1 <?xml version='1.0'?> <!--*-nxml-*-->
2 <?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?>
3 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
4 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
7 This file is part of systemd.
9 Copyright 2010 Lennart Poettering
11 systemd is free software; you can redistribute it and/or modify it
12 under the terms of the GNU General Public License as published by
13 the Free Software Foundation; either version 2 of the License, or
14 (at your option) any later version.
16 systemd is distributed in the hope that it will be useful, but
17 WITHOUT ANY WARRANTY; without even the implied warranty of
18 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19 General Public License for more details.
21 You should have received a copy of the GNU General Public License
22 along with systemd; If not, see <http://www.gnu.org/licenses/>.
25 <refentry id="machine-id">
27 <title>/etc/machine-id</title>
28 <productname>systemd</productname>
32 <contrib>Developer</contrib>
33 <firstname>Lennart</firstname>
34 <surname>Poettering</surname>
35 <email>lennart@poettering.net</email>
41 <refentrytitle>machine-id</refentrytitle>
42 <manvolnum>5</manvolnum>
46 <refname>machine-id</refname>
47 <refpurpose>local machine ID configuration file</refpurpose>
51 <para><filename>/etc/machine-id</filename></para>
55 <title>Description</title>
57 <para>The <filename>/etc/machine-id</filename> file
58 configures the unique machine id of the local system
59 that is set during installation. It should contain a
60 single newline-terminated, hexadecimal, lowercase 16
61 character machine ID string.</para>
63 <para>The machine ID is usually generated from a
64 random source during system installation and stays
65 constant for all subsequent boots. Optionally, for
66 stateless systems it is generated during runtime at
67 boot if it is found to be empty.</para>
69 <para>The machine ID does not change based on user
70 configuration, or when hardware is replaced.</para>
72 <para>This machine id follows the same format and
73 logic as the D-Bus machine ID.</para>
75 <para>Programs may use this ID to identify the host
76 with a globally unique ID in the network, that does
77 not change even if the local network configuration
78 changes. Due to this and its greater length it is
79 a more useful replacement for the
80 <citerefentry><refentrytitle>gethostid</refentrytitle><manvolnum>3</manvolnum></citerefentry>
81 call POSIX specifies.</para>
85 <title>History</title>
87 <para>The simple configuration file format of
88 <filename>/etc/machine-id</filename> originates in the
89 <filename>/var/lib/dbus/machine-id</filename> file
90 introduced by D-Bus. In fact this latter file might be a
92 <varname>/etc/machine-id</varname>.</para>
96 <title>See Also</title>
98 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
99 <citerefentry><refentrytitle>gethostid</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
100 <citerefentry><refentrytitle>hostname</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
101 <citerefentry><refentrytitle>machine-info</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
102 <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>