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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<refentry id="systemd.image-filter">
<refentryinfo>
<title>systemd.image-filter</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>systemd.image-filter</refentrytitle>
<manvolnum>7</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd.image-filter</refname>
<refpurpose>Disk Image Dissection Filter</refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
<para>In systemd, whenever a disk image (DDI) implementing the <ulink
url="https://uapi-group.org/specifications/specs/discoverable_partitions_specification">UAPI.2 Discoverable
Partitions Specification</ulink> is activated, a filter may be specified controlling which partitions to
consider for mounting. Such a disk image dissection filter is a string that contains per-partition-type
patterns, separated by colons (<literal>:</literal>). The individual rules consist of a partition
identifier, an equal sign (<literal>=</literal>), and a shell globbing pattern applied to the GPT label
string of the partition. See <citerefentry
project='man-pages'><refentrytitle>glob</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
details on shell globbing.</para>
<para>The partition identifiers currently defined are: <option>root</option>, <option>usr</option>,
<option>home</option>, <option>srv</option>, <option>esp</option>, <option>xbootldr</option>,
<option>swap</option>, <option>root-verity</option>, <option>root-verity-sig</option>,
<option>usr-verity</option>, <option>usr-verity-sig</option>, <option>tmp</option>,
<option>var</option>. These identifiers match the relevant partition types in the Discoverable Partitions
Specification, but are agnostic to CPU architectures.</para>
</refsect1>
<refsect1>
<title>Use</title>
<para>Various systemd components that support operating with disk images support a
<option>--image-filter=</option> command line option to specify the image filter to use. If no filter is
specified all partitions in partition table are considered and no per-label filtering is applied (except
that partitions with the <literal>_empty</literal> label are always ignored).</para>
<para>For the host root file system image itself
<citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
is responsible for processing the GPT partition table and making use of the included discoverable
partitions. It accepts an image filter via the kernel command line option
<option>systemd.image_filter=</option>.</para>
</refsect1>
<refsect1>
<title>Examples</title>
<para>The following image filter string dictates that for the root file system partition only partitions
shall be considered whose label begins with <literal>ParticleOS-</literal>. For the
<filename>/usr/</filename> partition the precise label <literal>ParticleOS_47110815</literal> is
required.</para>
<programlisting>root=ParticleOS-*:usr=ParticleOS_47110815</programlisting>
</refsect1>
<refsect1>
<title>See Also</title>
<para><simplelist type="inline">
<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>systemd-dissect</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>systemd.image-policy</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
</simplelist></para>
</refsect1>
</refentry>
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