systemd/man/sd_id128_get_machine.xml
Tom Gundersen 12b42c7667 man: revert dynamic paths for split-usr setups
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.
2015-06-18 19:47:44 +02:00

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<?xml version='1.0'?> <!--*-nxml-*-->
<!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 2012 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refentry id="sd_id128_get_machine">
<refentryinfo>
<title>sd_id128_get_machine</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>sd_id128_get_machine</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_id128_get_machine</refname>
<refname>sd_id128_get_boot</refname>
<refpurpose>Retrieve 128-bit IDs</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include &lt;systemd/sd-id128.h&gt;</funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_id128_get_machine</function></funcdef>
<paramdef>sd_id128_t *<parameter>ret</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_id128_get_boot</function></funcdef>
<paramdef>sd_id128_t *<parameter>ret</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_id128_get_machine()</function> returns the
machine ID of the executing host. This reads and parses the
<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>
file. This function caches the machine ID internally to make
retrieving the machine ID a cheap operation.</para>
<para><function>sd_id128_get_boot()</function> returns the boot ID
of the executing kernel. This reads and parses the
<filename>/proc/sys/kernel/random/boot_id</filename> file exposed
by the kernel. It is randomly generated early at boot and is
unique for every running kernel instance. See
<citerefentry project='man-pages'><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry>
for more information. This function also internally caches the
returned ID to make this call a cheap operation.</para>
<para>Note that <function>sd_id128_get_boot()</function> always
returns a UUID v4 compatible ID.
<function>sd_id128_get_machine()</function> will also return a
UUID v4-compatible ID on new installations but might not on older.
It is possible to convert the machine ID into a UUID v4-compatible
one. For more information, see
<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
<para>For more information about the <literal>sd_id128_t</literal>
type see
<citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>The two calls return 0 on success (in which case
<parameter>ret</parameter> is filled in), or a negative
errno-style error code.</para>
</refsect1>
<refsect1>
<title>Notes</title>
<para>The <function>sd_id128_get_machine()</function> and
<function>sd_id128_get_boot()</function> interfaces are available
as a shared library, which can be compiled and linked to with the
<literal>libsystemd</literal> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
file.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_id128_randomize</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>