| <?xml version="1.0"?> |
| <!--*-nxml-*--> |
| <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
| <!-- |
| This file is part of systemd. |
| |
| Copyright 2012 Lennart Poettering |
| |
| systemd is free software; you can redistribute it and/or modify it |
| under the terms of the GNU Lesser General Public License as published by |
| the Free Software Foundation; either version 2.1 of the License, or |
| (at your option) any later version. |
| |
| systemd is distributed in the hope that it will be useful, but |
| WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public License |
| along with systemd; If not, see <http://www.gnu.org/licenses/>. |
| |
| This is based on crypttab(5) from Fedora's initscripts package, which in |
| turn is based on Debian's version. |
| |
| The Red Hat version has been written by Miloslav Trmac <mitr@redhat.com>. |
| |
| --> |
| <refentry id="crypttab" conditional='HAVE_LIBCRYPTSETUP'> |
| |
| <refentryinfo> |
| <title>crypttab</title> |
| <productname>systemd</productname> |
| |
| <authorgroup> |
| <author> |
| <contrib>Documentation</contrib> |
| <firstname>Miloslav</firstname> |
| <surname>Trmac</surname> |
| <email>mitr@redhat.com</email> |
| </author> |
| <author> |
| <contrib>Documentation</contrib> |
| <firstname>Lennart</firstname> |
| <surname>Poettering</surname> |
| <email>lennart@poettering.net</email> |
| </author> |
| </authorgroup> |
| </refentryinfo> |
| |
| <refmeta> |
| <refentrytitle>crypttab</refentrytitle> |
| <manvolnum>5</manvolnum> |
| </refmeta> |
| |
| <refnamediv> |
| <refname>crypttab</refname> |
| <refpurpose>Configuration for encrypted block devices</refpurpose> |
| </refnamediv> |
| |
| <refsynopsisdiv> |
| <para><filename>/etc/crypttab</filename></para> |
| </refsynopsisdiv> |
| |
| <refsect1> |
| <title>Description</title> |
| |
| <para>The <filename>/etc/crypttab</filename> file |
| describes encrypted 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 encrypted block device, fields on the |
| line are delimited by white space. The first two |
| fields are mandatory, the remaining two are |
| optional.</para> |
| |
| <para>Setting up encrypted block devices using this file |
| supports three encryption modes: LUKS, TrueCrypt and plain. |
| See <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
| for more information about each mode. When no mode is specified |
| in the options field and the block device contains a LUKS |
| signature, it is opened as a LUKS device; otherwise, it is |
| assumed to be in raw dm-crypt (plain mode) format.</para> |
| |
| <para>The first field contains the name of the |
| resulting encrypted block device; the device is set up |
| within <filename>/dev/mapper/</filename>.</para> |
| |
| <para>The second field contains a path to the |
| underlying block device or file, or a specification of a block |
| device via <literal>UUID=</literal> followed by the |
| UUID.</para> |
| |
| <para>The third field specifies the encryption |
| password. If the field is not present or the password |
| is set to <literal>none</literal> or <literal>-</literal>, |
| the password has to be manually entered during system boot. |
| Otherwise, the field is interpreted as a absolute path to |
| a file containing the encryption password. For swap encryption, |
| <filename>/dev/urandom</filename> or the hardware |
| device <filename>/dev/hw_random</filename> can be used |
| as the password file; using |
| <filename>/dev/random</filename> may prevent boot |
| completion if the system does not have enough entropy |
| to generate a truly random encryption key.</para> |
| |
| <para>The fourth field, if present, is a |
| comma-delimited list of options. The following |
| options are recognized:</para> |
| |
| <variablelist class='crypttab-options'> |
| |
| <varlistentry> |
| <term><varname>discard</varname></term> |
| |
| <listitem><para>Allow discard requests to be |
| passed through the encrypted block device. This |
| improves performance on SSD storage but has |
| security implications.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>cipher=</varname></term> |
| |
| <listitem><para>Specifies the cipher to use. See |
| <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
| for possible values and the default value of |
| this option. A cipher with unpredictable IV |
| values, such as <literal>aes-cbc-essiv:sha256</literal>, |
| is recommended.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>hash=</varname></term> |
| |
| <listitem><para>Specifies the hash to use for |
| password hashing. See |
| <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
| for possible values and the default value of |
| this option.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>keyfile-offset=</varname></term> |
| |
| <listitem><para>Specifies the number of bytes to |
| skip at the start of the key file. See |
| <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
| for possible values and the default value of |
| this option.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>keyfile-size=</varname></term> |
| |
| <listitem><para>Specifies the maximum number |
| of bytes to read from the key file. See |
| <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
| for possible values and the default value of |
| this option. This option is ignored in plain |
| encryption mode, as the key file size is then |
| given by the key size.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>key-slot=</varname></term> |
| |
| <listitem><para>Specifies the key slot to |
| compare the passphrase or key against. |
| If the key slot does not match the given |
| passphrase or key, but another would, the |
| setup of the device will fail regardless. |
| This option implies <varname>luks</varname>. See |
| <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
| for possible values. The default is to try |
| all key slots in sequential order.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>luks</varname></term> |
| |
| <listitem><para>Force LUKS mode. When this mode |
| is used, the following options are ignored since |
| they are provided by the LUKS header on the |
| device: <varname>cipher=</varname>, |
| <varname>hash=</varname>, |
| <varname>size=</varname>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>noauto</varname></term> |
| |
| <listitem><para>This device will not be |
| automatically unlocked on boot.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>nofail</varname></term> |
| |
| <listitem><para>The system will not wait for the |
| device to show up and be unlocked at boot, and |
| not fail the boot if it does not show up.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>plain</varname></term> |
| |
| <listitem><para>Force plain encryption mode.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>read-only</varname></term><term><varname>readonly</varname></term> |
| |
| <listitem><para>Set up the encrypted block |
| device in read-only mode.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>size=</varname></term> |
| |
| <listitem><para>Specifies the key size |
| in bits. See |
| <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
| for possible values and the default value of |
| this option.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>swap</varname></term> |
| |
| <listitem><para>The encrypted block device will |
| be used as a swap device, and will be formatted |
| accordingly after setting up the encrypted |
| block device, with |
| <citerefentry><refentrytitle>mkswap</refentrytitle><manvolnum>8</manvolnum></citerefentry>. |
| This option implies <varname>plain</varname>.</para> |
| |
| <para>WARNING: Using the <varname>swap</varname> |
| option will destroy the contents of the named |
| partition during every boot, so make sure the |
| underlying block device is specified correctly.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>tcrypt</varname></term> |
| |
| <listitem><para>Use TrueCrypt encryption mode. |
| When this mode is used, the following options are |
| ignored since they are provided by the TrueCrypt |
| header on the device or do not apply: |
| <varname>cipher=</varname>, |
| <varname>hash=</varname>, |
| <varname>keyfile-offset=</varname>, |
| <varname>keyfile-size=</varname>, |
| <varname>size=</varname>.</para> |
| |
| <para>When this mode is used, the passphrase is |
| read from the key file given in the third field. |
| Only the first line of this file is read, |
| excluding the new line character.</para> |
| |
| <para>Note that the TrueCrypt format uses both |
| passphrase and key files to derive a password |
| for the volume. Therefore, the passphrase and |
| all key files need to be provided. Use |
| <varname>tcrypt-keyfile=</varname> to provide |
| the absolute path to all key files. When using |
| an empty passphrase in combination with one or |
| more key files, use <literal>/dev/null</literal> |
| as the password file in the third field.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>tcrypt-hidden</varname></term> |
| |
| <listitem><para>Use the hidden TrueCrypt volume. |
| This option implies <varname>tcrypt</varname>.</para> |
| |
| <para>This will map the hidden volume that is |
| inside of the volume provided in the second |
| field. Please note that there is no protection |
| for the hidden volume if the outer volume is |
| mounted instead. See |
| <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
| for more information on this limitation.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>tcrypt-keyfile=</varname></term> |
| |
| <listitem><para>Specifies the absolute path to a |
| key file to use for a TrueCrypt volume. This |
| implies <varname>tcrypt</varname> and can be |
| used more than once to provide several key |
| files.</para> |
| |
| <para>See the entry for <varname>tcrypt</varname> |
| on the behavior of the passphrase and key files |
| when using TrueCrypt encryption mode.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>tcrypt-system</varname></term> |
| |
| <listitem><para>Use TrueCrypt in system |
| encryption mode. This option implies |
| <varname>tcrypt</varname>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>timeout=</varname></term> |
| |
| <listitem><para>Specifies the timeout for |
| querying for a password. If no unit is |
| specified, seconds is used. Supported units are |
| s, ms, us, min, h, d. A timeout of 0 waits |
| indefinitely (which is the default).</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>tmp</varname></term> |
| |
| <listitem><para>The encrypted block device will |
| be prepared for using it as <filename>/tmp</filename>; |
| it will be formatted using |
| <citerefentry><refentrytitle>mke2fs</refentrytitle><manvolnum>8</manvolnum></citerefentry>. |
| This option implies <varname>plain</varname>.</para> |
| |
| <para>WARNING: Using the <varname>tmp</varname> |
| option will destroy the contents of the named |
| partition during every boot, so make sure the |
| underlying block device is specified correctly.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>tries=</varname></term> |
| |
| <listitem><para>Specifies the maximum number of |
| times the user is queried for a password. |
| The default is 3. If set to 0, the user is |
| queried for a password indefinitely.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><varname>verify</varname></term> |
| |
| <listitem><para> If the encryption password is |
| read from console, it has to be entered twice to |
| prevent typos.</para></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-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para> |
| </refsect1> |
| |
| <refsect1> |
| <title>Example</title> |
| <example> |
| <title>/etc/crypttab example</title> |
| <para>Set up four encrypted block devices. One using |
| LUKS for normal storage, another one for usage as a swap |
| device and two TrueCrypt volumes.</para> |
| |
| <programlisting>luks UUID=2505567a-9e27-4efe-a4d5-15ad146c258b |
| swap /dev/sda7 /dev/urandom swap |
| truecrypt /dev/sda2 /etc/container_password tcrypt |
| hidden /mnt/tc_hidden /null tcrypt-hidden,tcrypt-keyfile=/etc/keyfile</programlisting> |
| </example> |
| </refsect1> |
| |
| <refsect1> |
| <title>See Also</title> |
| <para> |
| <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>mkswap</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>mke2fs</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
| </para> |
| </refsect1> |
| |
| </refentry> |