryinfo>
   9     <title>nss-mymachines</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>nss-mymachines</refentrytitle>
  15     <manvolnum>8</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>nss-mymachines</refname>
  20     <refname>libnss_mymachines.so.2</refname>
  21     <refpurpose>Hostname resolution for local container instances</refpurpose>
  22   </refnamediv>
  23
  24   <refsynopsisdiv>
  25     <para><filename>libnss_mymachines.so.2</filename></para>
  26   </refsynopsisdiv>
  27
  28   <refsect1>
  29     <title>Description</title>
  30
  31     <para><command>nss-mymachines</command> is a plug-in module for the GNU Name Service Switch (NSS) functionality of
  32     the GNU C Library (<command>glibc</command>), providing hostname resolution for the names of containers running
  33     locally that are registered with
  34     <citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>. The
  35     container names are resolved to the IP addresses of the specific container, ordered by their scope. This
  36     functionality only applies to containers using network namespacing (see the description of
  37     <option>--private-network</option> in
  38     <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>).
  39     Note that the name that is resolved is the one registered with <command>systemd-machined</command>, which
  40     may be different than the hostname configured inside of the container.</para>
  41
  42     <para>To activate the NSS module, add <literal>mymachines</literal> to the line starting with
  43     <literal>hosts:</literal> in <filename>/etc/nsswitch.conf</filename>.</para>
  44
  45     <para>It is recommended to place <literal>mymachines</literal> after the <literal>files</literal> or
  46     <literal>compat</literal> entry of the <filename>/etc/nsswitch.conf</filename> line to make sure that its
  47     mappings are preferred over other resolvers such as DNS, but so that <filename>/etc/hosts</filename>
  48     based mappings take precedence.</para>
  49   </refsect1>
  50
  51   <refsect1>
  52     <title>Configuration in <filename>/etc/nsswitch.conf</filename></title>
  53
  54     <para>Here is an example <filename>/etc/nsswitch.conf</filename> file that enables
  55     <command>nss-mymachines</command> correctly:</para>
  56
  57     <!-- synchronize with other nss-* man pages and factory/etc/nsswitch.conf -->
  58     <programlisting>passwd:         compat systemd
  59 group:          compat systemd
  60 shadow:         compat
  61
  62 hosts:          <command>mymachines</command> resolve [!UNAVAIL=return] myhostname files dns
  63 networks:       files
  64
  65 protocols:      db files
  66 services:       db files
  67 ethers:         db files
  68 rpc:            db files
  69
  70 netgroup:       nis</programlisting>
  71
  72   </refsect1>
  73
  74   <refsect1>
  75     <title>Example: Mappings provided by <filename>nss-mymachines</filename></title>
  76
  77     <para>The container <literal>rawhide</literal> is spawned using
  78     <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>:
  79     </para>
  80
  81     <programlisting># systemd-nspawn -M rawhide --boot --network-veth --private-users=pick
  82 Spawning container rawhide on /var/lib/machines/rawhide.
  83 Selected user namespace base 20119552 and range 65536.
  84 ...
  85
  86 $ machinectl --max-addresses=3
  87 MACHINE CLASS     SERVICE        OS     VERSION ADDRESSES
  88 rawhide container systemd-nspawn fedora 30      169.254.40.164 fe80::94aa:3aff:fe7b:d4b9
  89
  90 $ ping -c1 rawhide
  91 PING rawhide(fe80::94aa:3aff:fe7b:d4b9%ve-rawhide (fe80::94aa:3aff:fe7b:d4b9%ve-rawhide)) 56 data bytes
  92 64 bytes from fe80::94aa:3aff:fe7b:d4b9%ve-rawhide (fe80::94aa:3aff:fe7b:d4b9%ve-rawhide): icmp_seq=1 ttl=64 time=0.045 ms
  93 ...
  94 $ ping -c1 -4 rawhide
  95 PING rawhide (169.254.40.164) 56(84) bytes of data.
  96 64 bytes from 169.254.40.164 (169.254.40.164): icmp_seq=1 ttl=64 time=0.064 ms
  97 ...
  98
  99 # machinectl shell rawhide /sbin/ip a
 100 Connected to machine rawhide. Press ^] three times within 1s to exit session.
 101 1: lo: &lt;LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
 102     ...
 103 2: host0@if21: &lt;BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
 104     link/ether 96:aa:3a:7b:d4:b9 brd ff:ff:ff:ff:ff:ff link-netnsid 0
 105     inet 169.254.40.164/16 brd 169.254.255.255 scope link host0
 106        valid_lft forever preferred_lft forever
 107     inet6 fe80::94aa:3aff:fe7b:d4b9/64 scope link
 108        valid_lft forever preferred_lft forever
 109 Connection to machine rawhide terminated.
 110 </programlisting>
 111   </refsect1>
 112
 113   <refsect1>
 114     <title>See Also</title>
 115     <para>
 116       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 117       <citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 118       <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 119       <citerefentry><refentrytitle>nss-systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 120       <citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 121       <citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 122       <citerefentry project='man-pages'><refentrytitle>nsswitch.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 123       <citerefentry project='man-pages'><refentrytitle>getent</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 124     </para>
 125   </refsect1>
 126
 127 </refentry>