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101 lines
4.0 KiB
XML
101 lines
4.0 KiB
XML
<?xml version="1.0"?>
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<!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "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 2014 Didier Roche
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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="systemd-machine-id-commit.service">
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<refentryinfo>
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<title>systemd-machine-id-commit.service</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>Didier</firstname>
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<surname>Roche</surname>
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<email>didrocks@ubuntu.com</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>systemd-machine-id-commit.service</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-machine-id-commit.service</refname>
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<refpurpose>Commit transient machine-id to disk</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>systemd-machine-id-commit.service</filename></para>
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<para><filename>/usr/lib/systemd/systemd-machine-id-commit</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><filename>systemd-machine-id-commit.service</filename> is a
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service responsible for committing any transient
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<filename>/etc/machine-id</filename> file to a writable file
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system. See
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<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for more information about this file.</para>
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<para>This service is started shortly after
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<filename>local-fs.target</filename> if
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<filename>/etc/machine-id</filename> is an independent mount point
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(probably a tmpfs one) and /etc is writable.
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<command>systemd-machine-id-commit</command> will then write
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current machine ID to disk and unmount the transient
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<filename>/etc/machine-id</filename> file in a race-free manner to
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ensure that file is always valid for other processes.</para>
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<para>Note that the traditional way to initialize the machine ID
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in <filename>/etc/machine-id</filename> is to use
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<command>systemd-machine-id-setup</command> by system installer
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tools. You can also use
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<citerefentry><refentrytitle>systemd-firstboot</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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to initialize the machine ID on mounted (but not booted) system
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images. The main use case for that service is
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<filename>/etc/machine-id</filename> being an empty file at boot
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and initrd chaining to systemd giving it a read only file system
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that will be turned read-write later during the boot
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process.</para>
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<para>There is no consequence if that service fails other than a
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newer machine-id will be generated during next system boot.
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</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-machine-id-commit</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-machine-id-setup</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-firstboot</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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