Systemd/man/systemd-cryptsetup-generator.xml
Michal Sekletar 70f5f48eb8 cryptsetup-generator: introduce basic keydev support
Dracut has a support for unlocking encrypted drives with keyfile stored
on the external drive. This support is included in the generated initrd
only if systemd module is not included.

When systemd is used in initrd then attachment of encrypted drives is
handled by systemd-cryptsetup tools. Our generator has support for
keyfile, however, it didn't support keyfile on the external block
device (keydev).

This commit introduces basic keydev support. Keydev can be specified per
luks.uuid on the kernel command line. Keydev is automatically mounted
during boot and we look for keyfile in the keydev
mountpoint (i.e. keyfile path is prefixed with the keydev mount point
path). After crypt device is attached we automatically unmount
where keyfile resides.

Example:
        rd.luks.key=70bc876b-f627-4038-9049-3080d79d2165=/key:LABEL=KEYDEV
2018-09-04 16:54:53 +02:00

184 lines
7.7 KiB
XML

<?xml version="1.0"?>
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SPDX-License-Identifier: LGPL-2.1+
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<refentry id="systemd-cryptsetup-generator" conditional='HAVE_LIBCRYPTSETUP'>
<refentryinfo>
<title>systemd-cryptsetup-generator</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>systemd-cryptsetup-generator</refentrytitle>
<manvolnum>8</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd-cryptsetup-generator</refname>
<refpurpose>Unit generator for <filename>/etc/crypttab</filename></refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename>/usr/lib/systemd/system-generators/systemd-cryptsetup-generator</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><filename>systemd-cryptsetup-generator</filename> is a
generator that translates <filename>/etc/crypttab</filename> into
native systemd units early at boot and when configuration of the
system manager is reloaded. This will create
<citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
units as necessary.</para>
<para><filename>systemd-cryptsetup-generator</filename> implements
<citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
</refsect1>
<refsect1>
<title>Kernel Command Line</title>
<para><filename>systemd-cryptsetup-generator</filename>
understands the following kernel command line parameters:</para>
<variablelist class='kernel-commandline-options'>
<varlistentry>
<term><varname>luks=</varname></term>
<term><varname>rd.luks=</varname></term>
<listitem><para>Takes a boolean argument. Defaults to
<literal>yes</literal>. If <literal>no</literal>, disables the
generator entirely. <varname>rd.luks=</varname> is honored
only by initial RAM disk (initrd) while
<varname>luks=</varname> is honored by both the main system
and the initrd. </para></listitem>
</varlistentry>
<varlistentry>
<term><varname>luks.crypttab=</varname></term>
<term><varname>rd.luks.crypttab=</varname></term>
<listitem><para>Takes a boolean argument. Defaults to
<literal>yes</literal>. If <literal>no</literal>, causes the
generator to ignore any devices configured in
<filename>/etc/crypttab</filename>
(<varname>luks.uuid=</varname> will still work however).
<varname>rd.luks.crypttab=</varname> is honored only by
initial RAM disk (initrd) while
<varname>luks.crypttab=</varname> is honored by both the main
system and the initrd. </para></listitem>
</varlistentry>
<varlistentry>
<term><varname>luks.uuid=</varname></term>
<term><varname>rd.luks.uuid=</varname></term>
<listitem><para>Takes a LUKS superblock UUID as argument. This
will activate the specified device as part of the boot process
as if it was listed in <filename>/etc/crypttab</filename>.
This option may be specified more than once in order to set up
multiple devices. <varname>rd.luks.uuid=</varname> is honored
only by initial RAM disk (initrd) while
<varname>luks.uuid=</varname> is honored by both the main
system and the initrd.</para>
<para>If /etc/crypttab contains entries with the same UUID,
then the name, keyfile and options specified there will be
used. Otherwise, the device will have the name
<literal>luks-UUID</literal>.</para>
<para>If /etc/crypttab exists, only those UUIDs
specified on the kernel command line
will be activated in the initrd or the real root.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>luks.name=</varname></term>
<term><varname>rd.luks.name=</varname></term>
<listitem><para>Takes a LUKS super block UUID followed by an
<literal>=</literal> and a name. This implies
<varname>rd.luks.uuid=</varname> or
<varname>luks.uuid=</varname> and will additionally make the
LUKS device given by the UUID appear under the provided
name.</para>
<para><varname>rd.luks.name=</varname> is honored only by
initial RAM disk (initrd) while <varname>luks.name=</varname>
is honored by both the main system and the initrd.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>luks.options=</varname></term>
<term><varname>rd.luks.options=</varname></term>
<listitem><para>Takes a LUKS super block UUID followed by an
<literal>=</literal> and a string of options separated by
commas as argument. This will override the options for the
given UUID.</para>
<para>If only a list of options, without an UUID, is
specified, they apply to any UUIDs not specified elsewhere,
and without an entry in
<filename>/etc/crypttab</filename>.</para><para>
<varname>rd.luks.options=</varname> is honored only by initial
RAM disk (initrd) while <varname>luks.options=</varname> is
honored by both the main system and the initrd.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>luks.key=</varname></term>
<term><varname>rd.luks.key=</varname></term>
<listitem><para>Takes a password file name as argument or a
LUKS super block UUID followed by a <literal>=</literal> and a
password file name.</para>
<para>For those entries specified with
<varname>rd.luks.uuid=</varname> or
<varname>luks.uuid=</varname>, the password file will be set
to the one specified by <varname>rd.luks.key=</varname> or
<varname>luks.key=</varname> of the corresponding UUID, or the
password file that was specified without a UUID.</para>
<para>It is also possible to specify an external device which
should be mounted before we attempt to unlock the LUKS device.
systemd-cryptsetup will use password file stored on that
device. Device containing password file is specified by
appending colon and a device identifier to the password file
path. For example,
<varname>rd.luks.uuid=</varname>b40f1abf-2a53-400a-889a-2eccc27eaa40
<varname>rd.luks.key=</varname>b40f1abf-2a53-400a-889a-2eccc27eaa40=/keyfile:LABEL=keydev.
Hence, in this case, we will attempt to mount file system
residing on the block device with label <literal>keydev</literal>.
This syntax is for now only supported on a per-device basis,
i.e. you have to specify LUKS device UUID.</para>
<para><varname>rd.luks.key=</varname>
is honored only by initial RAM disk
(initrd) while
<varname>luks.key=</varname> is
honored by both the main system and
the initrd.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>