man/integritytab.xml

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   9 <refentry id="integritytab" conditional='HAVE_LIBCRYPTSETUP' xmlns:xi="http://www.w3.org/2001/XInclude">
  10
  11   <refentryinfo>
  12     <title>integritytab</title>
  13     <productname>systemd</productname>
  14   </refentryinfo>
  15
  16   <refmeta>
  17     <refentrytitle>integritytab</refentrytitle>
  18     <manvolnum>5</manvolnum>
  19   </refmeta>
  20
  21   <refnamediv>
  22     <refname>integritytab</refname>
  23     <refpurpose>Configuration for integrity block devices</refpurpose>
  24   </refnamediv>
  25
  26   <refsynopsisdiv>
  27     <para><filename>/etc/integritytab</filename></para>
  28   </refsynopsisdiv>
  29
  30   <refsect1>
  31     <title>Description</title>
  32
  33     <para>The <filename>/etc/integritytab</filename> file describes
  34     integrity protected block devices that are set up during
  35     system boot.</para>
  36
  37     <para>Empty lines and lines starting with the <literal>#</literal>
  38     character are ignored. Each of the remaining lines describes one
  39     verity integrity protected block device. Fields are delimited by
  40     white space.</para>
  41
  42     <para>Each line is in the form<programlisting><replaceable>volume-name</replaceable> <replaceable>block-device</replaceable>
  43     <replaceable>[keyfile|-]</replaceable> <replaceable>[options|-]</replaceable></programlisting>
  44     The first two fields are mandatory, the remaining two are optional and only required if user specified non-default options during integrity format.</para>
  45
  46     <para>The first field contains the name of the resulting integrity volume; its block device is set up
  47     below <filename>/dev/mapper/</filename>.</para>
  48
  49     <para>The second field contains a path to the underlying block device, or a specification of a block device via
  50     <literal>UUID=</literal> followed by the UUID,
  51     <literal>PARTUUID=</literal> followed by the partition UUID,
  52     <literal>LABEL=</literal> followed by the label,
  53     <literal>PARTLABEL=</literal> followed by the partition label.
  54     </para>
  55
  56     <para>The third field if present contains an absolute filename path to a key file or a <literal>-</literal>
  57     to specify none.  When the filename is present, the "integrity-algorithm" defaults to <literal>hmac-sha256</literal>
  58     with the key length derived from the number of bytes in the key file.  At this time the only supported integrity algorithm
  59     when using key file is hmac-sha256.  The maximum size of the key file is 4096 bytes.
  60     </para>
  61
  62      <para>The fourth field, if present, is a comma-delimited list of options or a <literal>-</literal> to specify none. The following options are
  63     recognized:</para>
  64       <variablelist>
  65
  66       <varlistentry>
  67         <term><option>allow-discards</option></term>
  68
  69         <listitem><para>
  70         Allow the use of discard (TRIM) requests for the device.
  71         This option is available since the Linux kernel version 5.7.
  72         </para>
  73
  74         <xi:include href="version-info.xml" xpointer="v250"/></listitem>
  75       </varlistentry>
  76
  77       <varlistentry>
  78         <term><option>mode=(journal|bitmap|direct)</option></term>
  79
  80         <listitem><para>
  81         Enable journaled, bitmapped or direct (passthrough) mode. Journaled mode is the default when this option is not specified.
  82         It provides safety against crashes, but can be slow because all data has to be written twice.
  83         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 may not be detected.
  84         Direct mode disables the journal and the bitmap. Corresponds to the "direct writes" mode documented in
  85         <ulink url="https://docs.kernel.org/admin-guide/device-mapper/dm-integrity.html">the dm-integrity documentation</ulink>.
  86         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-*
  87         options below will have no effect if passed.
  88         </para>
  89
  90         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
  91       </varlistentry>
  92
  93       <varlistentry>
  94         <term><option>journal-watermark=[0..100]%</option></term>
  95
  96         <listitem><para>
  97         Journal watermark in percent. When the journal percentage exceeds this watermark, the journal flush will be started.  Setting a value of
  98         "0%" uses default value.
  99         </para>
 100
 101         <xi:include href="version-info.xml" xpointer="v250"/></listitem>
 102       </varlistentry>
 103
 104       <varlistentry>
 105         <term><option>journal-commit-time=[0..N]</option></term>
 106
 107         <listitem><para>
 108         Commit time in milliseconds. When this time passes (and no explicit flush operation was issued), the journal is written.  Setting a value of
 109         zero uses default value.
 110         </para>
 111
 112         <xi:include href="version-info.xml" xpointer="v250"/></listitem>
 113       </varlistentry>
 114
 115       <varlistentry>
 116         <term><option>data-device=/dev/disk/by-...</option></term>
 117
 118         <listitem><para>
 119         Specify a separate block device that contains existing data. The second field specified in the
 120         integritytab for block device then will contain calculated integrity tags and journal for data-device,
 121         but not the end user data.
 122         </para>
 123
 124         <xi:include href="version-info.xml" xpointer="v250"/></listitem>
 125       </varlistentry>
 126
 127       <varlistentry>
 128         <term><option>integrity-algorithm=[crc32c|crc32|sha1|sha256|hmac-sha256]</option></term>
 129
 130         <listitem><para>
 131         The algorithm used for integrity checking.  The default is crc32c. Must match option used during format.
 132         </para>
 133
 134         <xi:include href="version-info.xml" xpointer="v250"/></listitem>
 135       </varlistentry>
 136     </variablelist>
 137
 138     <para>At early boot and when the system manager configuration is
 139     reloaded, this file is translated into native systemd units by
 140     <citerefentry><refentrytitle>systemd-integritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 141   </refsect1>
 142
 143   <refsect1>
 144     <title>Examples</title>
 145     <example>
 146       <title>/etc/integritytab</title>
 147       <para>Set up two integrity protected block devices. </para>
 148
 149       <programlisting>home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8 - journal-commit-time=10,allow-discards,journal-watermark=55%
 150 data PARTUUID=5d4b1808-be76-774d-88af-03c4c3a41761 - allow-discards
 151 </programlisting>
 152     </example>
 153
 154     <example>
 155       <title>/etc/integritytab</title>
 156       <para>Set up 1 integrity protected block device using defaults </para>
 157
 158       <programlisting>home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8</programlisting>
 159     </example>
 160
 161     <example>
 162       <title>/etc/integritytab</title>
 163       <para>Set up 1 integrity device using existing data block device which contains user data </para>
 164
 165       <programlisting>home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8 - data-device=/dev/disk/by-uuid/9276d9c0-d4e3-4297-b4ff-3307cd0d092f</programlisting>
 166     </example>
 167
 168     <example>
 169       <title>/etc/integritytab</title>
 170       <para>Set up 1 integrity device using a HMAC key file using defaults </para>
 171
 172       <programlisting>home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8 /etc/hmac.key</programlisting>
 173     </example>
 174
 175   </refsect1>
 176
 177   <refsect1>
 178     <title>See Also</title>
 179     <para>
 180       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 181       <citerefentry><refentrytitle>systemd-integritysetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 182       <citerefentry><refentrytitle>systemd-integritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 183       <citerefentry project='die-net'><refentrytitle>integritysetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 184     </para>
 185   </refsect1>
 186
 187 </refentry>