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+<?xml version='1.0'?>
+<!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="kernel-install" conditional='ENABLE_KERNEL_INSTALL'
+ xmlns:xi="http://www.w3.org/2001/XInclude">
+
+ <refentryinfo>
+ <title>kernel-install</title>
+ <productname>systemd</productname>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>kernel-install</refentrytitle>
+ <manvolnum>8</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>kernel-install</refname>
+ <refpurpose>Add and remove kernel and initrd images to and from /boot</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <cmdsynopsis>
+ <command>kernel-install</command>
+ <arg choice="opt" rep="repeat">OPTIONS</arg>
+ <arg choice="plain">COMMAND</arg>
+ <arg choice="plain"><replaceable>KERNEL-VERSION</replaceable></arg>
+ <arg choice="plain"><replaceable>KERNEL-IMAGE</replaceable></arg>
+ <arg choice="opt" rep="repeat"><replaceable>INITRD-FILE</replaceable></arg>
+ </cmdsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+ <para><command>kernel-install</command> is used to install and remove kernel and initrd images
+ <footnote>
+ <para>Nowadays actually CPIO archives used as an "initramfs", rather than "initrd". See
+ <citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry> for an
+ explanation.</para>
+ </footnote>
+ to and from the boot loader partition, referred to as <varname>$BOOT</varname> here. It will usually be
+ one of <filename>/boot/</filename>, <filename>/efi/</filename>, or <filename>/boot/efi/</filename>, see
+ below.</para>
+
+ <para><command>kernel-install</command> will run the executable files ("plugins") located in the
+ directory <filename>/usr/lib/kernel/install.d/</filename> and the local administration directory
+ <filename>/etc/kernel/install.d/</filename>. All files are collectively sorted and executed in lexical
+ order, regardless of the directory in which they live. However, files with identical filenames replace
+ each other. Files in <filename>/etc/kernel/install.d/</filename> take precedence over files with the
+ same name in <filename>/usr/lib/kernel/install.d/</filename>. This can be used to override a
+ system-supplied executables with a local file if needed; a symbolic link in
+ <filename>/etc/kernel/install.d/</filename> with the same name as an executable in
+ <filename>/usr/lib/kernel/install.d/</filename>, pointing to <filename>/dev/null</filename>, disables the
+ executable entirely. Executables must have the extension <literal>.install</literal>; other extensions
+ are ignored.</para>
+
+ <para>An executable placed in these directories should return <constant>0</constant> on success. It may
+ also return <constant>77</constant> to cause the whole operation to terminate (executables later in
+ lexical order will be skipped).</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Commands</title>
+ <para>The following commands are understood:</para>
+ <variablelist>
+ <varlistentry>
+ <term><command>add <replaceable>KERNEL-VERSION</replaceable> <replaceable>KERNEL-IMAGE</replaceable> [<replaceable>INITRD-FILE</replaceable> ...]</command></term>
+ <listitem>
+ <para>This command expects a kernel version string and a path to a kernel image file as arguments.
+ Optionally, one or more initrd images may be specified as well (note that plugins might generate
+ additional ones). <command>kernel-install</command> calls the executable files from
+ <filename>/usr/lib/kernel/install.d/*.install</filename> and
+ <filename>/etc/kernel/install.d/*.install</filename> (i.e. the plugins) with the following
+ arguments:</para>
+
+ <programlisting>add <replaceable>KERNEL-VERSION</replaceable> <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/</filename> <replaceable>KERNEL-IMAGE</replaceable> [<replaceable>INITRD-FILE</replaceable> ...]</programlisting>
+
+ <para>The third argument directly refers to the path where to place kernel images, initrd
+ images and other resources for <ulink url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot
+ Loader Specification</ulink> Type #1 entries (the "entry directory"). If other boot loader schemes
+ are used the parameter may be ignored. The <replaceable>ENTRY-TOKEN</replaceable> string is
+ typically the machine ID and is supposed to identify the local installation on the system. For
+ details see below.</para>
+
+ <para>Two default plugins execute the following operations in this case:</para>
+
+ <itemizedlist>
+ <listitem><para><command>kernel-install</command> creates
+ <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable>/<replaceable>KERNEL-VERSION</replaceable></filename>,
+ if enabled (see <varname>$KERNEL_INSTALL_LAYOUT</varname>).</para></listitem>
+
+ <listitem><para><filename>50-depmod.install</filename> runs
+ <citerefentry project='man-pages'><refentrytitle>depmod</refentrytitle><manvolnum>8</manvolnum></citerefentry> for the
+ <replaceable>KERNEL-VERSION</replaceable>.</para></listitem>
+
+ <listitem><para><filename>90-loaderentry.install</filename> copies
+ <replaceable>KERNEL-IMAGE</replaceable> to
+ <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/linux</filename>.
+ If <replaceable>INITRD-FILE</replaceable>s are provided, it also copies them to
+ <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable>/<replaceable>KERNEL_VERSION</replaceable>/<replaceable>INITRD-FILE</replaceable></filename>.
+ It also creates a boot loader entry according to the <ulink
+ url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader Specification</ulink> (Type #1) in
+ <filename>$BOOT/loader/entries/<replaceable>ENTRY-TOKEN</replaceable>-<replaceable>KERNEL-VERSION</replaceable>.conf</filename>.
+ The title of the entry is the <replaceable>PRETTY_NAME</replaceable> parameter specified in
+ <filename>/etc/os-release</filename> or <filename>/usr/lib/os-release</filename> (if the former
+ is missing), or "Linux <replaceable>KERNEL-VERSION</replaceable>", if unset.</para>
+
+ <para>If <varname>$KERNEL_INSTALL_LAYOUT</varname> is not "bls", this plugin does nothing.</para></listitem>
+ </itemizedlist>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><command>remove <replaceable>KERNEL-VERSION</replaceable></command></term>
+ <listitem>
+ <para>This command expects a kernel version string as single argument. This calls executables from
+ <filename>/usr/lib/kernel/install.d/*.install</filename> and
+ <filename>/etc/kernel/install.d/*.install</filename> with the following arguments:
+ </para>
+
+ <programlisting>remove <replaceable>KERNEL-VERSION</replaceable> <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/</filename></programlisting>
+
+ <para>Afterwards, <command>kernel-install</command> removes the entry directory
+ <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/</filename>
+ and its contents, if it exists.</para>
+
+ <para>Two default plugins execute the following operations in this case:</para>
+
+ <itemizedlist>
+ <listitem><para><filename>50-depmod.install</filename> removes the files generated by <command>depmod</command> for this kernel again.</para></listitem>
+
+ <listitem><para><filename>90-loaderentry.install</filename> removes the file
+ <filename>$BOOT/loader/entries/<replaceable>ENTRY-TOKEN</replaceable>-<replaceable>KERNEL-VERSION</replaceable>.conf</filename>.</para></listitem>
+ </itemizedlist>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><command>inspect</command></term>
+ <listitem>
+ <para>Shows the various paths and parameters configured or auto-detected. In particular shows the
+ values of the various <varname>$KERNEL_INSTALL_*</varname> environment variables listed
+ below.</para>
+ </listitem>
+ </varlistentry>
+
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>The <varname>$BOOT</varname> partition</title>
+
+ <para>The partition where the kernels and <ulink url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot
+ Loader Specification</ulink> snippets are located is called <varname>$BOOT</varname>.
+ <command>kernel-install</command> determines the location of this partition by checking
+ <filename>/efi/</filename>, <filename>/boot/</filename>, and <filename>/boot/efi/</filename> in turn. The
+ first location where <filename>$BOOT/loader/entries/</filename> or
+ <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable>/</filename> exists is used.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Options</title>
+ <para>The following options are understood:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><option>-v</option></term>
+ <term><option>--verbose</option></term>
+ <listitem>
+ <para>Output additional information about operations being performed.</para>
+ </listitem>
+ </varlistentry>
+
+ <xi:include href="standard-options.xml" xpointer="help" />
+ <xi:include href="standard-options.xml" xpointer="version" />
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Environment variables</title>
+
+ <refsect2>
+ <title>Environment variables exported for plugins</title>
+
+ <para>If <option>--verbose</option> is used, <varname>$KERNEL_INSTALL_VERBOSE=1</varname> will be
+ exported for plugins. They may output additional logs in this case.</para>
+
+ <para><varname>$KERNEL_INSTALL_MACHINE_ID</varname> is set for the plugins to the desired machine-id to
+ use. It's always a 128-bit ID. Normally it's read from <filename>/etc/machine-id</filename>, but it can
+ also be overridden via <varname>$MACHINE_ID</varname> (see below). If not specified via these methods a
+ fallback value will generated by <command>kernel-install</command>, and used only for a single
+ invocation.</para>
+
+ <para><varname>$KERNEL_INSTALL_ENTRY_TOKEN</varname> is set for the plugins to the desired entry
+ "token" to use. It's an identifier that shall be used to identify the local installation, and is often
+ the machine ID, i.e. same as <varname>$KERNEL_INSTALL_MACHINE_ID</varname>, but might also be a
+ different type of identifier, for example a fixed string or the <varname>ID=</varname>,
+ <varname>IMAGE_ID=</varname> values from <filename>/etc/os-release</filename>. The string passed here
+ will be used to name Boot Loader Specification entries, or the directories the kernel image and initial
+ RAM disk images are placed into.</para>
+
+ <para>Note that while <varname>$KERNEL_INSTALL_ENTRY_TOKEN</varname> and
+ <varname>$KERNEL_INSTALL_MACHINE_ID</varname> are often set to the same value, the latter is guaranteed
+ to be a valid 32 character ID in lowercase hexadecimals while the former can be any short string. The
+ entry token to use is read from <filename>/etc/kernel/entry-token</filename>, if it exists. Otherwise a
+ few possible candidates below <varname>$BOOT</varname> are checked for Boot Loader Specification Type 1
+ entry directories, and if found the entry token is derived from that. If that is not successful,
+ <varname>$KERNEL_INSTALL_MACHINE_ID</varname> is used as fallback.</para>
+
+ <para><varname>$KERNEL_INSTALL_BOOT_ROOT</varname> is set for the plugins to the absolute path of the
+ root directory (mount point, usually) of the hierarchy where boot loader entries, kernel images, and
+ associated resources should be placed. This usually is the path where the XBOOTLDR partition or the ESP
+ (EFI System Partition) are mounted, and also conceptually referred to as <varname>$BOOT</varname>. Can
+ be overridden by setting <varname>$BOOT_ROOT</varname> (see below).</para>
+
+ <para><varname>$KERNEL_INSTALL_LAYOUT=bls|other|...</varname> is set for the plugins to specify the
+ installation layout. Defaults to <option>bls</option> if
+ <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable></filename> exists, or <option>other</option>
+ otherwise. Additional layout names may be defined by convention. If a plugin uses a special layout,
+ it's encouraged to declare its own layout name and configure <varname>layout=</varname> in
+ <filename>install.conf</filename> upon initial installation. The following values are currently
+ understood:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term>bls</term>
+ <listitem>
+ <para>Standard <ulink url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader
+ Specification</ulink> Type #1 layout, compatible with
+ <citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry>:
+ entries in
+ <filename>$BOOT/loader/entries/<replaceable>ENTRY-TOKEN</replaceable>-<replaceable>KERNEL-VERSION</replaceable>[+<replaceable>TRIES</replaceable>].conf</filename>,
+ kernel and initrds under
+ <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/</filename></para>
+ <para>Implemented by <filename>90-loaderentry.install</filename>.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>other</term>
+ <listitem>
+ <para>Some other layout not understood natively by <command>kernel-install</command>.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <para><varname>$KERNEL_INSTALL_INITRD_GENERATOR</varname> is set for plugins to select the initrd
+ generator. This may be configured as <varname>initrd_generator=</varname> in
+ <filename>install.conf</filename>, see below.</para>
+
+ <para><varname>$KERNEL_INSTALL_STAGING_AREA</varname> is set for plugins to a path to a directory.
+ Plugins may drop files in that directory, and they will be installed as part of the loader entry, based
+ on the file name and extension.</para>
+ </refsect2>
+
+ <refsect2>
+ <title>Environment variables understood by <command>kernel-install</command></title>
+
+ <para><varname>$KERNEL_INSTALL_CONF_ROOT</varname> can be set to override the location of the
+ configuration files read by <command>kernel-install</command>. When set,
+ <filename>install.conf</filename>, <filename>entry-token</filename>, and other files will be
+ read from this directory.</para>
+
+ <para><varname>$KERNEL_INSTALL_PLUGINS</varname> can be set to override the list of plugins executed by
+ <command>kernel-install</command>. The argument is a whitespace-separated list of paths.
+ <literal>KERNEL_INSTALL_PLUGINS=:</literal> may be used to prevent any plugins from running.
+ </para>
+
+ <para><varname>$MACHINE_ID</varname> can be set for <command>kernel-install</command> to override
+ <varname>$KERNEL_INSTALL_MACHINE_ID</varname>, the machine ID.</para>
+
+ <para><varname>$BOOT_ROOT</varname> can be set for <command>kernel-install</command> to override
+ <varname>$KERNEL_INSTALL_BOOT_ROOT</varname>, the installation location for boot entries.</para>
+
+ <para>The last two variables may also be set in <filename>install.conf</filename>. Variables set in the
+ environment take precedence over the values specified in the config file.</para>
+ </refsect2>
+ </refsect1>
+
+ <refsect1>
+ <title>Exit status</title>
+ <para>If every executable returns 0 or 77, 0 is returned, and a non-zero failure code otherwise.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Files</title>
+ <variablelist>
+ <varlistentry>
+ <term>
+ <filename>/usr/lib/kernel/install.d/*.install</filename>
+ <filename>/etc/kernel/install.d/*.install</filename>
+ </term>
+ <listitem>
+ <para>Drop-in files which are executed by kernel-install.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>
+ <filename>/usr/lib/kernel/cmdline</filename>
+ <filename>/etc/kernel/cmdline</filename>
+ <filename>/proc/cmdline</filename>
+ </term>
+ <listitem>
+ <para>Read by <filename>90-loaderentry.install</filename>. The content of the file
+ <filename>/etc/kernel/cmdline</filename> specifies the kernel command line to use. If that file
+ does not exist, <filename>/usr/lib/kernel/cmdline</filename> is used. If that also does not
+ exist, <filename>/proc/cmdline</filename> is used. <varname>$KERNEL_INSTALL_CONF_ROOT</varname>
+ may be used to override the path.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>
+ <filename>/etc/kernel/tries</filename>
+ </term>
+ <listitem>
+ <para>Read by <filename>90-loaderentry.install</filename>. If this file exists a numeric value is read from
+ it and the naming of the generated entry file is slightly altered to include it as
+ <filename>$BOOT/loader/entries/<replaceable>MACHINE-ID</replaceable>-<replaceable>KERNEL-VERSION</replaceable>+<replaceable>TRIES</replaceable>.conf</filename>. This
+ is useful for boot loaders such as
+ <citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry> which
+ implement boot attempt counting with a counter embedded in the entry file name.
+ <varname>$KERNEL_INSTALL_CONF_ROOT</varname> may be used to override the path.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>
+ <filename>/etc/kernel/entry-token</filename>
+ </term>
+ <listitem>
+ <para>If this file exists it is read and used as "entry token" for this system, i.e. is used for
+ naming Boot Loader Specification entries, see <varname>$KERNEL_INSTALL_ENTRY_TOKEN</varname>
+ above for details. <varname>$KERNEL_INSTALL_CONF_ROOT</varname> may be used to override the
+ path.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>
+ <filename>/etc/machine-id</filename>
+ </term>
+ <listitem>
+ <para>The content of this file specifies the machine identification
+ <replaceable>MACHINE-ID</replaceable>.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>
+ <filename>/etc/os-release</filename>
+ <filename>/usr/lib/os-release</filename>
+ </term>
+ <listitem>
+ <para>Read by <filename>90-loaderentry.install</filename>.
+ If available, <varname>PRETTY_NAME=</varname> is read from these files and used as the title of the boot menu entry.
+ Otherwise, <literal>Linux <replaceable>KERNEL-VERSION</replaceable></literal> will be used.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>
+ <filename>/usr/lib/kernel/install.conf</filename>
+ <filename>/etc/kernel/install.conf</filename>
+ </term>
+ <listitem>
+ <para>Configuration options for <command>kernel-install</command>, as a series of
+ <varname>KEY=</varname><replaceable>VALUE</replaceable> assignments, compatible with shell
+ syntax, following the same rules as described in
+ <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ <filename>/etc/kernel/install.conf</filename> will be read if present, and
+ <filename>/usr/lib/kernel/install.conf</filename> otherwise. This file is optional.
+ <varname>$KERNEL_INSTALL_CONF_ROOT</varname> may be used to override the path.
+ </para>
+
+ <para>Currently, the following keys are supported:
+ <varname>MACHINE_ID=</varname>,
+ <varname>BOOT_ROOT=</varname>,
+ <varname>layout=</varname>,
+ <varname>initrd_generator=</varname>.
+ See the Environment variables section above for details.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+ <para>
+ <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>depmod</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+ <ulink url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader Specification</ulink>
+ </para>
+ </refsect1>
+
+</refentry>