mirror of
https://github.com/systemd/systemd
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342 lines
15 KiB
XML
342 lines
15 KiB
XML
<?xml version='1.0'?> <!--*-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="loader.conf" conditional='HAVE_GNU_EFI'
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>loader.conf</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>loader.conf</refentrytitle>
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<manvolnum>5</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>loader.conf</refname>
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<refpurpose>Configuration file for systemd-boot</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename><replaceable>ESP</replaceable>/loader/loader.conf</filename>,
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<filename><replaceable>ESP</replaceable>/loader/entries/*.conf</filename>
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<filename><replaceable>XBOOTLDR</replaceable>/loader/entries/*.conf</filename>
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</para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>
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<citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry> will
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read <filename><replaceable>ESP</replaceable>/loader/loader.conf</filename>, and any files with the
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<literal>.conf</literal> extension under
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<filename><replaceable>ESP</replaceable>/loader/entries/</filename> on the EFI system partition (ESP),
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and <filename><replaceable>XBOOTLDR</replaceable>/loader/entries/</filename> on the extended boot loader
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partition (XBOOTLDR) as defined by <ulink url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader
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Specification</ulink>.
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</para>
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<para>Each of these configuration files must consist of series of newline (i.e. ASCII code 10) separated
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lines, each consisting of an option name, followed by whitespace, and the option
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value. <literal>#</literal> may be used to start a comment line. Empty and comment lines are ignored. The
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files use UTF-8 encoding.</para>
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<para>Boolean arguments may be written as
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<literal>yes</literal>/<literal>y</literal>/<literal>true</literal>/<literal>t</literal>/<literal>on</literal>/<literal>1</literal> or
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<literal>no</literal>/<literal>n</literal>/<literal>false</literal>/<literal>f</literal>/<literal>off</literal>/<literal>0</literal>.
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</para>
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</refsect1>
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<refsect1>
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<title>Options</title>
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<para>The configuration options supported by
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<filename><replaceable>ESP</replaceable>/loader/entries/*.conf</filename> and
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<filename><replaceable>XBOOTLDR</replaceable>/loader/entries/*.conf</filename> files are defined as part
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of the <ulink url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader
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Specification</ulink>.</para>
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<para>The following configuration are supported by the <filename>loader.conf</filename> configuration
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file:</para>
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<variablelist>
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<varlistentry>
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<term>default</term>
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<listitem><para>A glob pattern to select the default entry. The default entry
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may be changed in the boot menu itself, in which case the name of the
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selected entry will be stored as an EFI variable, overriding this option.
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</para>
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<para>If set to <literal>@saved</literal> the chosen entry will be saved as an EFI variable
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on every boot and automatically selected the next time the boot loader starts.</para>
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<table>
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<title>Automatically detected entries will use the following names:</title>
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<tgroup cols='2'>
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<colspec colname='name' />
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<colspec colname='expl' />
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<thead>
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<row>
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<entry>Name</entry>
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<entry>Description</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>auto-efi-default</entry>
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<entry>EFI Default Loader</entry>
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</row>
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<row>
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<entry>auto-efi-shell</entry>
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<entry>EFI Shell</entry>
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</row>
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<row>
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<entry>auto-osx</entry>
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<entry>macOS</entry>
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</row>
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<row>
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<entry>auto-reboot-to-firmware-setup</entry>
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<entry>Reboot Into Firmware Interface</entry>
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</row>
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<row>
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<entry>auto-windows</entry>
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<entry>Windows Boot Manager</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>Supported glob wildcard patterns are <literal>?</literal>, <literal>*</literal>, and
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<literal>[…]</literal> (including ranges). Note that these patterns use the same syntax as
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<citerefentry project='man-pages'><refentrytitle>glob</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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but do not support all features. In particular, set negation and named character classes are not
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supported. The matching is done case-insensitively on the entry ID (as shown by <command>bootctl
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list</command>).</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>timeout</term>
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<listitem><para>How long the boot menu should be shown before the default
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entry is booted, in seconds. This may be changed in the boot menu itself and
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will be stored as an EFI variable in that case, overriding this option.
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</para>
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<para>If set to <literal>menu-hidden</literal> or <literal>0</literal> (the default) no menu
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is shown and the default entry will be booted immediately. The menu can be shown
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by pressing and holding a key before systemd-boot is launched. Setting this to
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<literal>menu-force</literal> disables the timeout while always showing the menu.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>console-mode</term>
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<listitem><para>This option configures the resolution of the console. Takes a
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number or one of the special values listed below. The following values may be
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used:</para>
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<variablelist>
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<varlistentry>
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<term>0</term>
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<listitem>
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<para>Standard UEFI 80x25 mode</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>1</term>
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<listitem>
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<para>80x50 mode, not supported by all devices</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>2</term>
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<listitem>
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<para>the first non-standard mode provided by the device
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firmware, if any</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>auto</term>
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<listitem>
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<para>Pick a suitable mode automatically using heuristics</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>max</term>
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<listitem>
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<para>Pick the highest-numbered available mode</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>keep</term>
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<listitem>
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<para>Keep the mode selected by firmware (the default)</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>editor</term>
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<listitem><para>Takes a boolean argument. Enable (the default) or disable the
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editor. The editor should be disabled if the machine can be accessed by
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unauthorized persons.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>auto-entries</term>
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<listitem><para>Takes a boolean argument. Enable (the default) or disable
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entries for other boot entries found on the boot partition. In particular,
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this may be useful when loader entries are created to show replacement
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descriptions for those entries.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>auto-firmware</term>
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<listitem><para>A boolean controlling the presence of the "Reboot into firmware" entry
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(enabled by default). If this is disabled, the firmware interface may still be reached
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by using the <keycap>f</keycap> key.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>beep</term>
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<listitem><para>Takes a boolean argument. If timeout enabled beep every second, otherwise beep n times when n-th entry in boot menu is selected (default disabled).
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Currently, only x86 is supported, where it uses the PC speaker.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>secure-boot-enroll</term>
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<listitem><para>Danger: this feature might soft-brick your device if used improperly.</para>
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<para>Takes one of <literal>off</literal>, <literal>manual</literal> or <literal>force</literal>.
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Controls the enrollment of secure boot keys. If set to <literal>off</literal>, no action whatsoever
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is taken. If set to <literal>manual</literal> (the default) and the UEFI firmware is in setup-mode
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then entries to manually enroll Secure Boot variables are created in the boot menu. If set to
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<literal>force</literal>, in addition, if a directory named <filename>/loader/keys/auto/</filename>
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exists on the ESP then the keys in that directory are enrolled automatically.</para>
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<para>The different sets of variables can be set up under <filename>/loader/keys/<replaceable>NAME</replaceable></filename>
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where <replaceable>NAME</replaceable> is the name that is going to be used as the name of the entry.
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This allows to ship multiple sets of Secure Boot variables and choose which one to enroll at runtime.</para>
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<para>Supported secure boot variables are one database for authorized images, one key exchange key (KEK)
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and one platform key (PK). For more information, refer to the <ulink url="https://uefi.org/specifications">UEFI specification</ulink>,
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under Secure Boot and Driver Signing. Another resource that describe the interplay of the different variables is the
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<ulink url="https://edk2-docs.gitbook.io/understanding-the-uefi-secure-boot-chain/secure_boot_chain_in_uefi/uefi_secure_boot">
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EDK2 documentation</ulink>.</para>
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<para>A complete set of UEFI variable includes <filename>db.esl</filename>, <filename>KEK.esl</filename>
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and <filename>PK.esl</filename>. Note that these files need to be authenticated UEFI variables. See
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below for an example of how to generate them from regular X.509 keys.</para>
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<programlisting>uuid=$(systemd-id128 new --uuid)
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for key in PK KEK db; do
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openssl req -new -x509 -subj "/CN=${key}/" -keyout "${key}.key" -out "${key}.crt"
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openssl x509 -outform DER -in "${key}.crt" -out "${key}.cer"
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cert-to-efi-sig-list -g "${uuid}" "${key}.crt" "${key}.tmp"
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done
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sign-efi-sig-list -c PK.crt -k PK.key PK PK.tmp PK.esl
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sign-efi-sig-list -c PK.crt -k PK.key KEK KEK.tmp KEK.esl
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sign-efi-sig-list -c KEK.crt -k KEK.key db db.tmp db.esl
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</programlisting>
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<para>This feature is considered dangerous because even if all the required files are signed with the
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keys being loaded, some files necessary for the system to function properly still won't be. This
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is especially the case with Option ROMs (e.g. for storage controllers or graphics cards). See
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<ulink url="https://github.com/Foxboron/sbctl/wiki/FAQ#option-rom">Secure Boot and Option ROMs</ulink>
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for more details.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>reboot-for-bitlocker</term>
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<listitem><para>Caveat: This feature is experimental, and is likely to be changed (or removed in its
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current form) in a future version of systemd.</para>
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<para>Work around BitLocker requiring a recovery key when the boot loader was
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updated (disabled by default).</para>
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<para>Try to detect BitLocker encrypted drives along with an active TPM. If both are found
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and Windows Boot Manager is selected in the boot menu, set the <literal>BootNext</literal>
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EFI variable and restart the system. The firmware will then start Windows Boot Manager
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directly, leaving the TPM PCRs in expected states so that Windows can unseal the encryption
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key. This allows systemd-boot to be updated without having to provide the recovery key for
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BitLocker drive unlocking.</para>
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<para>Note that the PCRs that Windows uses can be configured with the
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<literal>Configure TPM platform validation profile for native UEFI firmware configurations</literal>
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group policy under <literal>Computer Configuration\Administrative Templates\Windows Components\BitLocker Drive Encryption</literal>.
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When secure boot is enabled, changing this to PCRs <literal>0,2,7,11</literal> should be safe.
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The TPM key protector needs to be removed and then added back for the PCRs on an already
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encrypted drive to change. If PCR 4 is not measured, this setting can be disabled to speed
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up booting into Windows.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>random-seed-mode</term>
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<listitem><para>Takes one of <literal>off</literal>, <literal>with-system-token</literal> and
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<literal>always</literal>. If <literal>off</literal> no random seed data is read off the ESP, nor
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passed to the OS. If <literal>with-system-token</literal> (the default)
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<command>systemd-boot</command> will read a random seed from the ESP (from the file
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<filename>/loader/random-seed</filename>) only if the <varname>LoaderSystemToken</varname> EFI
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variable is set, and then derive the random seed to pass to the OS from the combination. If
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<literal>always</literal> the boot loader will do so even if <varname>LoaderSystemToken</varname> is
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not set. This mode is useful in environments where protection against OS image reuse is not a
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concern, and the random seed shall be used even with no further setup in place. Use <command>bootctl
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random-seed</command> to initialize both the random seed file in the ESP and the system token EFI
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variable.</para>
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<para>See <ulink url="https://systemd.io/RANDOM_SEEDS">Random Seeds</ulink> for further
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information.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Example</title>
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<programlisting># /boot/efi/loader/loader.conf
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timeout 0
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default 01234567890abcdef1234567890abdf0-*
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editor no
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</programlisting>
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<para>The menu will not be shown by default (the menu can still be shown by
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pressing and holding a key during boot). One of the entries with files with a
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name starting with <literal>01234567890abcdef1234567890abdf0-</literal> will be
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selected by default. If more than one entry matches, the one with the highest
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priority will be selected (generally the one with the highest version number).
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The editor will be disabled, so it is not possible to alter the kernel command
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line.</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-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>bootctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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