man/nss-resolve.xml

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   8   Copyright 2011 Lennart Poettering
   9   Copyright 2013 Tom Gundersen
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  24
  25 <refentry id="nss-resolve" conditional='ENABLE_RESOLVED'>
  26
  27   <refentryinfo>
  28     <title>nss-resolve</title>
  29     <productname>systemd</productname>
  30
  31     <authorgroup>
  32       <author>
  33         <contrib>Developer</contrib>
  34         <firstname>Lennart</firstname>
  35         <surname>Poettering</surname>
  36         <email>lennart@poettering.net</email>
  37       </author>
  38     </authorgroup>
  39   </refentryinfo>
  40
  41   <refmeta>
  42     <refentrytitle>nss-resolve</refentrytitle>
  43     <manvolnum>8</manvolnum>
  44   </refmeta>
  45
  46   <refnamediv>
  47     <refname>nss-resolve</refname>
  48     <refname>libnss_resolve.so.2</refname>
  49     <refpurpose>Provide hostname resolution via <filename>systemd-resolved.service</filename></refpurpose>
  50   </refnamediv>
  51
  52   <refsynopsisdiv>
  53     <para><filename>libnss_resolve.so.2</filename></para>
  54   </refsynopsisdiv>
  55
  56   <refsect1>
  57     <title>Description</title>
  58
  59     <para><command>nss-resolve</command> is a plug-in module for the GNU Name Service Switch (NSS) functionality of the
  60     GNU C Library (<command>glibc</command>) enabling it to resolve host names via the
  61     <citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry> local network
  62     name resolution service. It replaces the <command>nss-dns</command> plug-in module that traditionally resolves
  63     hostnames via DNS.</para>
  64
  65     <para>To activate the NSS module, add <literal>resolve</literal> to the line starting with
  66     <literal>hosts:</literal> in <filename>/etc/nsswitch.conf</filename>. Specifically, it is recommended to place
  67     <literal>resolve</literal> early in <filename>/etc/nsswitch.conf</filename>'s <literal>hosts:</literal> line (but
  68     after the <literal>files</literal> or <literal>mymachines</literal> entries), right before the
  69     <literal>dns</literal> entry if it exists, followed by <literal>[!UNAVAIL=return]</literal>, to ensure DNS queries
  70     are always routed via
  71     <citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry> if it is
  72     running, but are routed to <command>nss-dns</command> if this service is not available.</para>
  73
  74     <para>Note that <command>systemd-resolved</command> will synthesize DNS resource
  75     records in a few cases, for example for the <literal>localhost</literal> and the
  76     current hostname, see
  77     <citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  78     for the full list. This duplicates the functionality of
  79     <citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
  80     but it is still recommended (see examples below) to keep
  81     <command>nss-myhostname</command> configured in
  82     <filename>/etc/nsswitch.conf</filename>, to keep those names resolveable if
  83     <command>systemd-resolved</command> is not running.</para>
  84   </refsect1>
  85
  86   <refsect1>
  87     <title>Example</title>
  88
  89     <para>Here is an example <filename>/etc/nsswitch.conf</filename> file that enables <command>nss-resolve</command>
  90     correctly:</para>
  91
  92 <programlisting>passwd:         compat mymachines systemd
  93 group:          compat mymachines systemd
  94 shadow:         compat
  95
  96 hosts:          files mymachines <command>resolve [!UNAVAIL=return]</command> dns myhostname
  97 networks:       files
  98
  99 protocols:      db files
 100 services:       db files
 101 ethers:         db files
 102 rpc:            db files
 103
 104 netgroup:       nis</programlisting>
 105   </refsect1>
 106
 107   <refsect1>
 108     <title>See Also</title>
 109     <para>
 110       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 111       <citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 112       <citerefentry><refentrytitle>nss-systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 113       <citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 114       <citerefentry><refentrytitle>nss-mymachines</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 115       <citerefentry project='man-pages'><refentrytitle>nsswitch.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 116     </para>
 117   </refsect1>
 118
 119 </refentry>