man/nss-myhostname.html

   1 <html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>nss-myhostname</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><style>
   2     a.headerlink {
   3       color: #c60f0f;
   4       font-size: 0.8em;
   5       padding: 0 4px 0 4px;
   6       text-decoration: none;
   7       visibility: hidden;
   8     }
   9
  10     a.headerlink:hover {
  11       background-color: #c60f0f;
  12       color: white;
  13     }
  14
  15     h1:hover > a.headerlink, h2:hover > a.headerlink, h3:hover > a.headerlink, dt:hover > a.headerlink {
  16       visibility: visible;
  17     }
  18   </style><a href="index.html">Index </a>·
  19   <a href="systemd.directives.html">Directives </a>·
  20   <a href="../python-systemd/index.html">Python </a>·
  21   <a href="../libudev/index.html">libudev </a>·
  22   <a href="../libudev/index.html">gudev </a><span style="float:right">systemd 204</span><hr><div class="refentry"><a name="nss-myhostname"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nss-myhostname — Provide host name resolution for the locally
  23                 configured system hostname.</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><p><code class="filename">nss-myhostname.la</code></p></div><div class="refsect1"><a name="idm259768906416"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><span class="command"><strong>nss-myhostname</strong></span> is a plugin for the GNU Name Service Switch
  24                 (NSS) functionality of the GNU C Library (<span class="command"><strong>glibc</strong></span>)
  25                 providing host name resolution for the locally configured system
  26                 hostname as returned by
  27                 <a href="gethostname.html"><span class="citerefentry"><span class="refentrytitle">gethostname</span>(2)</span></a>.
  28                 Various software relies on an always resolvable local host name. When
  29                 using dynamic hostnames this is usually achieved by patching
  30                 <code class="filename">/etc/hosts</code> at the same time as changing the host
  31                 name. This however is not ideal since it requires a writable
  32                 <code class="filename">/etc</code> file system and is fragile because the file
  33                 might be edited by the administrator at the same time. <span class="command"><strong>nss-myhostname</strong></span>
  34                 simply returns all locally configure public IP addresses, or -- if none
  35                 are configured -- the IPv4 address 127.0.0.2 (which is on the local
  36                 loopback) and the IPv6 address ::1 (which is the local host) for
  37                 whatever system hostname is configured locally. Patching
  38                 <code class="filename">/etc/hosts</code> is thus no longer necessary.</p><p>To activate the NSS modules, <code class="option">myhostname</code>
  39                 has to be added to the line starting with "<code class="varname">hosts:</code>" in
  40                 <code class="filename">/etc/nsswitch.conf</code></p><p>It is recommended to put <code class="option">myhostname</code>
  41                 last in the <code class="filename">nsswitch.conf</code> line to make
  42                 sure that this mapping is only used as fallback, and any DNS
  43                 or <code class="filename">/etc/hosts</code> based mapping takes precedence.</p></div><div class="refsect1"><a name="idm259767389856"></a><h2 id="Example">Example<a class="headerlink" title="Permalink to this headline" href="#Example">¶</a></h2><pre class="programlisting">
  44 # /etc/nsswitch.conf
  45
  46 passwd:         compat
  47 group:          compat
  48 shadow:         compat
  49
  50 hosts:          files dns <code class="varname">myhostname</code>
  51 networks:       files
  52
  53 protocols:      db files
  54 services:       db files
  55 ethers:         db files
  56 rpc:            db files
  57
  58 netgroup:       nis
  59                 </pre><p>To test, use <span class="command"><strong>glibc</strong></span>'s <span class="command"><strong>getent</strong></span> tool:</p><pre class="programlisting">
  60 $ getent ahosts `hostname`
  61 ::1             STREAM omega
  62 ::1             DGRAM
  63 ::1             RAW
  64 127.0.0.2       STREAM
  65 127.0.0.2       DGRAM
  66 127.0.0.2       RAW
  67                 </pre><p>In this case the local host name is <code class="varname">omega</code>.</p></div><div class="refsect1"><a name="idm259767384112"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
  68                         <a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
  69                         <a href="systemd-logind.service.html"><span class="citerefentry"><span class="refentrytitle">systemd-logind.service</span>(8)</span></a>,
  70                         <a href="logind.conf.html"><span class="citerefentry"><span class="refentrytitle">logind.conf</span>(5)</span></a>,
  71                         <a href="loginctl.html"><span class="citerefentry"><span class="refentrytitle">loginctl</span>(1)</span></a>,
  72                         <a href="pam.conf.html"><span class="citerefentry"><span class="refentrytitle">pam.conf</span>(5)</span></a>,
  73                         <a href="pam.d.html"><span class="citerefentry"><span class="refentrytitle">pam.d</span>(5)</span></a>,
  74                         <a href="pam.html"><span class="citerefentry"><span class="refentrytitle">pam</span>(8)</span></a>,
  75                         <a href="pam_loginuid.html"><span class="citerefentry"><span class="refentrytitle">pam_loginuid</span>(8)</span></a>
  76                 </p></div></div></body></html>