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367165a406
The general approach of kernel-install was that each plugin would drop in some files into the entry directory. But this doesn't scale well, because if we have multiple initrd generators, or multiple initrds, each generator would need to recreate the logic to put the generated files in the right place. Also, effective cleanup is impossible if anything goes wrong on the way, so we could end up with unused files in $BOOT. So let's invert the process: plugins drop files into $KERNEL_INSTALL_STAGING_AREA, and at the end 90-loaderentry.install DTRT with those files. This allow new plugins like 50-mkosi-initrd.install to be significantly simpler.
311 lines
16 KiB
XML
311 lines
16 KiB
XML
<?xml version='1.0'?>
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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="kernel-install"
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>kernel-install</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>kernel-install</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>kernel-install</refname>
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<refpurpose>Add and remove kernel and initramfs images to and from /boot</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<cmdsynopsis>
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<command>kernel-install</command>
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<arg choice="plain">COMMAND</arg>
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<arg choice="opt" rep="repeat">OPTIONS</arg>
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<arg choice="plain"><replaceable>KERNEL-VERSION</replaceable></arg>
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<arg choice="plain"><replaceable>KERNEL-IMAGE</replaceable></arg>
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<arg choice="opt" rep="repeat"><replaceable>INITRD-FILE</replaceable></arg>
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</cmdsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><command>kernel-install</command> is used to install and remove kernel and initramfs images to and
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from the boot loader partition, referred to as <varname>$BOOT</varname> here. It will usually be one of
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<filename>/boot/</filename>, <filename>/efi/</filename>, or <filename>/boot/efi/</filename>, see below.
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</para>
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<para><command>kernel-install</command> will execute the files
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located in the directory <filename>/usr/lib/kernel/install.d/</filename>
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and the local administration directory <filename>/etc/kernel/install.d/</filename>.
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All files are collectively sorted and executed in lexical order, regardless of the directory in
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which they live. However, files with identical filenames replace each other.
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Files in <filename>/etc/kernel/install.d/</filename> take precedence over files with the same name
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in <filename>/usr/lib/kernel/install.d/</filename>. This can be used to override a system-supplied
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executables with a local file if needed; a symbolic link in <filename>/etc/kernel/install.d/</filename>
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with the same name as an executable in <filename>/usr/lib/kernel/install.d/</filename>,
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pointing to <filename>/dev/null</filename>, disables the executable entirely. Executables must have the
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extension <literal>.install</literal>; other extensions are ignored.</para>
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<para>An executable should return <constant>0</constant> on success. It may also
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return <constant>77</constant> to cause the whole operation to terminate
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(executables later in lexical order will be skipped).</para>
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</refsect1>
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<refsect1>
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<title>Commands</title>
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<para>The following commands are understood:</para>
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<variablelist>
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<varlistentry>
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<term><command>add <replaceable>KERNEL-VERSION</replaceable> <replaceable>KERNEL-IMAGE</replaceable> [<replaceable>INITRD-FILE</replaceable> ...]</command></term>
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<listitem>
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<para>This command expects a kernel version string and a path to a kernel image file as
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arguments. <command>kernel-install</command> calls the executables from
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<filename>/usr/lib/kernel/install.d/*.install</filename> and
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<filename>/etc/kernel/install.d/*.install</filename> with the following arguments:
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<programlisting>add <replaceable>KERNEL-VERSION</replaceable> <filename>$BOOT/<replaceable>MACHINE-ID</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/</filename> <replaceable>KERNEL-IMAGE</replaceable> [<replaceable>INITRD-FILE</replaceable> ...]</programlisting>
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</para>
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<para>Two default plugins execute the following operations in this case:</para>
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<itemizedlist>
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<listitem><para><command>kernel-install</command> creates
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<filename>$BOOT/<replaceable>MACHINE-ID</replaceable>/<replaceable>KERNEL-VERSION</replaceable></filename>,
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if enabled (see <varname>$KERNEL_INSTALL_LAYOUT=</varname>).</para></listitem>
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<listitem><para><filename>50-depmod.install</filename> runs
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<citerefentry project='man-pages'><refentrytitle>depmod</refentrytitle><manvolnum>8</manvolnum></citerefentry> for the
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<replaceable>KERNEL-VERSION</replaceable>.</para></listitem>
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<listitem><para><filename>90-loaderentry.install</filename>
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copies <replaceable>KERNEL-IMAGE</replaceable> to
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<filename>$BOOT/<replaceable>MACHINE-ID</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/linux</filename>.
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If <replaceable>INITRD-FILE</replaceable>s are provided, it also copies them to
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<filename>$BOOT/<replaceable>MACHINE-ID</replaceable>/<replaceable>KERNEL_VERSION</replaceable>/<replaceable>INITRD-FILE</replaceable></filename>.
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It also creates a boot loader entry according to the <ulink
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url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader Specification</ulink> in
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<filename>$BOOT/loader/entries/<replaceable>MACHINE-ID</replaceable>-<replaceable>KERNEL-VERSION</replaceable>.conf</filename>.
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The title of the entry is the <replaceable>PRETTY_NAME</replaceable> parameter specified in
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<filename>/etc/os-release</filename> or <filename>/usr/lib/os-release</filename> (if the former is
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missing), or "Linux <replaceable>KERNEL-VERSION</replaceable>", if unset.</para>
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<para>If <varname>$KERNEL_INSTALL_LAYOUT=</varname> is not "bls", this plugin does nothing.</para></listitem>
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</itemizedlist>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><command>remove <replaceable>KERNEL-VERSION</replaceable></command></term>
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<listitem>
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<para>This command expects a kernel version string as single argument. This calls executables from
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<filename>/usr/lib/kernel/install.d/*.install</filename> and
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<filename>/etc/kernel/install.d/*.install</filename> with the following arguments:
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<programlisting>remove <replaceable>KERNEL-VERSION</replaceable> <filename>$BOOT/<replaceable>MACHINE-ID</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/</filename></programlisting>
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</para>
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<para>Afterwards, <command>kernel-install</command> removes the directory
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<filename>$BOOT/<replaceable>MACHINE-ID</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/</filename>
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and its contents.</para>
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<para>Two default plugins execute the following operations in this case:</para>
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<itemizedlist>
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<listitem><para><filename>50-depmod.install</filename> removes the files generated by <command>depmod</command> for this kernel again.</para></listitem>
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<listitem><para><filename>90-loaderentry.install</filename> removes the file
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<filename>$BOOT/loader/entries/<replaceable>MACHINE-ID</replaceable>-<replaceable>KERNEL-VERSION</replaceable>.conf</filename>.</para></listitem>
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<listitem><para><command>kernel-install</command> removes
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<filename>$BOOT/<replaceable>MACHINE-ID</replaceable>/<replaceable>KERNEL-VERSION</replaceable></filename>,
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if enabled (see <varname>$KERNEL_INSTALL_LAYOUT=</varname>).</para></listitem>
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</itemizedlist>
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</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>The <varname>$BOOT</varname> partition</title>
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<para>The partition where the kernels and <ulink url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot
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Loader Specification</ulink> snippets are located is called <varname>$BOOT</varname>.
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<command>kernel-install</command> determines the location of this partition by checking
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<filename>/efi/</filename>, <filename>/boot/</filename>, and <filename>/boot/efi/</filename>
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in turn. The first location where <filename>$BOOT/loader/entries/</filename> or
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<filename>$BOOT/$MACHINE_ID/</filename> exists is used.</para>
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</refsect1>
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<refsect1>
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<title>Options</title>
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<para>The following options are understood:</para>
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<variablelist>
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<varlistentry>
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<term><option>-v</option></term>
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<term><option>--verbose</option></term>
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<listitem>
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<para>Output additional information about operations being performed.</para>
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</listitem>
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</varlistentry>
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<xi:include href="standard-options.xml" xpointer="help" />
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Environment variables</title>
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<para>If <option>--verbose</option> is used, <varname>$KERNEL_INSTALL_VERBOSE=1</varname> will be set for
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the plugins. They may output additional logs in this case.</para>
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<para>If <varname>MACHINE_ID=</varname> is set and not empty, it will be used as <replaceable>MACHINE-ID</replaceable>,
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overriding any automatic detection attempts. The value must be a valid machine ID (32 hexadecimal characters).</para>
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<para><varname>KERNEL_INSTALL_MACHINE_ID=</varname> is set for the plugins to the desired <replaceable>MACHINE-ID</replaceable> –
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either 32 hexadecimal characters or the special value <literal>Default</literal>.</para>
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<para><varname>KERNEL_INSTALL_BOOT_ROOT=</varname> is set for the plugins to the root directory (mount point, usually) of the hierarchy
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where boot-loader entries, kernel images, and associated resources should be placed. Can be overridden by setting <varname>BOOT_ROOT=</varname>.</para>
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<para><varname>KERNEL_INSTALL_LAYOUT=bls|other|...</varname> is set for the plugins to specify the installation layout.
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Defaults to <option>bls</option> if <filename>$BOOT/<replaceable>MACHINE-ID</replaceable></filename> exists, or <option>other</option> otherwise.
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Additional layout names may be defined by convention. If a plugin uses a special layout,
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it's encouraged to declare its own layout name and configure <varname>layout=</varname> in <filename>install.conf</filename> upon initial installation.</para>
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<para><varname>KERNEL_INSTALL_INITRD_GENERATOR=...</varname> is set for plugins to select the initrd generator.
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This should be configured as <varname>initrd_generator=</varname> in <filename>install.conf</filename>.
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</para>
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<para><varname>KERNEL_INSTALL_STAGING_AREA=...</varname> is set for plugins to a path to a directory.
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Plugins may drop files in that directory, and they will be installed as part of the loader entry, based
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on the file name and extension.</para>
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<variablelist>
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<varlistentry>
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<term>bls</term>
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<listitem>
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<para>Standard <ulink url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader Specification</ulink> layout,
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compatible with <citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry>: entries in
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<filename>$BOOT/loader/entries/<replaceable>MACHINE-ID</replaceable>-<replaceable>KERNEL-VERSION</replaceable>[+<replaceable>TRIES</replaceable>].conf</filename>,
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kernel and initrds under <filename>$BOOT/<replaceable>MACHINE-ID</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/</filename></para>
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<para>Provided by <filename>90-loaderentry.install</filename>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>other</term>
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<listitem>
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<para>Some other layout not understood natively by <command>kernel-install</command>.</para>
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</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>Exit status</title>
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<para>If every executable returns 0 or 77, 0 is returned, and a non-zero failure code otherwise.</para>
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</refsect1>
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<refsect1>
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<title>Files</title>
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<variablelist>
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<varlistentry>
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<term>
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<filename>/usr/lib/kernel/install.d/*.install</filename>
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<filename>/etc/kernel/install.d/*.install</filename>
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</term>
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<listitem>
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<para>Drop-in files which are executed by kernel-install.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<filename>/usr/lib/kernel/cmdline</filename>
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<filename>/etc/kernel/cmdline</filename>
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<filename>/proc/cmdline</filename>
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</term>
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<listitem>
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<para>Read by <filename>90-loaderentry.install</filename>. The content of the file
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<filename>/etc/kernel/cmdline</filename> specifies the kernel command line to use. If that file does not
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exist, <filename>/usr/lib/kernel/cmdline</filename> is used. If that also does not exist,
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<filename>/proc/cmdline</filename> is used.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<filename>/etc/kernel/tries</filename>
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</term>
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<listitem>
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<para>Read by <filename>90-loaderentry.install</filename>. If this file exists a numeric value is read from
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it and the naming of the generated entry file is slightly altered to include it as
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<filename>$BOOT/loader/entries/<replaceable>MACHINE-ID</replaceable>-<replaceable>KERNEL-VERSION</replaceable>+<replaceable>TRIES</replaceable>.conf</filename>. This
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is useful for boot loaders such as
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<citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry> which
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implement boot attempt counting with a counter embedded in the entry file name.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<filename>/etc/machine-id</filename>
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</term>
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<listitem>
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<para>The content of this file specifies the machine identification
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<replaceable>MACHINE-ID</replaceable>. If <filename>/etc/machine-id</filename>
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cannot be read or is temporary (backed by a file on <constant>tmpfs</constant>),
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<command>kernel-install</command> will use <literal>Default</literal> instead.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<filename>/etc/machine-info</filename>
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</term>
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<listitem>
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<para>If this file contains the <varname>KERNEL_INSTALL_MACHINE_ID</varname> variable,
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<command>kernel-install</command> will use it as <replaceable>MACHINE-ID</replaceable> instead of
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the contents of <filename>/etc/machine-id</filename>. If the variable is not found in
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<filename>/etc/machine-info</filename>, <command>kernel-install</command> will try to save the
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machine ID it uses to install to <varname>$BOOT</varname> to this file.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<filename>/etc/os-release</filename>
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<filename>/usr/lib/os-release</filename>
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</term>
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<listitem>
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<para>Read by <filename>90-loaderentry.install</filename>.
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If available, <varname>PRETTY_NAME</varname> is read from these files and used as the title of the boot menu entry.
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Otherwise, <literal>Linux <replaceable>KERNEL-VERSION</replaceable></literal> will be used.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<filename>/usr/lib/kernel/install.conf</filename>
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<filename>/etc/kernel/install.conf</filename>
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</term>
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<listitem>
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<para>Configuration options for <command>kernel-install</command>,
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as a series of <varname>KEY=</varname><replaceable>VALUE</replaceable> assignments,
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compatible with shell syntax.
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See the Environment variables section for supported keys.</para>
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</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>See Also</title>
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<para>
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<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>depmod</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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<ulink url="https://systemd.io/BOOT_LOADER_SPECIFICATION">Boot Loader Specification</ulink>
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</para>
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</refsect1>
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</refentry>
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