systemd/man/systemd-id128.xml
Zbigniew Jędrzejewski-Szmek b37e8184a5 id128: allow combining --app with show
This effectively exposes sd_id128_get_app_specific() on the commandline.

Fixes https://github.com/systemd/systemd/issues/27514.
2023-09-02 14:17:29 +03:00

207 lines
7.5 KiB
XML

<?xml version='1.0'?> <!--*-nxml-*-->
<!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-or-later -->
<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>
<cmdsynopsis>
<command>systemd-id128</command>
<arg choice="opt" rep="repeat">OPTIONS</arg>
<arg choice="plain">show</arg>
<arg choice="opt" rep="repeat">NAME|UUID</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>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>
<para>With <command>show</command>, well-known IDs are printed (for now, only GPT partition type UUIDs),
along with brief identifier strings. When no arguments are specified, all known IDs are shown. When
arguments are specified, they may be the identifiers or ID values of one or more known IDs, which are
then printed with their name, or arbitrary IDs, which are then printed with a placeholder name. Combine
with <option>--uuid</option> to list the IDs in UUID style, i.e. the way GPT partition type UUIDs are
usually shown.</para>
<para><command>machine-id</command>, <command>boot-id</command>, and <command>show</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>
</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>
<xi:include href="version-info.xml" xpointer="v240"/></listitem>
</varlistentry>
<varlistentry>
<term><option>-P</option></term>
<term><option>--value</option></term>
<listitem><para>Only print the value. May be combined with
<option>-u</option>/<option>--uuid</option>.</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, identifiers will be printed that are the result of hashing the
application identifier <replaceable>app-id</replaceable> and another ID. The
<replaceable>app-id</replaceable> argument must be a valid sd-id128 string identifying the
application. When used with <command>machine-id</command>, the other ID will be the machine ID as
described in
<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>, when
used with <command>boot-id</command>, the other ID will be the boot ID, and when used with
<command>show</command>, the other ID or IDs should be specified via the positional arguments.</para>
<xi:include href="version-info.xml" xpointer="v240"/>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-u</option></term>
<term><option>--uuid</option></term>
<listitem><para>Generate output as a UUID formatted in the "canonical representation", with five
groups of digits separated by hyphens. See the
<ulink url="https://en.wikipedia.org/wiki/Universally_unique_identifier#Format">wikipedia</ulink>
for more discussion.</para>
<xi:include href="version-info.xml" xpointer="v244"/></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, and a non-zero failure code otherwise.</para>
</refsect1>
<refsect1>
<title>Examples</title>
<example>
<title>Show a well-known UUID</title>
<programlisting>
$ systemd-id128 show -P user-home
773f91ef66d449b5bd83d683bf40ad16
$ systemd-id128 show -Pu user-home
773f91ef-66d4-49b5-bd83-d683bf40ad16
$ systemd-id128 show 773f91ef-66d4-49b5-bd83-d683bf40ad16
NAME ID
user-home 773f91ef66d449b5bd83d683bf40ad16
</programlisting>
</example>
<example>
<title>Generate an application-specific UUID</title>
<programlisting>
$ systemd-id128 machine-id -u
3a9d668b-4db7-4939-8a4a-5e78a03bffb7
$ systemd-id128 new -u
1fb8f24b-02df-458d-9659-cc8ace68e28a
$ systemd-id128 --app=1fb8f24b-02df-458d-9659-cc8ace68e28a
47b82cb1-5339-43da-b2a6-1c350aef1bd1
$ systemd-id128 -Pu show 3a9d668b-4db7-4939-8a4a-5e78a03bffb7 --app=1fb8f24b-02df-458d-9659-cc8ace68e28a
47b82cb1-5339-43da-b2a6-1c350aef1bd1
</programlisting>
<para>On a given machine with the ID 3a9d668b-4db7-4939-8a4a-5e78a03bffb7, for the application
1fb8f24b-02df-458d-9659-cc8ace68e28a, we generate an application-specific machine ID. If we want to
later recreate the same calculation on a different machine, we need to specify both IDs explicitly.
</para>
</example>
</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>