man/systemd-id128.xml

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1+ -->

<refentry id="systemd-id128" xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>systemd-id128</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>systemd-id128</refentrytitle>
    <manvolnum>1</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>systemd-id128</refname>
    <refpurpose>Generate and print sd-128 identifiers</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <cmdsynopsis>
      <command>systemd-id128</command>
      <arg choice="opt" rep="repeat">OPTIONS</arg>
      <arg choice="plain">new</arg>
    </cmdsynopsis>

    <cmdsynopsis>
      <command>systemd-id128</command>
      <arg choice="opt" rep="repeat">OPTIONS</arg>
      <arg choice="plain">machine-id</arg>
    </cmdsynopsis>

    <cmdsynopsis>
      <command>systemd-id128</command>
      <arg choice="opt" rep="repeat">OPTIONS</arg>
      <arg choice="plain">boot-id</arg>
    </cmdsynopsis>

    <cmdsynopsis>
      <command>systemd-id128</command>
      <arg choice="opt" rep="repeat">OPTIONS</arg>
      <arg choice="plain">invocation-id</arg>
    </cmdsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><command>id128</command> may be used to conveniently print
    <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    UUIDs. What identifier is printed depends on the specific verb.</para>

    <para>With <command>new</command>, a new random identifier will be generated.</para>

    <para>With <command>machine-id</command>, the identifier of the current machine will be
    printed. See
    <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
    </para>

    <para>With <command>boot-id</command>, the identifier of the current boot will be
    printed.</para>

    <para>Both <command>machine-id</command> and <command>boot-id</command> may be combined
    with the <option>--app-specific=<replaceable>app-id</replaceable></option> switch to
    generate application-specific IDs. See
    <citerefentry><refentrytitle>sd_id128_get_machine</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    for the discussion when this is useful.</para>

    <para>With <command>invocation-id</command>, the identifier of the current service invocation
    will be printed. This is available in systemd services. See
    <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
    </para>
  </refsect1>

  <refsect1>
    <title>Options</title>

    <para>The following options are understood:</para>

    <variablelist>
      <varlistentry>
        <term><option>-p</option></term>
        <term><option>--pretty</option></term>

        <listitem><para>Generate output as programming language snippets.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-a <replaceable>app-id</replaceable></option></term>
        <term><option>--app-specific=<replaceable>app-id</replaceable></option></term>

        <listitem><para>With this option, an identifier that is the result of hashing the
        application identifier <replaceable>app-id</replaceable> and the machine identifier will be
        printed. The <replaceable>app-id</replaceable> argument must be a valid sd-id128 string
        identifying the application.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-u</option></term>
        <term><option>--uuid</option></term>

        <listitem><para>Generate output as an UUID formatted in the "canonical representation", with five
        groups of digits seperated by hyphens. See the
        <ulink url="https://en.wikipedia.org/wiki/Universally_unique_identifier#Format">wikipedia</ulink>
        for more discussion.</para></listitem>
      </varlistentry>

      <xi:include href="standard-options.xml" xpointer="help" />
      <xi:include href="standard-options.xml" xpointer="version" />
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Exit status</title>

    <para>On success, 0 is returned, a non-zero failure code otherwise.</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>sd_id128_get_machine</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>