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>Provide hostname resolution for local
  22     container instances.</refpurpose>
  23   </refnamediv>
  24
  25   <refsynopsisdiv>
  26     <para><filename>libnss_mymachines.so.2</filename></para>
  27   </refsynopsisdiv>
  28
  29   <refsect1>
  30     <title>Description</title>
  31
  32     <para><command>nss-mymachines</command> is a plug-in module for the GNU Name Service Switch (NSS) functionality of
  33     the GNU C Library (<command>glibc</command>), providing hostname resolution for the names of containers running
  34     locally that are registered with
  35     <citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>. The
  36     container names are resolved to the IP addresses of the specific container, ordered by their scope. This
  37     functionality only applies to containers using network namespacing (see the description of
  38     <option>--private-network</option> in
  39     <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>).
  40     Note that the name that is resolved is the one registered with <command>systemd-machined</command>, which
  41     may be different than the hostname configured inside of the container.</para>
  42
  43     <para>The module also provides name resolution for user and group identifiers mapped to containers. All names from
  44     the range allocated to a given container <replaceable>container</replaceable> are exposed on the host as
  45     <literal>vu-<replaceable>container</replaceable>-<replaceable>uid</replaceable></literal> and
  46     <literal>vg-<replaceable>container</replaceable>-<replaceable>gid</replaceable></literal> (see example below). This
  47     functionality only applies to containers using user namespacing (see the description of
  48     <option>--private-users</option> in
  49     <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>).</para>
  50
  51     <para>To activate the NSS module, add <literal>mymachines</literal> to the lines starting with
  52     <literal>hosts:</literal>, <literal>passwd:</literal> and <literal>group:</literal> in
  53     <filename>/etc/nsswitch.conf</filename>.</para>
  54
  55     <para>It is recommended to place <literal>mymachines</literal> after the <literal>files</literal> or
  56     <literal>compat</literal> entry of the <filename>/etc/nsswitch.conf</filename> lines to make sure that its mappings
  57     are preferred over other resolvers such as DNS, but so that <filename>/etc/hosts</filename>,
  58     <filename>/etc/passwd</filename> and <filename>/etc/group</filename> based mappings take precedence.</para>
  59   </refsect1>
  60
  61   <refsect1>
  62     <title>Configuration in <filename>/etc/nsswitch.conf</filename></title>
  63
  64     <para>Here is an example <filename>/etc/nsswitch.conf</filename> file that enables
  65     <command>nss-mymachines</command> correctly:</para>
  66
  67     <!-- synchronize with other nss-* man pages and factory/etc/nsswitch.conf -->
  68     <programlisting>passwd:         compat <command>mymachines</command> systemd
  69 group:          compat <command>mymachines</command> systemd
  70 shadow:         compat
  71
  72 hosts:          files <command>mymachines</command> resolve [!UNAVAIL=return] dns myhostname
  73 networks:       files
  74
  75 protocols:      db files
  76 services:       db files
  77 ethers:         db files
  78 rpc:            db files
  79
  80 netgroup:       nis</programlisting>
  81
  82   </refsect1>
  83
  84   <refsect1>
  85     <title>Mappings provided by <filename>nss-mymachines</filename></title>
  86
  87     <para>The container <literal>rawhide</literal> is spawned using
  88     <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>:
  89     </para>
  90
  91     <programlisting># systemd-nspawn -M rawhide --boot --network-veth --private-users=pick
  92 Spawning container rawhide on /var/lib/machines/rawhide.
  93 Selected user namespace base 20119552 and range 65536.
  94 ...
  95
  96 $ machinectl --max-addresses=3
  97 MACHINE CLASS     SERVICE        OS     VERSION ADDRESSES
  98 rawhide container systemd-nspawn fedora 30      169.254.40.164 fe80::94aa:3aff:fe7b:d4b9
  99
 100 $ getent passwd vu-rawhide-0 vu-rawhide-81
 101 vu-rawhide-0:*:20119552:65534:vu-rawhide-0:/:/sbin/nologin
 102 vu-rawhide-81:*:20119633:65534:vu-rawhide-81:/:/sbin/nologin
 103
 104 $ getent group vg-rawhide-0 vg-rawhide-81
 105 vg-rawhide-0:*:20119552:
 106 vg-rawhide-81:*:20119633:
 107
 108 $ ps -o user:15,pid,tty,command -e|grep '^vu-rawhide'
 109 vu-rawhide-0      692 ?        /usr/lib/systemd/systemd
 110 vu-rawhide-0      731 ?        /usr/lib/systemd/systemd-journald
 111 vu-rawhide-192    734 ?        /usr/lib/systemd/systemd-networkd
 112 vu-rawhide-193    738 ?        /usr/lib/systemd/systemd-resolved
 113 vu-rawhide-0      742 ?        /usr/lib/systemd/systemd-logind
 114 vu-rawhide-81     744 ?        /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only
 115 vu-rawhide-0      746 ?        /usr/sbin/sshd -D ...
 116 vu-rawhide-0      752 ?        /usr/lib/systemd/systemd --user
 117 vu-rawhide-0      753 ?        (sd-pam)
 118 vu-rawhide-0     1628 ?        login -- zbyszek
 119 vu-rawhide-1000  1630 ?        /usr/lib/systemd/systemd --user
 120 vu-rawhide-1000  1631 ?        (sd-pam)
 121 vu-rawhide-1000  1637 pts/8    -zsh
 122
 123 $ ping -c1 rawhide
 124 PING rawhide(fe80::94aa:3aff:fe7b:d4b9%ve-rawhide (fe80::94aa:3aff:fe7b:d4b9%ve-rawhide)) 56 data bytes
 125 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
 126 ...
 127 $ ping -c1 -4 rawhide
 128 PING rawhide (169.254.40.164) 56(84) bytes of data.
 129 64 bytes from 169.254.40.164 (169.254.40.164): icmp_seq=1 ttl=64 time=0.064 ms
 130 ...
 131
 132 # machinectl shell rawhide /sbin/ip a
 133 Connected to machine rawhide. Press ^] three times within 1s to exit session.
 134 1: lo: &lt;LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
 135     ...
 136 2: host0@if21: &lt;BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
 137     link/ether 96:aa:3a:7b:d4:b9 brd ff:ff:ff:ff:ff:ff link-netnsid 0
 138     inet 169.254.40.164/16 brd 169.254.255.255 scope link host0
 139        valid_lft forever preferred_lft forever
 140     inet6 fe80::94aa:3aff:fe7b:d4b9/64 scope link
 141        valid_lft forever preferred_lft forever
 142 Connection to machine rawhide terminated.
 143 </programlisting>
 144   </refsect1>
 145
 146   <refsect1>
 147     <title>See Also</title>
 148     <para>
 149       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 150       <citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 151       <citerefentry><refentrytitle>machinectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 152       <citerefentry><refentrytitle>nss-systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 153       <citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 154       <citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 155       <citerefentry project='man-pages'><refentrytitle>nsswitch.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 156       <citerefentry project='man-pages'><refentrytitle>getent</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 157     </para>
 158   </refsect1>
 159
 160 </refentry>