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diff --git a/man/veritytab.xml b/man/veritytab.xml new file mode 100644 index 0000000..bc9aa58 --- /dev/null +++ b/man/veritytab.xml @@ -0,0 +1,325 @@ +<?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>superblock=<replaceable>BOOL</replaceable></option></term> + + <listitem><para>Use dm-verity with or without permanent on-disk superblock.</para> + + <xi:include href="version-info.xml" xpointer="v254"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>format=<replaceable>NUMBER</replaceable></option></term> + + <listitem><para>Specifies the hash version type. Format type 0 is original Chrome OS version. Format type 1 is + modern version.</para> + + <xi:include href="version-info.xml" xpointer="v254"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>data-block-size=<replaceable>BYTES</replaceable></option></term> + + <listitem><para>Used block size for the data device. (Note kernel supports only page-size as maximum + here; Multiples of 512 bytes.) </para> + + <xi:include href="version-info.xml" xpointer="v254"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>hash-block-size=<replaceable>BYTES</replaceable></option></term> + + <listitem><para>Used block size for the hash device. (Note kernel supports only page-size as maximum + here; Multiples of 512 bytes.)</para> + + <xi:include href="version-info.xml" xpointer="v254"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>data-blocks=<replaceable>BLOCKS</replaceable></option></term> + + <listitem><para>Number of blocks of data device used in verification. If not specified, the whole device is + used.</para> + + <xi:include href="version-info.xml" xpointer="v254"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>hash-offset=<replaceable>BYTES</replaceable></option></term> + + <listitem><para>Offset of hash area/superblock on <literal>hash-device</literal>. (Multiples of 512 bytes.) + </para> + + <xi:include href="version-info.xml" xpointer="v254"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>salt=<replaceable>HEX</replaceable></option></term> + + <listitem><para>Salt used for format or verification. Format is a hexadecimal string; 256 bytes long maximum; + <literal>-</literal>is the special value for empty.</para> + + <xi:include href="version-info.xml" xpointer="v254"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>uuid=<replaceable>UUID</replaceable></option></term> + + <listitem><para>Use the provided UUID for format command instead of generating new one. The UUID must be + provided in standard UUID format, e.g. 12345678-1234-1234-1234-123456789abc.</para> + + <xi:include href="version-info.xml" xpointer="v254"/></listitem> + <listitem><para></para></listitem> + </varlistentry> + + <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> + + <xi:include href="version-info.xml" xpointer="v248"/></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> + + <xi:include href="version-info.xml" xpointer="v248"/></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> + + <xi:include href="version-info.xml" xpointer="v248"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>hash=<replaceable>HASH</replaceable></option></term> + + <listitem><para>Hash algorithm for dm-verity. This should be the name of the algorithm, like "sha1". For default + see <command>veritysetup --help</command>.</para> + + <xi:include href="version-info.xml" xpointer="v254"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>fec-device=<replaceable>PATH</replaceable></option></term> + + <listitem><para>Use forward error correction (FEC) to recover from corruption if hash verification fails. Use + encoding data from the specified device. The fec device argument can be block device or file image. For format, + if fec device path doesn't exist, it will be created as file. Note: block sizes for data and hash devices must + match. Also, if the verity data_device is encrypted the fec_device should be too.</para> + + <xi:include href="version-info.xml" xpointer="v254"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>fec-offset=<replaceable>BYTES</replaceable></option></term> + + <listitem><para>This is the offset, in bytes, from the start of the FEC device to the beginning of the encoding + data. (Aligned on 512 bytes.)</para> + + <xi:include href="version-info.xml" xpointer="v254"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>fec-roots=<replaceable>NUM</replaceable></option></term> + + <listitem><para>Number of generator roots. This equals to the number of parity bytes in the encoding data. In + RS(M, N) encoding, the number of roots is M-N. M is 255 and M-N is between 2 and 24 (including).</para> + + <xi:include href="version-info.xml" xpointer="v254"/> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>root-hash-signature=<replaceable>PATH</replaceable>|base64:<replaceable>HEX</replaceable></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> + + <xi:include href="version-info.xml" xpointer="v248"/></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> + + <xi:include href="version-info.xml" xpointer="v248"/> + </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> + + <xi:include href="version-info.xml" xpointer="v248"/></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> + + <xi:include href="version-info.xml" xpointer="v248"/></listitem> + </varlistentry> + + <varlistentry> + <term><option>x-initrd.attach</option></term> + + <listitem><para>Setup this verity protected block device in the initrd, 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 initrd should + use this option.</para> + + <xi:include href="version-info.xml" xpointer="v248"/> + </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> |