mirror of
https://github.com/morgan9e/systemd
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85afe4760b
Let's automatically generate validatefs xattrs by default, that encode the intended use of partitions. This defaults to on, since the structure of repart definition files tells us enough on use for this to be safe. There's an option however, to turn this off.
112 lines
5.5 KiB
XML
112 lines
5.5 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="systemd-validatefs_.service" conditional='HAVE_BLKID'
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>systemd-validatefs@.service</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd-validatefs@.service</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-validatefs@.service</refname>
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<refpurpose>Validate File System Mount Constraint Data</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>systemd-validatefs@.service</filename></para>
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<para><filename>/usr/lib/systemd/systemd-validatefs</filename> <optional><replaceable>DEVICE</replaceable></optional></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><filename>systemd-validatefs@.service</filename> is a system service template that can be
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instantiated for newly established mount points. It reads file system mount constraint data from the file
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system, and ensures the mount runtime setup matches it. If it doesn't the service fails, which effects an
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immediate reboot.</para>
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<para>This functionality is supposed to ensure that trusted file systems cannot be used in a different
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context then what they were intended for. More specifically: in an
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<citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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based environment the file systems to mount are largely auto-discovered based on (unprotected) GPT
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partition table data. The mount constraint information can be used to validate the GPT partition data,
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based on the (protected) file system contents.</para>
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<para>Specifically, the mount constraints are encoded in the following extended attributes on the root
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inode of the file systems:</para>
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<orderedlist>
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<listitem><para><varname>user.validatefs.mount_point</varname>: this extended attribute shall contain
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one or more absolute, normalized paths, separated by NUL bytes. If set and the specified file system is
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mounted to a location not matching any of the listed paths the validation check will
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fail.</para></listitem>
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<listitem><para><varname>user.validatefs.gpt_label</varname>: this extended attribute may contain a
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free-form string. It is compared with the partition label string of the partition this file system is
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located on, and if different the validation will fail.</para></listitem>
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<listitem><para><varname>user.validatefs.gpt_type_uuid</varname>: this extended attribute may contain a
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GPT partition type UUID formatted as string. It is compared with the partition type UUID of the
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partition this file system is located on, and if different the validation will fail.</para></listitem>
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</orderedlist>
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<para>The <filename>systemd-validatefs@.service</filename> unit is automatically pulled into the initial
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transaction by
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<citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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for all file systems it discovers and generates mounts
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for. <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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will do this for all mounts with the <option>x-systemd.validatefs</option> mount option in
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<filename>/etc/fstab</filename>.</para>
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<para>The
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<citerefentry><refentrytitle>systemd-repart</refentrytitle><manvolnum>8</manvolnum></citerefentry> tool
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generates these extended attributes automatically for the file systems it puts together, which may be
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controlled with the <varname>AddValidateFS=</varname> configuration option.</para>
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</refsect1>
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<refsect1>
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<title>Options</title>
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<para>The <filename>/usr/lib/systemd/system-validatefs</filename> executable may also be invoked from the
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command line, where it expects a path to a mount and the following options:</para>
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<variablelist>
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<varlistentry>
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<term><option>--root=</option></term>
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<listitem><para>Takes an absolute path or the special string <literal>auto</literal>. The specified
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path if removed as prefix from the specified mount point argument before the validation. If set to
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<literal>auto</literal> defaults to unspecified on the host and <filename>/sysroot/</filename> when
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run in initrd context, in order to validate the mount constraint data relative to the future file
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system root.</para>
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<xi:include href="version-info.xml" xpointer="v258"/></listitem>
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</varlistentry>
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<xi:include href="standard-options.xml" xpointer="help" />
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<xi:include href="standard-options.xml" xpointer="version" />
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</variablelist>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para><simplelist type="inline">
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<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>systemd-repart</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
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</simplelist></para>
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</refsect1>
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</refentry>
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