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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"
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 initramfs images to and from /boot</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>kernel-install</command>
<arg choice="plain">COMMAND</arg>
<arg choice="opt" rep="repeat">OPTIONS</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 initramfs images 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 execute the files
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 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. <command>kernel-install</command> calls the executables from
<filename>/usr/lib/kernel/install.d/*.install</filename> and
<filename>/etc/kernel/install.d/*.install</filename> with the following arguments:
<programlisting>add <replaceable>KERNEL-VERSION</replaceable> <filename>$BOOT/<replaceable>MACHINE-ID</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/</filename> <replaceable>KERNEL-IMAGE</replaceable> [<replaceable>INITRD-FILE</replaceable> ...]</programlisting>
</para>
<para>Three default plugins execute the following operations in this case:</para>
<itemizedlist>
<listitem><para><filename>00-entry-directory.install</filename> creates the directory
<filename>$BOOT/<replaceable>MACHINE-ID</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/</filename>
if <filename>$BOOT/<replaceable>MACHINE-ID</replaceable>/</filename> already exists.
</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>$BOOT/<replaceable>MACHINE-ID</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/linux</filename>.
If an <replaceable>INITRD-FILE</replaceable> is provided, it also copies <replaceable>INITRD-FILE</replaceable>
to
<filename>$BOOT/<replaceable>MACHINE-ID</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> in
<filename>$BOOT/loader/entries/<replaceable>MACHINE-ID</replaceable>-<replaceable>KERNEL-VERSION</replaceable>.conf</filename>.
The title of the entry is the <replaceable>PRETTY_NAME</replaceable> parameter specified in
<filename>/etc/os-release</filename> or <filename>/usr/lib/os-release</filename> (if the former is
missing), or "Linux <replaceable>KERNEL-VERSION</replaceable>", if unset.</para>
<para>If the entry directory
<filename>$BOOT/<replaceable>MACHINE-ID</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/</filename>
does not exist, 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:
<programlisting>remove <replaceable>KERNEL-VERSION</replaceable> <filename>$BOOT/<replaceable>MACHINE-ID</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/</filename></programlisting>
</para>
<para>Afterwards, <command>kernel-install</command> removes the directory
<filename>$BOOT/<replaceable>MACHINE-ID</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/</filename>
and its contents.</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>$BOOT/loader/entries/<replaceable>MACHINE-ID</replaceable>-<replaceable>KERNEL-VERSION</replaceable>.conf</filename>.</para></listitem>
</itemizedlist>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>The <varname>$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>$BOOT/$MACHINE_ID/</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" />
</variablelist>
</refsect1>
<refsect1>
<title>Environment variables</title>
<para>If <option>--verbose</option> is used, <varname>$KERNEL_INSTALL_VERBOSE=1</varname> will be set for
the plugins. They may output additional logs in this case.</para>
</refsect1>
<refsect1>
<title>Exit status</title>
<para>If every executable returns 0 or 77, 0 is returned, and a non-zero failure code otherwise.</para>
</refsect1>
<refsect1>
<title>Files</title>
<variablelist>
<varlistentry>
<term>
<filename>/usr/lib/kernel/install.d/*.install</filename>
<filename>/etc/kernel/install.d/*.install</filename>
</term>
<listitem>
<para>Drop-in files which are executed by kernel-install.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<filename>/etc/kernel/cmdline</filename>
<filename>/proc/cmdline</filename>
</term>
<listitem>
<para>Read by <filename>90-loaderentry.install</filename>. The content of the file
<filename>/etc/kernel/cmdline</filename> specifies the kernel command line to use. If that file does not
exist, <filename>/proc/cmdline</filename> is used.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<filename>/etc/kernel/tries</filename>
</term>
<listitem>
<para>Read by <filename>90-loaderentry.install</filename>. If this file exists a numeric value is read from
it and the naming of the generated entry file is slightly altered to include it as
<filename>$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.</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>. If it cannot read <filename>/etc/machine-id</filename>,
kernel-install will use "Linux" as the machine ID instead.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<filename>/etc/os-release</filename>
<filename>/usr/lib/os-release</filename>
</term>
<listitem>
<para>The content of the file specifies the operating system title <replaceable>PRETTY_NAME</replaceable>.</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>
|
