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authorLennart Poettering <lennart@poettering.net>2011-03-04 21:53:19 +0100
committerLennart Poettering <lennart@poettering.net>2011-03-04 21:53:19 +0100
commitd7ccca2e3f86feb81a48e243d8bad78814659a74 (patch)
tree93f0063f961ec21b31546778add98c3b1cfe5c21 /man/machine-id.xml
parent63a723f3a7caf4eb1bc46a3849f59f27337924b7 (diff)
main: introduce /etc/machine-id
This is supposed to play the same roles /var/lib/dbus/machine-id, however fixes a couple of problems: - It is available during early boot since it is stored in /etc - Removes the ID from the D-Bus context and moves it into a system context, thus hopefully lowering hesitation by people to use it. - It is generated at installation time. If the file is empty at boot time it will be mounted over with a randomly generated ID, which is not saved to disk. This is useful to support state-less machines with no transient or writable /etc configuration.
Diffstat (limited to 'man/machine-id.xml')
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diff --git a/man/machine-id.xml b/man/machine-id.xml
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+<?xml version='1.0'?> <!--*-nxml-*-->
+<?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<!--
+ This file is part of systemd.
+
+ Copyright 2010 Lennart Poettering
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<refentry id="machine-id">
+ <refentryinfo>
+ <title>/etc/machine-id</title>
+ <productname>systemd</productname>
+
+ <authorgroup>
+ <author>
+ <contrib>Developer</contrib>
+ <firstname>Lennart</firstname>
+ <surname>Poettering</surname>
+ <email>lennart@poettering.net</email>
+ </author>
+ </authorgroup>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>machine-id</refentrytitle>
+ <manvolnum>5</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>machine-id</refname>
+ <refpurpose>local machine ID configuration file</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <para><filename>/etc/machine-id</filename></para>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para>The <filename>/etc/machine-id</filename> file
+ configures the unique machine id of the local system
+ that is set during installation. It should contain a
+ single newline-terminated, hexadecimal, lowercase 16
+ character machine ID string.</para>
+
+ <para>The machine ID is usually generated from a
+ random source during system installation and stays
+ constant for all subsequent boots. Optionally, for
+ stateless systems it is generated during runtime at
+ boot.</para>
+
+ <para>The machine ID does not change based on user
+ configuration, or when hardware is replaced.</para>
+
+ <para>This machine id follows the same format and
+ logic as the D-Bus machine ID.</para>
+
+ <para>Programs may use this ID to identify the host
+ with a globally unique ID in the network, that does
+ not change even if the local network configuration
+ changes. Due to this and its greater length it is
+ a more useful replacement than the
+ <citerefentry><refentrytitle>gethostid</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ call POSIX specifies.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>History</title>
+
+ <para>The simple configuration file format of
+ <filename>/etc/machine-id</filename> originates in the
+ <filename>/var/lib/dbus/machine-id</filename> file
+ introduced by D-Bus. In fact this latter file might be a
+ symlink to the
+ <varname>/etc/machine-id</varname>.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+ <para>
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>gethostid</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>hostname</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>