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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_randomize">
+
+        <refentryinfo>
+                <title>sd_id128_randomize</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_randomize</refentrytitle>
+                <manvolnum>3</manvolnum>
+        </refmeta>
+
+        <refnamediv>
+                <refname>sd_id128_randomize</refname>
+                <refname>sd_id128_get_machine</refname>
+                <refname>sd_id128_get_boot</refname>
+                <refpurpose>Generate or retrieve 128 bit IDs</refpurpose>
+        </refnamediv>
+
+        <refsynopsisdiv>
+                <funcsynopsis>
+                        <funcsynopsisinfo>#include &lt;systemd/sd-id128.h&gt;</funcsynopsisinfo>
+
+                        <funcprototype>
+                                <funcdef>int <function>sd_id128_randomize</function></funcdef>
+                                <paramdef>sd_id128_t* <parameter>ret</parameter></paramdef>
+                        </funcprototype>
+
+                        <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_randomize()</function>
+                generates a new randomized 128 bit ID and returns it
+                in <parameter>ret</parameter>. Every invocation
+                returns a new randomly generated ID. This uses the
+                <filename>/dev/urandom</filename> kernel random number
+                generator.</para>
+
+                <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><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_randomize()</function> and
+                <function>sd_id128_get_boot()</function> always return
+                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 an 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>7</manvolnum></citerefentry>.</para>
+
+                <para><citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
+                <literal>--new-id</literal> command may be used as
+                command line front-end for
+                <function>sd_id128_randomize()</function>.</para>
+        </refsect1>
+
+        <refsect1>
+                <title>Return Value</title>
+
+                <para>The three calls returns 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_randomize()</function>,
+                <function>sd_id128_get_machine()</function> and
+                <function>sd_id128_get_boot()</function> interfaces
+                are available as shared library, which can be compiled
+                and linked to with the
+                <literal>libsystemd-id128</literal>
+                <citerefentry><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>7</manvolnum></citerefentry>,
+                        <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+                        <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry>
+                </para>
+        </refsect1>
+
+</refentry>