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></listitem>
  73       </varlistentry>
  74
  75       <varlistentry>
  76         <term><option>mode=(journal|bitmap|direct)</option></term>
  77
  78         <listitem><para>
  79         Enable journaled, bitmapped or direct (passthrough) mode. Journaled mode is the default when this option is not specified.
  80         It provides safety against crashes, but can be slow because all data has to be written twice.
  81         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.
  82         Direct mode disables the journal and the bitmap. Corresponds to the "direct writes" mode documented in
  83         <ulink url="https://docs.kernel.org/admin-guide/device-mapper/dm-integrity.html">the dm-integrity documentation</ulink>.
  84         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-*
  85         options below will have no effect if passed.
  86         </para></listitem>
  87       </varlistentry>
  88
  89       <varlistentry>
  90         <term><option>journal-watermark=[0..100]%</option></term>
  91
  92         <listitem><para>
  93         Journal watermark in percent. When the journal percentage exceeds this watermark, the journal flush will be started.  Setting a value of
  94         "0%" uses default value.
  95         </para></listitem>
  96       </varlistentry>
  97
  98       <varlistentry>
  99         <term><option>journal-commit-time=[0..N]</option></term>
 100
 101         <listitem><para>
 102         Commit time in milliseconds. When this time passes (and no explicit flush operation was issued), the journal is written.  Setting a value of
 103         zero uses default value.
 104         </para></listitem>
 105       </varlistentry>
 106
 107       <varlistentry>
 108         <term><option>data-device=/dev/disk/by-...</option></term>
 109
 110         <listitem><para>
 111         Specify a separate block device that contains existing data. The second field specified in the
 112         integritytab for block device then will contain calculated integrity tags and journal for data-device,
 113         but not the end user data.
 114         </para></listitem>
 115       </varlistentry>
 116
 117       <varlistentry>
 118         <term><option>integrity-algorithm=[crc32c|crc32|sha1|sha256|hmac-sha256]</option></term>
 119
 120         <listitem><para>
 121         The algorithm used for integrity checking.  The default is crc32c. Must match option used during format.
 122         </para></listitem>
 123       </varlistentry>
 124     </variablelist>
 125
 126     <para>At early boot and when the system manager configuration is
 127     reloaded, this file is translated into native systemd units by
 128     <citerefentry><refentrytitle>systemd-integritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 129   </refsect1>
 130
 131   <refsect1>
 132     <title>Examples</title>
 133     <example>
 134       <title>/etc/integritytab</title>
 135       <para>Set up two integrity protected block devices. </para>
 136
 137       <programlisting>home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8 - journal-commit-time=10,allow-discards,journal-watermark=55%
 138 data PARTUUID=5d4b1808-be76-774d-88af-03c4c3a41761 - allow-discards
 139 </programlisting>
 140     </example>
 141
 142     <example>
 143       <title>/etc/integritytab</title>
 144       <para>Set up 1 integrity protected block device using defaults </para>
 145
 146       <programlisting>home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8</programlisting>
 147     </example>
 148
 149     <example>
 150       <title>/etc/integritytab</title>
 151       <para>Set up 1 integrity device using existing data block device which contains user data </para>
 152
 153       <programlisting>home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8 - data-device=/dev/disk/by-uuid/9276d9c0-d4e3-4297-b4ff-3307cd0d092f</programlisting>
 154     </example>
 155
 156     <example>
 157       <title>/etc/integritytab</title>
 158       <para>Set up 1 integrity device using a HMAC key file using defaults </para>
 159
 160       <programlisting>home PARTUUID=4973d0b8-1b15-c449-96ec-94bab7f6a7b8 /etc/hmac.key</programlisting>
 161     </example>
 162
 163   </refsect1>
 164
 165   <refsect1>
 166     <title>See Also</title>
 167     <para>
 168       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 169       <citerefentry><refentrytitle>systemd-integritysetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 170       <citerefentry><refentrytitle>systemd-integritysetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 171       <citerefentry project='die-net'><refentrytitle>integritysetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 172     </para>
 173   </refsect1>
 174
 175 </refentry>