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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/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<refentry id="systemd-mountfsd.service" conditional='ENABLE_MOUNTFSD'>
<refentryinfo>
<title>systemd-mountfsd.service</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>systemd-mountfsd.service</refentrytitle>
<manvolnum>8</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd-mountfsd.service</refname>
<refname>systemd-mountfsd</refname>
<refpurpose>Disk Image File System Mount Service</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename>systemd-mountfsd.service</filename></para>
<para><filename>/usr/lib/systemd/systemd-mountfsd</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><command>systemd-mountfsd</command> is a system service that dissects disk images, and returns mount
file descriptors for the file systems contained therein to clients, via a Varlink IPC API.</para>
<para>The disk images provided must contain a raw file system image or must follow the <ulink
url="https://uapi-group.org/specifications/specs/discoverable_partitions_specification/">Discoverable
Partitions Specification</ulink>. Before mounting any file systems authenticity of the disk image is
established in one or a combination of the following ways:</para>
<orderedlist>
<listitem><para>If the disk image is located in a regular file in one of the directories
<filename>/var/lib/machines/</filename>, <filename>/var/lib/portables/</filename>,
<filename>/var/lib/extensions/</filename>, <filename>/var/lib/confexts/</filename> or their
counterparts in the <filename>/etc/</filename>, <filename>/run/</filename>,
<filename>/usr/lib/</filename> it is assumed to be trusted.</para></listitem>
<listitem><para>If the disk image contains a Verity enabled disk image, along with a signature
partition with a key in the kernel keyring or in <filename>/etc/verity.d/</filename> (and related
directories) the disk image is considered trusted.</para></listitem>
</orderedlist>
<para>This service provides one <ulink url="https://varlink.org/">Varlink</ulink> service:
<constant>io.systemd.MountFileSystem</constant> which accepts a file descriptor to a regular file or
block device, and returns a number of file descriptors referring to an <function>fsmount()</function>
file descriptor the client may then attach to a path of their choice.</para>
<para>The returned mounts are automatically allowlisted in the per-user-namespace allowlist maintained by
<citerefentry><refentrytitle>systemd-nsresourced.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
<para>The file systems are automatically fsck'ed before mounting.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-nsresourced.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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