138 lines
6.0 KiB
XML
138 lines
6.0 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 2012 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="sd_id128_get_machine">
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<refentryinfo>
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<title>sd_id128_get_machine</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>sd_id128_get_machine</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_id128_get_machine</refname>
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<refname>sd_id128_get_boot</refname>
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<refpurpose>Retrieve 128-bit IDs</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-id128.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_id128_get_machine</function></funcdef>
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<paramdef>sd_id128_t* <parameter>ret</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_id128_get_boot</function></funcdef>
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<paramdef>sd_id128_t* <parameter>ret</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_id128_get_machine()</function>
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returns the machine ID of the executing host. This
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reads and parses the
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<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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file. This function caches the machine ID internally
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to make retrieving the machine ID a cheap
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operation.</para>
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<para><function>sd_id128_get_boot()</function> returns
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the boot ID of the executing kernel. This reads and
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parses the
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<filename>/proc/sys/kernel/random/boot_id</filename>
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file exposed by the kernel. It is randomly generated
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early at boot and is unique for every running kernel
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instance. See
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<citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry>
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for more information. This function also internally
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caches the returned ID to make this call a cheap
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operation.</para>
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<para>Note that
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<function>sd_id128_get_boot()</function> always returns
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a UUID v4 compatible
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ID. <function>sd_id128_get_machine()</function> will
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also return a UUID v4-compatible ID on new
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installations but might not on older. It is possible
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to convert the machine ID into a UUID v4-compatible
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one. For more information, see
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<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
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<para>For more information about the
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<literal>sd_id128_t</literal> type see
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<citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>The two calls return 0 on success (in which
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case <parameter>ret</parameter> is filled in), or a
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negative errno-style error code.</para>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para>The <function>sd_id128_get_machine()</function>
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and <function>sd_id128_get_boot()</function>
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interfaces are available as a shared library, which can
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be compiled and linked to with the
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<literal>libsystemd</literal> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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file.</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>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_id128_randomize</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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