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diff --git a/man/crypttab.xml b/man/crypttab.xml new file mode 100644 index 0000000..3574ce0 --- /dev/null +++ b/man/crypttab.xml @@ -0,0 +1,437 @@ +<?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"> +<!-- + SPDX-License-Identifier: LGPL-2.1+ + + 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> + </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 are delimited by white space.</para> + + <para>Each line is in the form<programlisting><replaceable>name</replaceable> <replaceable>encrypted-device</replaceable> <replaceable>password</replaceable> <replaceable>options</replaceable></programlisting> + 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 project='die-net'><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 an 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='fstab-options'> + + <varlistentry> + <term><option>cipher=</option></term> + + <listitem><para>Specifies the cipher to use. See + <citerefentry project='die-net'><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><option>discard</option></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><option>hash=</option></term> + + <listitem><para>Specifies the hash to use for password + hashing. See + <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> + for possible values and the default value of this + option.</para></listitem> + </varlistentry> + + <varlistentry> + <term><option>header=</option></term> + + <listitem><para>Use a detached (separated) metadata device or + file where the LUKS header is stored. This option is only + relevant for LUKS devices. See + <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> + for possible values and the default value of this + option.</para></listitem> + </varlistentry> + + <varlistentry> + <term><option>keyfile-offset=</option></term> + + <listitem><para>Specifies the number of bytes to skip at the + start of the key file. See + <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> + for possible values and the default value of this + option.</para></listitem> + </varlistentry> + + <varlistentry> + <term><option>keyfile-size=</option></term> + + <listitem><para>Specifies the maximum number of bytes to read + from the key file. See + <citerefentry project='die-net'><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><option>key-slot=</option></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 + <option>luks</option>. See + <citerefentry project='die-net'><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><option>luks</option></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: <option>cipher=</option>, + <option>hash=</option>, + <option>size=</option>.</para></listitem> + </varlistentry> + + <varlistentry> + <term><option>_netdev</option></term> + + <listitem><para>Marks this cryptsetup device as requiring network. It will be + started after the network is available, similarly to + <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry> + units marked with <option>_netdev</option>. The service unit to set up this device + will be ordered between <filename>remote-fs-pre.target</filename> and + <filename>remote-cryptsetup.target</filename>, instead of + <filename>cryptsetup-pre.target</filename> and + <filename>cryptsetup.target</filename>.</para> + + <para>Hint: if this device is used for a mount point that is specified in + <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + the <option>_netdev</option> option should also be used for the mount + point. Otherwise, a dependency loop might be created where the mount point + will be pulled in by <filename>local-fs.target</filename>, while the + service to configure the network is usually only started <emphasis>after</emphasis> + the local file system has been mounted.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>noauto</option></term> + + <listitem><para>This device will not be added to <filename>cryptsetup.target</filename>. + This means that it will not be automatically unlocked on boot, unless something else pulls + it in. In particular, if the device is used for a mount point, it'll be unlocked + automatically during boot, unless the mount point itself is also disabled with + <option>noauto</option>.</para></listitem> + </varlistentry> + + <varlistentry> + <term><option>nofail</option></term> + + <listitem><para>This device will not be a hard dependency of + <filename>cryptsetup.target</filename>. It'll be still pulled in and started, but the system + will not wait for the device to show up and be unlocked, and boot will not fail if this is + unsuccessful. Note that other units that depend on the unlocked device may still fail. In + particular, if the device is used for a mount point, the mount point itself is also needs to + have <option>noauto</option> option, or the boot will fail if the device is not unlocked + successfully.</para></listitem> + </varlistentry> + + <varlistentry> + <term><option>offset=</option></term> + + <listitem><para>Start offset in the backend device, in 512-byte sectors. This + option is only relevant for plain devices.</para></listitem> + </varlistentry> + + <varlistentry> + <term><option>plain</option></term> + + <listitem><para>Force plain encryption mode.</para></listitem> + </varlistentry> + + <varlistentry> + <term><option>read-only</option></term><term><option>readonly</option></term> + + <listitem><para>Set up the encrypted block device in read-only + mode.</para></listitem> + </varlistentry> + + <varlistentry> + <term><option>skip=</option></term> + + <listitem><para>How many 512-byte sectors of the encrypted data to skip at the + beginning. This is different from the <option>offset=</option> option with respect + to the sector numbers used in initialization vector (IV) calculation. Using + <option>offset=</option> will shift the IV calculation by the same negative + amount. Hence, if <option>offset=<replaceable>n</replaceable></option> is given, + sector <replaceable>n</replaceable> will get a sector number of 0 for the IV + calculation. Using <option>skip=</option> causes sector + <replaceable>n</replaceable> to also be the first sector of the mapped device, but + with its number for IV generation being <replaceable>n</replaceable>.</para> + + <para>This option is only relevant for plain devices.</para> + </listitem> + </varlistentry> + + <varlistentry> + <term><option>size=</option></term> + + <listitem><para>Specifies the key size in bits. See + <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> + for possible values and the default value of this + option.</para></listitem> + </varlistentry> + + <varlistentry> + <term><option>sector-size=</option></term> + + <listitem><para>Specifies the sector size in bytes. See + <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> + for possible values and the default value of this + option.</para></listitem> + </varlistentry> + + <varlistentry> + <term><option>swap</option></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 project='man-pages'><refentrytitle>mkswap</refentrytitle><manvolnum>8</manvolnum></citerefentry>. + This option implies <option>plain</option>.</para> + + <para>WARNING: Using the <option>swap</option> 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><option>tcrypt</option></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: + <option>cipher=</option>, + <option>hash=</option>, + <option>keyfile-offset=</option>, + <option>keyfile-size=</option>, + <option>size=</option>.</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 + <option>tcrypt-keyfile=</option> 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><option>tcrypt-hidden</option></term> + + <listitem><para>Use the hidden TrueCrypt volume. This option + implies <option>tcrypt</option>.</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 project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> + for more information on this limitation.</para></listitem> + </varlistentry> + + <varlistentry> + <term><option>tcrypt-keyfile=</option></term> + + <listitem><para>Specifies the absolute path to a key file to + use for a TrueCrypt volume. This implies + <option>tcrypt</option> and can be used more than once to + provide several key files.</para> + + <para>See the entry for <option>tcrypt</option> on the + behavior of the passphrase and key files when using TrueCrypt + encryption mode.</para></listitem> + </varlistentry> + + <varlistentry> + <term><option>tcrypt-system</option></term> + + <listitem><para>Use TrueCrypt in system encryption mode. This + option implies <option>tcrypt</option>.</para></listitem> + </varlistentry> + + <varlistentry> + <term><option>tcrypt-veracrypt</option></term> + + <listitem><para>Check for a VeraCrypt volume. VeraCrypt is a fork of + TrueCrypt that is mostly compatible, but uses different, stronger key + derivation algorithms that cannot be detected without this flag. + Enabling this option could substantially slow down unlocking, because + VeraCrypt's key derivation takes much longer than TrueCrypt's. This + option implies <option>tcrypt</option>.</para></listitem> + </varlistentry> + + <varlistentry> + <term><option>timeout=</option></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><option>tmp</option></term> + + <listitem><para>The encrypted block device will be prepared + for using it as <filename>/tmp</filename>; it will be + formatted using + <citerefentry project='man-pages'><refentrytitle>mke2fs</refentrytitle><manvolnum>8</manvolnum></citerefentry>. + This option implies <option>plain</option>.</para> + + <para>WARNING: Using the <option>tmp</option> 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><option>tries=</option></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><option>verify</option></term> + + <listitem><para> If the encryption password is read from + console, it has to be entered twice to prevent + typos.</para></listitem> + </varlistentry> + + <varlistentry> + <term><option>x-systemd.device-timeout=</option></term> + + <listitem><para>Specifies how long systemd should wait for a device to show up + before giving up on the entry. The argument is a time in seconds or explicitly + specified units of + <literal>s</literal>, + <literal>min</literal>, + <literal>h</literal>, + <literal>ms</literal>. + </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 /dev/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 project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>mkswap</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>mke2fs</refentrytitle><manvolnum>8</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |