man/systemd-cryptsetup-generator.xml

   1 <?xml version="1.0"?>
   2 <!--*-nxml-*-->
   3 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   4   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   5 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
   6 <refentry id="systemd-cryptsetup-generator" conditional='HAVE_LIBCRYPTSETUP'
   7           xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>systemd-cryptsetup-generator</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>systemd-cryptsetup-generator</refentrytitle>
  16     <manvolnum>8</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>systemd-cryptsetup-generator</refname>
  21     <refpurpose>Unit generator for <filename>/etc/crypttab</filename></refpurpose>
  22   </refnamediv>
  23
  24   <refsynopsisdiv>
  25     <para><filename>/usr/lib/systemd/system-generators/systemd-cryptsetup-generator</filename></para>
  26   </refsynopsisdiv>
  27
  28   <refsect1>
  29     <title>Description</title>
  30
  31     <para><filename>systemd-cryptsetup-generator</filename> is a
  32     generator that translates <filename>/etc/crypttab</filename> into
  33     native systemd units early at boot and when configuration of the
  34     system manager is reloaded. This will create
  35     <citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  36     units as necessary.</para>
  37
  38     <para><filename>systemd-cryptsetup-generator</filename> implements
  39     <citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
  40   </refsect1>
  41
  42   <refsect1>
  43     <title>Kernel Command Line</title>
  44
  45     <para><filename>systemd-cryptsetup-generator</filename>
  46     understands the following kernel command line parameters:</para>
  47
  48     <variablelist class='kernel-commandline-options'>
  49       <varlistentry>
  50         <term><varname>luks=</varname></term>
  51         <term><varname>rd.luks=</varname></term>
  52
  53         <listitem><para>Takes a boolean argument. Defaults to <literal>yes</literal>. If
  54         <literal>no</literal>, disables the generator entirely. <varname>rd.luks=</varname> is honored only
  55         in the initrd while <varname>luks=</varname> is honored by both the main system and in the initrd.
  56         </para></listitem>
  57       </varlistentry>
  58
  59       <varlistentry>
  60         <term><varname>luks.crypttab=</varname></term>
  61         <term><varname>rd.luks.crypttab=</varname></term>
  62
  63         <listitem><para>Takes a boolean argument. Defaults to <literal>yes</literal>. If
  64         <literal>no</literal>, causes the generator to ignore any devices configured in
  65         <filename>/etc/crypttab</filename> (<varname>luks.uuid=</varname> will still work however).
  66         <varname>rd.luks.crypttab=</varname> is honored only in initrd while
  67         <varname>luks.crypttab=</varname> is honored by both the main system and in the initrd.
  68         </para></listitem>
  69       </varlistentry>
  70
  71       <varlistentry>
  72         <term><varname>luks.uuid=</varname></term>
  73         <term><varname>rd.luks.uuid=</varname></term>
  74
  75         <listitem><para>Takes a LUKS superblock UUID as argument. This will activate the specified device as
  76         part of the boot process as if it was listed in <filename>/etc/crypttab</filename>. This option may
  77         be specified more than once in order to set up multiple devices. <varname>rd.luks.uuid=</varname> is
  78         honored only in the initrd, while <varname>luks.uuid=</varname> is honored by both the main system
  79         and in the initrd.</para>
  80
  81         <para>If <filename>/etc/crypttab</filename> contains entries with the same UUID, then the name,
  82         keyfile and options specified there will be used. Otherwise, the device will have the name
  83         <literal>luks-UUID</literal>.</para>
  84
  85         <para>If <filename>/etc/crypttab</filename> exists, only those UUIDs specified on the kernel command
  86         line will be activated in the initrd or the real root.</para>
  87         </listitem>
  88       </varlistentry>
  89
  90       <varlistentry>
  91         <term><varname>luks.name=</varname></term>
  92         <term><varname>rd.luks.name=</varname></term>
  93
  94         <listitem><para>Takes a LUKS super block UUID followed by an
  95         <literal>=</literal> and a name. This implies
  96         <varname>rd.luks.uuid=</varname> or
  97         <varname>luks.uuid=</varname> and will additionally make the
  98         LUKS device given by the UUID appear under the provided
  99         name.</para>
 100
 101         <para>This parameter is the analogue of the first <citerefentry><refentrytitle>crypttab</refentrytitle>
 102         <manvolnum>5</manvolnum></citerefentry> field <replaceable>volume-name</replaceable>.</para>
 103
 104         <para><varname>rd.luks.name=</varname> is honored only in the initrd, while
 105         <varname>luks.name=</varname> is honored by both the main system and in the initrd.</para>
 106         </listitem>
 107       </varlistentry>
 108
 109       <varlistentry>
 110         <term><varname>luks.data=</varname></term>
 111         <term><varname>rd.luks.data=</varname></term>
 112
 113         <listitem><para>Takes a LUKS super block UUID followed by a <literal>=</literal> and a block device
 114         specification for device hosting encrypted data.</para>
 115
 116         <para>For those entries specified with <varname>rd.luks.uuid=</varname> or
 117         <varname>luks.uuid=</varname>, the data device will be set to the one specified by
 118         <varname>rd.luks.data=</varname> or <varname>luks.data=</varname> of the corresponding UUID.</para>
 119
 120         <para>LUKS data device parameter is useful for specifying encrypted data devices with detached headers specified in
 121         <varname>luks.options</varname> entry containing <literal>header=</literal> argument. For example,
 122         <varname>rd.luks.uuid=</varname>b40f1abf-2a53-400a-889a-2eccc27eaa40
 123         <varname>rd.luks.options=</varname>b40f1abf-2a53-400a-889a-2eccc27eaa40=header=/path/to/luks.hdr
 124         <varname>rd.luks.data=</varname>b40f1abf-2a53-400a-889a-2eccc27eaa40=/dev/sdx.
 125         Hence, in this case, we will attempt to unlock LUKS device assembled from data device <literal>/dev/sdx</literal>
 126         and LUKS header (metadata) put in <literal>/path/to/luks.hdr</literal> file. This syntax is for now
 127         only supported on a per-device basis, i.e. you have to specify LUKS device UUID.</para>
 128
 129         <para>This parameter is the analogue of the second <citerefentry><refentrytitle>crypttab</refentrytitle>
 130         <manvolnum>5</manvolnum></citerefentry> field <replaceable>encrypted-device</replaceable>.</para>
 131
 132         <para><varname>rd.luks.data=</varname> is honored only in the initrd, while
 133         <varname>luks.data=</varname> is honored by both the main system and in the initrd.</para>
 134         </listitem>
 135       </varlistentry>
 136
 137       <varlistentry>
 138         <term><varname>luks.key=</varname></term>
 139         <term><varname>rd.luks.key=</varname></term>
 140
 141         <listitem><para>Takes a password file name as argument or a
 142         LUKS super block UUID followed by a <literal>=</literal> and a
 143         password file name.</para>
 144
 145         <para>For those entries specified with
 146         <varname>rd.luks.uuid=</varname> or
 147         <varname>luks.uuid=</varname>, the password file will be set
 148         to the one specified by <varname>rd.luks.key=</varname> or
 149         <varname>luks.key=</varname> of the corresponding UUID, or the
 150         password file that was specified without a UUID.</para>
 151
 152         <para>It is also possible to specify an external device which
 153         should be mounted before we attempt to unlock the LUKS device.
 154         systemd-cryptsetup will use password file stored on that
 155         device. Device containing password file is specified by
 156         appending colon and a device identifier to the password file
 157         path. For example,
 158         <varname>rd.luks.uuid=</varname>b40f1abf-2a53-400a-889a-2eccc27eaa40
 159         <varname>rd.luks.key=</varname>b40f1abf-2a53-400a-889a-2eccc27eaa40=/keyfile:LABEL=keydev.
 160         Hence, in this case, we will attempt to mount file system
 161         residing on the block device with label <literal>keydev</literal>.
 162         This syntax is for now only supported on a per-device basis,
 163         i.e. you have to specify LUKS device UUID.</para>
 164
 165         <para>This parameter is the analogue of the third <citerefentry><refentrytitle>crypttab</refentrytitle>
 166         <manvolnum>5</manvolnum></citerefentry> field <replaceable>key-file</replaceable>.</para>
 167
 168         <para><varname>rd.luks.key=</varname> is honored only in the initrd, while
 169         <varname>luks.key=</varname> is honored by both the main system and in the initrd.</para>
 170         </listitem>
 171       </varlistentry>
 172
 173       <varlistentry>
 174         <term><varname>luks.options=</varname></term>
 175         <term><varname>rd.luks.options=</varname></term>
 176
 177         <listitem><para>Takes a LUKS super block UUID followed by an
 178         <literal>=</literal> and a string of options separated by
 179         commas as argument. This will override the options for the
 180         given UUID.</para>
 181         <para>If only a list of options, without a UUID, is
 182         specified, they apply to any UUIDs not specified elsewhere,
 183         and without an entry in
 184         <filename>/etc/crypttab</filename>.</para>
 185
 186         <para>This parameter is the analogue of the fourth <citerefentry><refentrytitle>crypttab</refentrytitle>
 187         <manvolnum>5</manvolnum></citerefentry> field <replaceable>options</replaceable>.</para>
 188
 189         <para>It is possible to specify an external device which
 190         should be mounted before we attempt to unlock the LUKS device.
 191         systemd-cryptsetup will assemble LUKS device by combining
 192         data device specified in <varname>luks.data</varname> with
 193         detached LUKS header found in <literal>header=</literal>
 194         argument. For example,
 195         <varname>rd.luks.uuid=</varname>b40f1abf-2a53-400a-889a-2eccc27eaa40
 196         <varname>rd.luks.options=</varname>b40f1abf-2a53-400a-889a-2eccc27eaa40=header=/luks.hdr:LABEL=hdrdev
 197         <varname>rd.luks.data=</varname>b40f1abf-2a53-400a-889a-2eccc27eaa40=/dev/sdx.
 198         Hence, in this case, we will attempt to mount file system
 199         residing on the block device with label <literal>hdrdev</literal>, and look
 200         for <literal>luks.hdr</literal> on that file system. Said header will be used
 201         to unlock (decrypt) encrypted data stored on /dev/sdx.
 202         This syntax is for now only supported on a per-device basis,
 203         i.e. you have to specify LUKS device UUID.</para>
 204
 205         <para><varname>rd.luks.options=</varname> is honored only by initial
 206         RAM disk (initrd) while <varname>luks.options=</varname> is
 207         honored by both the main system and in the initrd.</para>
 208         </listitem>
 209       </varlistentry>
 210     </variablelist>
 211   </refsect1>
 212
 213   <refsect1>
 214     <title>See Also</title>
 215     <para>
 216       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 217       <citerefentry><refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 218       <citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 219       <citerefentry><refentrytitle>systemd-cryptenroll</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 220       <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 221       <citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 222     </para>
 223   </refsect1>
 224
 225 </refentry>