12b42c7667
This did not really work out as we had hoped. Trying to do this upstream introduced several problems that probably makes it better suited as a downstream patch after all. At any rate, it is not releaseable in the current state, so we at least need to revert this before the release. * by adjusting the path to binaries, but not do the same thing to the search path we end up with inconsistent man-pages. Adjusting the search path too would be quite messy, and it is not at all obvious that this is worth the effort, but at any rate it would have to be done before we could ship this. * this means that distributed man-pages does not make sense as they depend on config options, and for better or worse we are still distributing man pages, so that is something that definitely needs sorting out before we could ship with this patch. * we have long held that split-usr is only minimally supported in order to boot, and something we hope will eventually go away. So before we start adding even more magic/effort in order to make this work nicely, we should probably question if it makes sense at all.
141 lines
5.6 KiB
XML
141 lines
5.6 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 2010 Lennart Poettering
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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="machine-id">
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<refentryinfo>
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<title>machine-id</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>machine-id</refentrytitle>
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<manvolnum>5</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>machine-id</refname>
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<refpurpose>Local machine ID configuration file</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>/etc/machine-id</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>The <filename>/etc/machine-id</filename> file contains the
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unique machine ID of the local system that is set during
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installation. The machine ID is a single newline-terminated,
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hexadecimal, 32-character, lowercase machine ID string. When
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decoded from hexadecimal, this corresponds with a 16-byte/128-bit
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string.</para>
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<para>The machine ID is usually generated from a random source
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during system installation and stays constant for all subsequent
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boots. Optionally, for stateless systems, it is generated during
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runtime at boot if it is found to be empty.</para>
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<para>The machine ID does not change based on user configuration
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or when hardware is replaced.</para>
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<para>This machine ID adheres to the same format and logic as the
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D-Bus machine ID.</para>
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<para>Programs may use this ID to identify the host with a
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globally unique ID in the network, which does not change even if
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the local network configuration changes. Due to this and its
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greater length, it is a more useful replacement for the
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<citerefentry project='man-pages'><refentrytitle>gethostid</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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call that POSIX specifies.</para>
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<para>The
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<citerefentry><refentrytitle>systemd-machine-id-setup</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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tool may be used by installer tools to initialize the machine ID
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at install time. Use
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<citerefentry><refentrytitle>systemd-firstboot</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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to initialize it on mounted (but not booted) system images.</para>
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</refsect1>
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<refsect1>
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<title>Relation to OSF UUIDs</title>
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<para>Note that the machine ID historically is not an OSF UUID as
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defined by <ulink url="https://tools.ietf.org/html/rfc4122">RFC
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4122</ulink>, nor a Microsoft GUID; however, starting with systemd
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v30, newly generated machine IDs do qualify as v4 UUIDs.</para>
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<para>In order to maintain compatibility with existing
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installations, an application requiring a UUID should decode the
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machine ID, and then apply the following operations to turn it
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into a valid OSF v4 UUID. With <literal>id</literal> being an
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unsigned character array:</para>
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<programlisting>/* Set UUID version to 4 --- truly random generation */
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id[6] = (id[6] & 0x0F) | 0x40;
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/* Set the UUID variant to DCE */
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id[8] = (id[8] & 0x3F) | 0x80;</programlisting>
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<para>(This code is inspired by
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<literal>generate_random_uuid()</literal> of
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<filename>drivers/char/random.c</filename> from the Linux kernel
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sources.)</para>
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</refsect1>
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<refsect1>
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<title>History</title>
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<para>The simple configuration file format of
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<filename>/etc/machine-id</filename> originates in the
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<filename>/var/lib/dbus/machine-id</filename> file introduced by
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D-Bus. In fact, this latter file might be a symlink to
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<varname>/etc/machine-id</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-machine-id-setup</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>gethostid</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>hostname</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>machine-info</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_id128_get_machine</refentrytitle><manvolnum>3</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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