134 lines
5.8 KiB
XML
134 lines
5.8 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2011 Lennart Poettering
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Copyright 2013 Tom Gundersen
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="nss-myhostname" conditional='HAVE_MYHOSTNAME'>
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<refentryinfo>
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<title>nss-myhostname</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>nss-myhostname</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>nss-myhostname</refname>
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<refpurpose>Provide hostname resolution for the locally
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configured system hostname.</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>nss-myhostname.la</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><command>nss-myhostname</command> is a plugin for the GNU Name Service Switch
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(NSS) functionality of the GNU C Library (<command>glibc</command>)
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providing hostname resolution for the locally configured system
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hostname as returned by
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<citerefentry><refentrytitle>gethostname</refentrytitle><manvolnum>2</manvolnum></citerefentry>.
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Various software relies on an always-resolvable local hostname. When
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using dynamic hostnames, this is usually achieved by patching
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<filename>/etc/hosts</filename> at the same time as changing the host
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name. This however is not ideal since it requires a writable
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<filename>/etc</filename> file system and is fragile because the file
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might be edited by the administrator at the same time. <command>nss-myhostname</command>
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simply returns all locally configured public IP addresses, or, if none
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are configured, the IPv4 address 127.0.0.2 (which is on the local
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loopback) and the IPv6 address ::1 (which is the local host) for
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whatever system hostname is configured locally. Patching
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<filename>/etc/hosts</filename> is thus no longer necessary.</para>
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<para>To activate the NSS modules, <option>myhostname</option>
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has to be added to the line starting with "<varname>hosts:</varname>" in
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<filename>/etc/nsswitch.conf</filename></para>
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<para>It is recommended to put <option>myhostname</option>
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last in the <filename>nsswitch.conf</filename> line to make
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sure that this mapping is only used as fallback, and any DNS
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or <filename>/etc/hosts</filename> based mapping takes precedence.</para>
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</refsect1>
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<refsect1>
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<title>Example</title>
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<programlisting># /etc/nsswitch.conf
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passwd: compat
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group: compat
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shadow: compat
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hosts: files dns <varname>myhostname</varname>
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networks: files
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protocols: db files
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services: db files
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ethers: db files
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rpc: db files
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netgroup: nis</programlisting>
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<para>To test, use <command>glibc</command>'s <command>getent</command> tool:</para>
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<programlisting>$ getent ahosts `hostname`
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::1 STREAM omega
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::1 DGRAM
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::1 RAW
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127.0.0.2 STREAM
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127.0.0.2 DGRAM
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127.0.0.2 RAW</programlisting>
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<para>In this case the local hostname is <varname>omega</varname>.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>logind.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>loginctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>pam.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>pam.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry project='die-net'><refentrytitle>pam_loginuid</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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