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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">

<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>