man/veritytab.xml - systemd - Git at Google

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 <!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

 This is based on crypttab(5).

 -->
 <refentry id="veritytab" conditional='HAVE_LIBCRYPTSETUP' xmlns:xi="http://www.w3.org/2001/XInclude">

   <refentryinfo>
     <title>veritytab</title>
     <productname>systemd</productname>
   </refentryinfo>

   <refmeta>
     <refentrytitle>veritytab</refentrytitle>
     <manvolnum>5</manvolnum>
   </refmeta>

   <refnamediv>
     <refname>veritytab</refname>
     <refpurpose>Configuration for verity block devices</refpurpose>
   </refnamediv>

   <refsynopsisdiv>
     <para><filename>/etc/veritytab</filename></para>
   </refsynopsisdiv>

   <refsect1>
     <title>Description</title>

     <para>The <filename>/etc/veritytab</filename> file describes
     verity protected block devices that are set up during
     system boot.</para>

     <para>Empty lines and lines starting with the <literal>#</literal>
     character are ignored. Each of the remaining lines describes one
     verity protected block device. Fields are delimited by
     white space.</para>

     <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>
     The first four fields are mandatory, the remaining one is optional.</para>

     <para>The first field contains the name of the resulting verity volume; its block device is set up
     below <filename>/dev/mapper/</filename>.</para>

     <para>The second field contains a path to the underlying block data device, or a specification of a block device via
     <literal>UUID=</literal> followed by the UUID.</para>

     <para>The third field contains a path to the underlying block hash device, or a specification of a block device via
     <literal>UUID=</literal> followed by the UUID.</para>

     <para>The fourth field is the <literal>roothash</literal> in hexadecimal.</para>

     <para>The fifth field, if present, is a comma-delimited list of options. The following options are
     recognized:</para>

     <variablelist class='fstab-options'>

       <varlistentry>
         <term><option>ignore-corruption</option></term>
         <term><option>restart-on-corruption</option></term>
         <term><option>panic-on-corruption</option></term>

         <listitem><para>Defines what to do if a data verity problem is detected (data corruption). Without these
         options kernel fails the IO operation with I/O error. With <literal>--ignore-corruption</literal> option the
         corruption is only logged. With <literal>--restart-on-corruption</literal> or
         <literal>--panic-on-corruption</literal> the kernel is restarted (panicked) immediately.

         (You have to provide way how to avoid restart loops.)</para></listitem>
       </varlistentry>

       <varlistentry>
         <term><option>ignore-zero-blocks</option></term>

         <listitem><para>Instruct kernel to not verify blocks that are expected to contain zeroes and always directly
         return zeroes instead.

         WARNING: Use this option only in very specific cases. This option is available since Linux kernel version 4.5.
         </para></listitem>
       </varlistentry>

       <varlistentry>
         <term><option>check-at-most-once</option></term>

         <listitem><para>Instruct kernel to verify blocks only the first time they are read from the data device, rather
         than every time.

         WARNING: It provides a reduced level of security because only offline tampering of the data device's content
         will be detected, not online tampering. This option is available since Linux kernel version 4.17.
         </para></listitem>
       </varlistentry>

       <varlistentry>
         <term><option>root-hash-signature=</option></term>

         <listitem><para>A base64 string encoding the root hash signature prefixed by <literal>base64:</literal> or a
         path to roothash signature file used to verify the root hash (in kernel). This feature requires Linux kernel
         version 5.4 or more recent.</para></listitem>
       </varlistentry>

       <varlistentry>
         <term><option>_netdev</option></term>

         <listitem><para>Marks this veritysetup device as requiring network. It will be
         started after the network is available, similarly to
         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
         units marked with <option>_netdev</option>. The service unit to set up this device
         will be ordered between <filename>remote-fs-pre.target</filename> and
         <filename>remote-veritysetup.target</filename>, instead of
         <filename>veritysetup-pre.target</filename> and
         <filename>veritysetup.target</filename>.</para>

         <para>Hint: if this device is used for a mount point that is specified in
         <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
         the <option>_netdev</option> option should also be used for the mount
         point. Otherwise, a dependency loop might be created where the mount point
         will be pulled in by <filename>local-fs.target</filename>, while the
         service to configure the network is usually only started <emphasis>after</emphasis>
         the local file system has been mounted.</para>
         </listitem>
       </varlistentry>

       <varlistentry>
         <term><option>noauto</option></term>

         <listitem><para>This device will not be added to <filename>veritysetup.target</filename>.
         This means that it will not be automatically enabled on boot, unless something else pulls
         it in. In particular, if the device is used for a mount point, it'll be enabled
         automatically during boot, unless the mount point itself is also disabled with
         <option>noauto</option>.</para></listitem>
       </varlistentry>

       <varlistentry>
         <term><option>nofail</option></term>

         <listitem><para>This device will not be a hard dependency of
         <filename>veritysetup.target</filename>. It'll still be pulled in and started, but the system
         will not wait for the device to show up and be enabled, and boot will not fail if this is
         unsuccessful. Note that other units that depend on the enabled device may still fail. In
         particular, if the device is used for a mount point, the mount point itself also needs to
         have the <option>nofail</option> option, or the boot will fail if the device is not enabled
         successfully.</para></listitem>
       </varlistentry>

       <varlistentry>
         <term><option>x-initrd.attach</option></term>

         <listitem><para>Setup this verity protected block device in the initramfs, similarly to
         <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
         units marked with <option>x-initrd.mount</option>.</para>

         <para>Although it's not necessary to mark the mount entry for the root file system with
         <option>x-initrd.mount</option>, <option>x-initrd.attach</option> is still recommended with
         the verity protected block device containing the root file system as otherwise systemd
         will attempt to detach the device during the regular system shutdown while it's still in
         use. With this option the device will still be detached but later after the root file
         system is unmounted.</para>

         <para>All other verity protected block devices that contain file systems mounted in the
         initramfs should use this option.</para>
         </listitem>
       </varlistentry>

     </variablelist>

     <para>At early boot and when the system manager configuration is
     reloaded, this file is translated into native systemd units by
     <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
   </refsect1>

   <refsect1>
     <title>Examples</title>
     <example>
       <title>/etc/veritytab example</title>
       <para>Set up two verity protected block devices. One using device blocks, another using files.</para>

       <programlisting>usr  PARTUUID=783e45ae-7aa3-484a-beef-a80ff9c19cbb PARTUUID=21dc1dfe-4c33-8b48-98a9-918a22eb3e37 36e3f740ad502e2c25e2a23d9c7c17bf0fdad2300b7580842d4b7ec1fb0fa263 auto
 data /etc/data /etc/hash a5ee4b42f70ae1f46a08a7c92c2e0a20672ad2f514792730f5d49d7606ab8fdf auto
 </programlisting>
     </example>
   </refsect1>

   <refsect1>
     <title>See Also</title>
     <para>
       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>systemd-veritysetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
       <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
       <citerefentry project='die-net'><refentrytitle>veritysetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
     </para>
   </refsect1>

 </refentry>
	<?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

	This is based on crypttab(5).

	-->
	<refentry id="veritytab" conditional='HAVE_LIBCRYPTSETUP' xmlns:xi="http://www.w3.org/2001/XInclude">

	<refentryinfo>
	<title>veritytab</title>
	<productname>systemd</productname>
	</refentryinfo>

	<refmeta>
	<refentrytitle>veritytab</refentrytitle>
	<manvolnum>5</manvolnum>
	</refmeta>

	<refnamediv>
	<refname>veritytab</refname>
	<refpurpose>Configuration for verity block devices</refpurpose>
	</refnamediv>

	<refsynopsisdiv>
	<para><filename>/etc/veritytab</filename></para>
	</refsynopsisdiv>

	<refsect1>
	<title>Description</title>

	<para>The <filename>/etc/veritytab</filename> file describes
	verity protected block devices that are set up during
	system boot.</para>

	<para>Empty lines and lines starting with the <literal>#</literal>
	character are ignored. Each of the remaining lines describes one
	verity protected block device. Fields are delimited by
	white space.</para>

	<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>
	The first four fields are mandatory, the remaining one is optional.</para>

	<para>The first field contains the name of the resulting verity volume; its block device is set up
	below <filename>/dev/mapper/</filename>.</para>

	<para>The second field contains a path to the underlying block data device, or a specification of a block device via
	<literal>UUID=</literal> followed by the UUID.</para>

	<para>The third field contains a path to the underlying block hash device, or a specification of a block device via
	<literal>UUID=</literal> followed by the UUID.</para>

	<para>The fourth field is the <literal>roothash</literal> in hexadecimal.</para>

	<para>The fifth field, if present, is a comma-delimited list of options. The following options are
	recognized:</para>

	<variablelist class='fstab-options'>

	<varlistentry>
	<term><option>ignore-corruption</option></term>
	<term><option>restart-on-corruption</option></term>
	<term><option>panic-on-corruption</option></term>

	<listitem><para>Defines what to do if a data verity problem is detected (data corruption). Without these
	options kernel fails the IO operation with I/O error. With <literal>--ignore-corruption</literal> option the
	corruption is only logged. With <literal>--restart-on-corruption</literal> or
	<literal>--panic-on-corruption</literal> the kernel is restarted (panicked) immediately.

	(You have to provide way how to avoid restart loops.)</para></listitem>
	</varlistentry>

	<varlistentry>
	<term><option>ignore-zero-blocks</option></term>

	<listitem><para>Instruct kernel to not verify blocks that are expected to contain zeroes and always directly
	return zeroes instead.

	WARNING: Use this option only in very specific cases. This option is available since Linux kernel version 4.5.
	</para></listitem>
	</varlistentry>

	<varlistentry>
	<term><option>check-at-most-once</option></term>

	<listitem><para>Instruct kernel to verify blocks only the first time they are read from the data device, rather
	than every time.

	WARNING: It provides a reduced level of security because only offline tampering of the data device's content
	will be detected, not online tampering. This option is available since Linux kernel version 4.17.
	</para></listitem>
	</varlistentry>

	<varlistentry>
	<term><option>root-hash-signature=</option></term>

	<listitem><para>A base64 string encoding the root hash signature prefixed by <literal>base64:</literal> or a
	path to roothash signature file used to verify the root hash (in kernel). This feature requires Linux kernel
	version 5.4 or more recent.</para></listitem>
	</varlistentry>

	<varlistentry>
	<term><option>_netdev</option></term>

	<listitem><para>Marks this veritysetup device as requiring network. It will be
	started after the network is available, similarly to
	<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
	units marked with <option>_netdev</option>. The service unit to set up this device
	will be ordered between <filename>remote-fs-pre.target</filename> and
	<filename>remote-veritysetup.target</filename>, instead of
	<filename>veritysetup-pre.target</filename> and
	<filename>veritysetup.target</filename>.</para>

	<para>Hint: if this device is used for a mount point that is specified in
	<citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
	the <option>_netdev</option> option should also be used for the mount
	point. Otherwise, a dependency loop might be created where the mount point
	will be pulled in by <filename>local-fs.target</filename>, while the
	service to configure the network is usually only started <emphasis>after</emphasis>
	the local file system has been mounted.</para>
	</listitem>
	</varlistentry>

	<varlistentry>
	<term><option>noauto</option></term>

	<listitem><para>This device will not be added to <filename>veritysetup.target</filename>.
	This means that it will not be automatically enabled on boot, unless something else pulls
	it in. In particular, if the device is used for a mount point, it'll be enabled
	automatically during boot, unless the mount point itself is also disabled with
	<option>noauto</option>.</para></listitem>
	</varlistentry>

	<varlistentry>
	<term><option>nofail</option></term>

	<listitem><para>This device will not be a hard dependency of
	<filename>veritysetup.target</filename>. It'll still be pulled in and started, but the system
	will not wait for the device to show up and be enabled, and boot will not fail if this is
	unsuccessful. Note that other units that depend on the enabled device may still fail. In
	particular, if the device is used for a mount point, the mount point itself also needs to
	have the <option>nofail</option> option, or the boot will fail if the device is not enabled
	successfully.</para></listitem>
	</varlistentry>

	<varlistentry>
	<term><option>x-initrd.attach</option></term>

	<listitem><para>Setup this verity protected block device in the initramfs, similarly to
	<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>
	units marked with <option>x-initrd.mount</option>.</para>

	<para>Although it's not necessary to mark the mount entry for the root file system with
	<option>x-initrd.mount</option>, <option>x-initrd.attach</option> is still recommended with
	the verity protected block device containing the root file system as otherwise systemd
	will attempt to detach the device during the regular system shutdown while it's still in
	use. With this option the device will still be detached but later after the root file
	system is unmounted.</para>

	<para>All other verity protected block devices that contain file systems mounted in the
	initramfs should use this option.</para>
	</listitem>
	</varlistentry>

	</variablelist>

	<para>At early boot and when the system manager configuration is
	reloaded, this file is translated into native systemd units by
	<citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
	</refsect1>

	<refsect1>
	<title>Examples</title>
	<example>
	<title>/etc/veritytab example</title>
	<para>Set up two verity protected block devices. One using device blocks, another using files.</para>

	<programlisting>usr PARTUUID=783e45ae-7aa3-484a-beef-a80ff9c19cbb PARTUUID=21dc1dfe-4c33-8b48-98a9-918a22eb3e37 36e3f740ad502e2c25e2a23d9c7c17bf0fdad2300b7580842d4b7ec1fb0fa263 auto
	data /etc/data /etc/hash a5ee4b42f70ae1f46a08a7c92c2e0a20672ad2f514792730f5d49d7606ab8fdf auto
	</programlisting>
	</example>
	</refsect1>

	<refsect1>
	<title>See Also</title>
	<para>
	<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
	<citerefentry><refentrytitle>systemd-veritysetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
	<citerefentry><refentrytitle>systemd-veritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
	<citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
	<citerefentry project='die-net'><refentrytitle>veritysetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
	</para>
	</refsect1>

	</refentry>