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<?xml version="1.0"?>
<!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<refentry id="systemd-cryptsetup" conditional='HAVE_LIBCRYPTSETUP'>
<refentryinfo>
<title>systemd-cryptsetup</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>systemd-cryptsetup</refentrytitle>
<manvolnum>8</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd-cryptsetup</refname>
<refname>systemd-cryptsetup@.service</refname>
<!-- <refname>system-systemd\x2dcryptsetup.slice</refname> — this causes meson to go haywire because it
thinks this is a (windows) path. Let's just not create the alias for this name, and only include it
in the synopsis. -->
<refpurpose>Full disk decryption logic</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>systemd-cryptsetup</command>
<arg choice="opt" rep="repeat">OPTIONS</arg>
<arg choice="plain">attach</arg>
<arg choice="plain">VOLUME</arg>
<arg choice="plain">SOURCE-DEVICE</arg>
<arg choice="opt">KEY-FILE</arg>
<arg choice="opt">CONFIG</arg>
</cmdsynopsis>
<cmdsynopsis>
<command>systemd-cryptsetup</command>
<arg choice="opt" rep="repeat">OPTIONS</arg>
<arg choice="plain">detach</arg>
<arg choice="plain">VOLUME</arg>
</cmdsynopsis>
<para><filename>systemd-cryptsetup@.service</filename></para>
<para><filename>system-systemd\x2dcryptsetup.slice</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><filename>systemd-cryptsetup</filename> is used to set up (with <command>attach</command>) and tear
down (with <command>detach</command>) access to an encrypted block device. It is primarily used via
<filename>systemd-cryptsetup@.service</filename> during early boot, but may also be be called manually.
The positional arguments <parameter>VOLUME</parameter>, <parameter>SOURCE-DEVICE</parameter>,
<parameter>KEY-FILE</parameter>, and <parameter>CRYPTTAB-OPTIONS</parameter> have the same meaning as the
fields in <citerefentry><refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
</para>
<para><filename>systemd-cryptsetup@.service</filename> is a service responsible for providing access to
encrypted block devices. It is instantiated for each device that requires decryption.</para>
<para><filename>systemd-cryptsetup@.service</filename> instances are part of the
<filename>system-systemd\x2dcryptsetup.slice</filename> slice, which is destroyed only very late in the
shutdown procedure. This allows the encrypted devices to remain up until filesystems have been unmounted.
</para>
<para><filename>systemd-cryptsetup@.service</filename> will ask
for hard disk passwords via the <ulink
url="https://systemd.io/PASSWORD_AGENTS/">password agent logic</ulink>, in
order to query the user for the password using the right mechanism at boot
and during runtime.</para>
<para>At early boot and when the system manager configuration is reloaded, <filename>/etc/crypttab</filename> is
translated into <filename>systemd-cryptsetup@.service</filename> units by
<citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
<para>In order to unlock a volume a password or binary key is required.
<filename>systemd-cryptsetup@.service</filename> tries to acquire a suitable password or binary key via
the following mechanisms, tried in order:</para>
<orderedlist>
<listitem><para>If a key file is explicitly configured (via the third column in
<filename>/etc/crypttab</filename>), a key read from it is used. If a PKCS#11 token, FIDO2 token or
TPM2 device is configured (using the <varname>pkcs11-uri=</varname>, <varname>fido2-device=</varname>,
<varname>tpm2-device=</varname> options) the key is decrypted before use.</para></listitem>
<listitem><para>If no key file is configured explicitly this way, a key file is automatically loaded
from <filename>/etc/cryptsetup-keys.d/<replaceable>volume</replaceable>.key</filename> and
<filename>/run/cryptsetup-keys.d/<replaceable>volume</replaceable>.key</filename>, if present. Here
too, if a PKCS#11/FIDO2/TPM2 token/device is configured, any key found this way is decrypted before
use.</para></listitem>
<listitem><para>If the <varname>try-empty-password</varname> option is specified then unlocking the
volume with an empty password is attempted.</para></listitem>
<listitem><para>The kernel keyring is then checked for a suitable cached password from previous
attempts.</para></listitem>
<listitem><para>Finally, the user is queried for a password, possibly multiple times, unless
the <varname>headless</varname> option is set.</para></listitem>
</orderedlist>
<para>If no suitable key may be acquired via any of the mechanisms describes above, volume activation fails.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-cryptenroll</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<ulink url="https://systemd.io/TPM2_PCR_MEASUREMENTS">TPM2 PCR Measurements Made by systemd</ulink>
</para>
</refsect1>
</refentry>
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