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188 lines
7.9 KiB
XML
188 lines
7.9 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/4.5/docbookx.dtd">
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<!--
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SPDX-License-Identifier: LGPL-2.1-or-later
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-->
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<refentry id="integritytab" conditional='HAVE_LIBCRYPTSETUP' xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>integritytab</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>integritytab</refentrytitle>
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<manvolnum>5</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>integritytab</refname>
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<refpurpose>Configuration for integrity block devices</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>/etc/integritytab</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/integritytab</filename> file describes
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integrity 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 integrity 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>block-device</replaceable>
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<replaceable>[keyfile|-]</replaceable> <replaceable>[options|-]</replaceable></programlisting>
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The first two fields are mandatory, the remaining two are optional and only required if user specified non-default options during integrity format.</para>
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<para>The first field contains the name of the resulting integrity 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 device, or a specification of a block device via
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<literal>UUID=</literal> followed by the UUID,
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<literal>PARTUUID=</literal> followed by the partition UUID,
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<literal>LABEL=</literal> followed by the label,
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<literal>PARTLABEL=</literal> followed by the partition label.
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</para>
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<para>The third field if present contains an absolute filename path to a key file or a <literal>-</literal>
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to specify none. When the filename is present, the "integrity-algorithm" defaults to <literal>hmac-sha256</literal>
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with the key length derived from the number of bytes in the key file. At this time the only supported integrity algorithm
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when using key file is hmac-sha256. The maximum size of the key file is 4096 bytes.
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</para>
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<para>The fourth field, if present, is a comma-delimited list of options or a <literal>-</literal> to specify none. The following options are
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recognized:</para>
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<variablelist>
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<varlistentry>
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<term><option>allow-discards</option></term>
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<listitem><para>
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Allow the use of discard (TRIM) requests for the device.
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This option is available since the Linux kernel version 5.7.
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</para>
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<xi:include href="version-info.xml" xpointer="v250"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>mode=(journal|bitmap|direct)</option></term>
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<listitem><para>
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Enable journaled, bitmapped or direct (passthrough) mode. Journaled mode is the default when this option is not specified.
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It provides safety against crashes, but can be slow because all data has to be written twice.
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Bitmap mode is more efficient since it requires only a single write, but it is less reliable because if data corruption happens when the machine crashes, it might not be detected.
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Direct mode disables the journal and the bitmap. Corresponds to the "direct writes" mode documented in
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<ulink url="https://docs.kernel.org/admin-guide/device-mapper/dm-integrity.html">the dm-integrity documentation</ulink>.
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Note that without a journal, if there is a crash, it is possible that the integrity tags and data will not match. If used, the journal-*
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options below will have no effect if passed.
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</para>
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<xi:include href="version-info.xml" xpointer="v254"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>journal-watermark=[0..100]%</option></term>
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<listitem><para>
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Journal watermark in percent. When the journal percentage exceeds this watermark, the journal flush will be started. Setting a value of
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"0%" uses default value.
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</para>
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<xi:include href="version-info.xml" xpointer="v250"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>journal-commit-time=[0..N]</option></term>
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<listitem><para>
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Commit time in milliseconds. When this time passes (and no explicit flush operation was issued), the journal is written. Setting a value of
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zero uses default value.
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</para>
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<xi:include href="version-info.xml" xpointer="v250"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>data-device=/dev/disk/by-...</option></term>
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<listitem><para>
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Specify a separate block device that contains existing data. The second field specified in the
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integritytab for block device then will contain calculated integrity tags and journal for data-device,
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but not the end user data.
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</para>
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<xi:include href="version-info.xml" xpointer="v250"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><option>integrity-algorithm=[crc32c|crc32|xxhash64|sha1|sha256|hmac-sha256]</option></term>
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<listitem><para>
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The algorithm used for integrity checking. The default is crc32c. Must match option used during format.
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</para>
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<xi:include href="version-info.xml" xpointer="v250"/></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-integritysetup-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/integritytab</title>
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<para>Set up two integrity protected block devices. </para>
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<programlisting>home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8 - journal-commit-time=10,allow-discards,journal-watermark=55%
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data PARTUUID=5d4b1808-be76-774d-88af-03c4c3a41761 - allow-discards
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</programlisting>
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</example>
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<example>
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<title>/etc/integritytab</title>
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<para>Set up 1 integrity protected block device using defaults </para>
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<programlisting>home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8</programlisting>
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</example>
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<example>
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<title>/etc/integritytab</title>
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<para>Set up 1 integrity device using existing data block device which contains user data </para>
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<programlisting>home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8 - data-device=/dev/disk/by-uuid/9276d9c0-d4e3-4297-b4ff-3307cd0d092f</programlisting>
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</example>
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<example>
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<title>/etc/integritytab</title>
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<para>Set up 1 integrity device using a HMAC key file using defaults </para>
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<programlisting>home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8 /etc/hmac.key</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><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-integritysetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>systemd-integritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
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<member><citerefentry project='die-net'><refentrytitle>integritysetup</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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