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This documents two possible values expected by the option root-hash-signature for veritytab and veritysetup-generator.
199 lines
9.2 KiB
XML
199 lines
9.2 KiB
XML
<?xml version="1.0"?>
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<!--*-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/4.2/docbookx.dtd">
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<!--
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SPDX-License-Identifier: LGPL-2.1-or-later
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This is based on crypttab(5).
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-->
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<refentry id="veritytab" conditional='HAVE_LIBCRYPTSETUP' xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>veritytab</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>veritytab</refentrytitle>
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<manvolnum>5</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>veritytab</refname>
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<refpurpose>Configuration for verity block devices</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>/etc/veritytab</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>The <filename>/etc/veritytab</filename> file describes
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verity protected block devices that are set up during
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system boot.</para>
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<para>Empty lines and lines starting with the <literal>#</literal>
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character are ignored. Each of the remaining lines describes one
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verity protected block device. Fields are delimited by
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white space.</para>
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<para>Each line is in the form<programlisting><replaceable>volume-name</replaceable> <replaceable>data-device</replaceable> <replaceable>hash-device</replaceable> <replaceable>roothash</replaceable> <replaceable>options</replaceable></programlisting>
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The first four fields are mandatory, the remaining one is optional.</para>
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<para>The first field contains the name of the resulting verity volume; its block device is set up
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below <filename>/dev/mapper/</filename>.</para>
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<para>The second field contains a path to the underlying block data device, or a specification of a block device via
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<literal>UUID=</literal> followed by the UUID.</para>
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<para>The third field contains a path to the underlying block hash device, or a specification of a block device via
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<literal>UUID=</literal> followed by the UUID.</para>
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<para>The fourth field is the <literal>roothash</literal> in hexadecimal.</para>
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<para>The fifth field, if present, is a comma-delimited list of options. The following options are
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recognized:</para>
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<variablelist class='fstab-options'>
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<varlistentry>
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<term><option>ignore-corruption</option></term>
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<term><option>restart-on-corruption</option></term>
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<term><option>panic-on-corruption</option></term>
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<listitem><para>Defines what to do if a data verity problem is detected (data corruption). Without these
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options kernel fails the IO operation with I/O error. With <literal>--ignore-corruption</literal> option the
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corruption is only logged. With <literal>--restart-on-corruption</literal> or
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<literal>--panic-on-corruption</literal> the kernel is restarted (panicked) immediately.
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(You have to provide way how to avoid restart loops.)</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>ignore-zero-blocks</option></term>
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<listitem><para>Instruct kernel to not verify blocks that are expected to contain zeroes and always directly
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return zeroes instead.
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WARNING: Use this option only in very specific cases. This option is available since Linux kernel version 4.5.
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</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>check-at-most-once</option></term>
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<listitem><para>Instruct kernel to verify blocks only the first time they are read from the data device, rather
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than every time.
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WARNING: It provides a reduced level of security because only offline tampering of the data device's content
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will be detected, not online tampering. This option is available since Linux kernel version 4.17.
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</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>root-hash-signature=<replaceable>PATH</replaceable>|base64:<replaceable>HEX</replaceable></option></term>
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<listitem><para>A base64 string encoding the root hash signature prefixed by <literal>base64:</literal> or a
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path to roothash signature file used to verify the root hash (in kernel). This feature requires Linux kernel
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version 5.4 or more recent.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>_netdev</option></term>
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<listitem><para>Marks this veritysetup device as requiring network. It will be
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started after the network is available, similarly to
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<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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units marked with <option>_netdev</option>. The service unit to set up this device
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will be ordered between <filename>remote-fs-pre.target</filename> and
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<filename>remote-veritysetup.target</filename>, instead of
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<filename>veritysetup-pre.target</filename> and
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<filename>veritysetup.target</filename>.</para>
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<para>Hint: if this device is used for a mount point that is specified in
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<citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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the <option>_netdev</option> option should also be used for the mount
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point. Otherwise, a dependency loop might be created where the mount point
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will be pulled in by <filename>local-fs.target</filename>, while the
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service to configure the network is usually only started <emphasis>after</emphasis>
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the local file system has been mounted.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>noauto</option></term>
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<listitem><para>This device will not be added to <filename>veritysetup.target</filename>.
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This means that it will not be automatically enabled on boot, unless something else pulls
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it in. In particular, if the device is used for a mount point, it'll be enabled
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automatically during boot, unless the mount point itself is also disabled with
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<option>noauto</option>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>nofail</option></term>
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<listitem><para>This device will not be a hard dependency of
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<filename>veritysetup.target</filename>. It'll still be pulled in and started, but the system
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will not wait for the device to show up and be enabled, and boot will not fail if this is
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unsuccessful. Note that other units that depend on the enabled device may still fail. In
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particular, if the device is used for a mount point, the mount point itself also needs to
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have the <option>nofail</option> option, or the boot will fail if the device is not enabled
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successfully.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>x-initrd.attach</option></term>
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<listitem><para>Setup this verity protected block device in the initramfs, similarly to
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<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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units marked with <option>x-initrd.mount</option>.</para>
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<para>Although it's not necessary to mark the mount entry for the root file system with
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<option>x-initrd.mount</option>, <option>x-initrd.attach</option> is still recommended with
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the verity protected block device containing the root file system as otherwise systemd
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will attempt to detach the device during the regular system shutdown while it's still in
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use. With this option the device will still be detached but later after the root file
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system is unmounted.</para>
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<para>All other verity protected block devices that contain file systems mounted in the
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initramfs should use this option.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>At early boot and when the system manager configuration is
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reloaded, this file is translated into native systemd units by
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<citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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<example>
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<title>/etc/veritytab example</title>
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<para>Set up two verity protected block devices. One using device blocks, another using files.</para>
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<programlisting>usr PARTUUID=783e45ae-7aa3-484a-beef-a80ff9c19cbb PARTUUID=21dc1dfe-4c33-8b48-98a9-918a22eb3e37 36e3f740ad502e2c25e2a23d9c7c17bf0fdad2300b7580842d4b7ec1fb0fa263 auto
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data /etc/data /etc/hash a5ee4b42f70ae1f46a08a7c92c2e0a20672ad2f514792730f5d49d7606ab8fdf auto
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</programlisting>
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</example>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-veritysetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry project='die-net'><refentrytitle>veritysetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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</para>
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</refsect1>
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</refentry>
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