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