man/kernel-install.xml

   1 <?xml version='1.0'?>
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
   5
   6 <refentry id="kernel-install" conditional='ENABLE_KERNEL_INSTALL'
   7           xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>kernel-install</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>kernel-install</refentrytitle>
  16     <manvolnum>8</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>kernel-install</refname>
  21     <refpurpose>Add and remove kernel and initrd images to and from /boot</refpurpose>
  22   </refnamediv>
  23
  24   <refsynopsisdiv>
  25     <cmdsynopsis>
  26       <command>kernel-install</command>
  27       <arg choice="opt" rep="repeat">OPTIONS</arg>
  28       <arg choice="plain">add</arg>
  29       <arg choice="plain"><replaceable>KERNEL-VERSION</replaceable></arg>
  30       <arg choice="plain"><replaceable>KERNEL-IMAGE</replaceable></arg>
  31       <arg choice="opt" rep="repeat"><replaceable>INITRD-FILE</replaceable></arg>
  32     </cmdsynopsis>
  33     <cmdsynopsis>
  34       <command>kernel-install</command>
  35       <arg choice="opt" rep="repeat">OPTIONS</arg>
  36       <arg choice="plain">remove</arg>
  37       <arg choice="plain"><replaceable>KERNEL-VERSION</replaceable></arg>
  38     </cmdsynopsis>
  39     <cmdsynopsis>
  40       <command>kernel-install</command>
  41       <arg choice="opt" rep="repeat">OPTIONS</arg>
  42       <arg choice="plain">inspect</arg>
  43       <arg choice="opt"><replaceable>KERNEL-IMAGE</replaceable></arg>
  44     </cmdsynopsis>
  45   </refsynopsisdiv>
  46
  47   <refsect1>
  48     <title>Description</title>
  49     <para><command>kernel-install</command> is used to install and remove kernel and initrd images
  50     <footnote>
  51       <para>Nowadays actually CPIO archives used as an "initramfs", rather than "initrd". See
  52       <citerefentry><refentrytitle>bootup</refentrytitle><manvolnum>7</manvolnum></citerefentry> for an
  53       explanation.</para>
  54     </footnote>
  55     to and from the boot loader partition, referred to as <varname>$BOOT</varname> here. It will usually be
  56     one of <filename>/boot/</filename>, <filename>/efi/</filename>, or <filename>/boot/efi/</filename>, see
  57     below.</para>
  58
  59     <para><command>kernel-install</command> will run the executable files ("plugins") located in the
  60     directory <filename>/usr/lib/kernel/install.d/</filename> and the local administration directory
  61     <filename>/etc/kernel/install.d/</filename>.  All files are collectively sorted and executed in lexical
  62     order, regardless of the directory in which they live. However, files with identical filenames replace
  63     each other.  Files in <filename>/etc/kernel/install.d/</filename> take precedence over files with the
  64     same name in <filename>/usr/lib/kernel/install.d/</filename>. This can be used to override a
  65     system-supplied executables with a local file if needed; a symbolic link in
  66     <filename>/etc/kernel/install.d/</filename> with the same name as an executable in
  67     <filename>/usr/lib/kernel/install.d/</filename>, pointing to <filename>/dev/null</filename>, disables the
  68     executable entirely. Executables must have the extension <literal>.install</literal>; other extensions
  69     are ignored.</para>
  70
  71     <para>An executable placed in these directories should return <constant>0</constant> on success. It may
  72     also return <constant>77</constant> to cause the whole operation to terminate (executables later in
  73     lexical order will be skipped).</para>
  74   </refsect1>
  75
  76   <refsect1>
  77     <title>Commands</title>
  78     <para>The following commands are understood:</para>
  79     <variablelist>
  80       <varlistentry>
  81         <term>
  82           <command>add</command>
  83           <replaceable>KERNEL-VERSION</replaceable>
  84           <replaceable>KERNEL-IMAGE</replaceable> [<replaceable>INITRD-FILE</replaceable> ...]
  85         </term>
  86
  87         <listitem>
  88           <para>This command expects a kernel version string and a path to a kernel image file as arguments.
  89           Optionally, one or more initrd images may be specified as well (note that plugins might generate
  90           additional ones).</para>
  91
  92           <para>The executable files from <filename>/usr/lib/kernel/install.d/*.install</filename> and
  93           <filename>/etc/kernel/install.d/*.install</filename> (i.e. the plugins) are called with the
  94           following arguments:</para>
  95
  96           <programlisting>add <replaceable>KERNEL-VERSION</replaceable> <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/</filename> <replaceable>KERNEL-IMAGE</replaceable> \
  97           [<replaceable>INITRD-FILE</replaceable> ...]</programlisting>
  98
  99           <para>The third argument directly refers to the path where to place kernel images, initrd
 100           images and other resources for
 101           <ulink url="https://uapi-group.org/specifications/specs/boot_loader_specification">Boot
 102           Loader Specification</ulink> Type #1 entries (the "entry directory"). If other boot loader schemes
 103           are used the parameter may be ignored.</para>
 104
 105           <para>The <replaceable>ENTRY-TOKEN</replaceable> string is typically the machine ID and is supposed
 106           to identify the local installation on the system. For details see below.</para>
 107
 108           <para>Two default plugins execute the following operations in this case:</para>
 109
 110           <itemizedlist>
 111             <listitem><para><command>kernel-install</command> creates
 112             <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable>/<replaceable>KERNEL-VERSION</replaceable></filename>,
 113             if enabled (see <varname>$KERNEL_INSTALL_LAYOUT</varname>).</para></listitem>
 114
 115             <listitem><para><filename>50-depmod.install</filename> runs
 116             <citerefentry project='man-pages'><refentrytitle>depmod</refentrytitle><manvolnum>8</manvolnum></citerefentry> for the
 117             <replaceable>KERNEL-VERSION</replaceable>.</para></listitem>
 118
 119             <listitem><para><filename>90-loaderentry.install</filename> copies
 120             <replaceable>KERNEL-IMAGE</replaceable> to
 121             <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/linux</filename>.
 122             If <replaceable>INITRD-FILE</replaceable>s are provided, it also copies them to
 123             <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable>/<replaceable>KERNEL_VERSION</replaceable>/<replaceable>INITRD-FILE</replaceable></filename>.
 124             This can also be used to prepend microcode before the actual initrd. It also creates a boot loader entry according to the <ulink
 125             url="https://uapi-group.org/specifications/specs/boot_loader_specification">Boot Loader Specification</ulink> (Type #1) in
 126             <filename>$BOOT/loader/entries/<replaceable>ENTRY-TOKEN</replaceable>-<replaceable>KERNEL-VERSION</replaceable>.conf</filename>.
 127             The title of the entry is the <replaceable>PRETTY_NAME</replaceable> parameter specified in
 128             <filename>/etc/os-release</filename> or <filename>/usr/lib/os-release</filename> (if the former
 129             is missing), or "Linux <replaceable>KERNEL-VERSION</replaceable>", if unset.</para>
 130
 131             <para>If <varname>$KERNEL_INSTALL_LAYOUT</varname> is not "bls", this plugin does nothing.</para></listitem>
 132
 133             <listitem><para><filename>90-uki-copy.install</filename> copies a file
 134             <filename>uki.efi</filename> from <varname>$KERNEL_INSTALL_STAGING_AREA</varname> or if it does
 135             not exist the <replaceable>KERNEL-IMAGE</replaceable> argument, only if it has a
 136             <literal>.efi</literal> extension, to
 137             <filename>$BOOT/EFI/Linux/<replaceable>ENTRY-TOKEN</replaceable>-<replaceable>KERNEL-VERSION</replaceable>.efi</filename>.</para>
 138
 139             <para>If <varname>$KERNEL_INSTALL_LAYOUT</varname> is not "uki", this plugin does nothing.</para></listitem>
 140           </itemizedlist>
 141
 142             <xi:include href="version-info.xml" xpointer="v198"/>
 143         </listitem>
 144       </varlistentry>
 145       <varlistentry>
 146         <term><command>remove <replaceable>KERNEL-VERSION</replaceable></command></term>
 147         <listitem>
 148           <para>This command expects a kernel version string as single argument.</para>
 149
 150           <para>The executable files from <filename>/usr/lib/kernel/install.d/*.install</filename> and
 151           <filename>/etc/kernel/install.d/*.install</filename> (i.e. the plugins) are called with the
 152           following arguments:</para>
 153
 154           <programlisting>remove <replaceable>KERNEL-VERSION</replaceable> <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/</filename></programlisting>
 155
 156           <para>Afterwards, <command>kernel-install</command> removes the entry directory
 157           <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/</filename>
 158           and its contents, if it exists.</para>
 159
 160           <para>Two default plugins execute the following operations in this case:</para>
 161
 162           <itemizedlist>
 163             <listitem><para><filename>50-depmod.install</filename> removes the files generated by
 164             <command>depmod</command> for this kernel again.</para></listitem>
 165
 166             <listitem><para><filename>90-loaderentry.install</filename> removes the file
 167             <filename>$BOOT/loader/entries/<replaceable>ENTRY-TOKEN</replaceable>-<replaceable>KERNEL-VERSION</replaceable>.conf</filename>.
 168             </para></listitem>
 169
 170             <listitem><para><filename>90-uki-copy.install</filename> removes the file
 171             <filename>$BOOT/EFI/Linux/<replaceable>ENTRY-TOKEN</replaceable>-<replaceable>KERNEL-VERSION</replaceable>.efi</filename>.
 172             </para></listitem>
 173           </itemizedlist>
 174
 175             <xi:include href="version-info.xml" xpointer="v198"/>
 176         </listitem>
 177       </varlistentry>
 178       <varlistentry>
 179         <term><command>inspect [<replaceable>KERNEL-IMAGE</replaceable>]</command></term>
 180         <listitem>
 181           <para>Shows the various paths and parameters configured or auto-detected. In particular shows the
 182           values of the various <varname>$KERNEL_INSTALL_*</varname> environment variables listed
 183           below.</para>
 184
 185           <xi:include href="version-info.xml" xpointer="v251"/>
 186         </listitem>
 187       </varlistentry>
 188
 189     </variablelist>
 190   </refsect1>
 191
 192   <refsect1>
 193     <title>The <varname>$BOOT</varname> partition</title>
 194
 195     <para>The partition where the kernels and <ulink url="https://uapi-group.org/specifications/specs/boot_loader_specification">Boot
 196     Loader Specification</ulink> snippets are located is called <varname>$BOOT</varname>.
 197     <command>kernel-install</command> determines the location of this partition by checking
 198     <filename>/efi/</filename>, <filename>/boot/</filename>, and <filename>/boot/efi/</filename> in turn. The
 199     first location where <filename>$BOOT/loader/entries/</filename> or
 200     <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable>/</filename> exists is used.</para>
 201   </refsect1>
 202
 203   <refsect1>
 204     <title>Options</title>
 205     <para>The following options are understood:</para>
 206
 207     <variablelist>
 208       <xi:include href="standard-options.xml" xpointer="esp-path"/>
 209       <xi:include href="standard-options.xml" xpointer="boot-path"/>
 210
 211       <varlistentry>
 212         <term><option>--make-entry-directory=yes|no|auto</option></term>
 213         <listitem>
 214           <para>Controls creation and deletion of the
 215           <ulink url="https://uapi-group.org/specifications/specs/boot_loader_specification">Boot Loader Specification</ulink>
 216           Type #1 entry directory on the file system containing resources such as kernel and initrd images
 217           during <option>add</option> and <option>remove</option>, respectively. The directory is named after
 218           the entry token, and is placed immediately below the boot root directory. When
 219           <literal>auto</literal>, the directory is created or removed only when the install layout is
 220           <literal>bls</literal>. Defaults to <literal>auto</literal>.</para>
 221
 222           <xi:include href="version-info.xml" xpointer="v254"/>
 223         </listitem>
 224       </varlistentry>
 225
 226       <varlistentry>
 227         <term><option>--entry-token=</option></term>
 228
 229         <listitem>
 230           <para>Controls how to name and identify boot loader entries for this kernel installation or
 231           deletion. Takes one of <literal>auto</literal>, <literal>machine-id</literal>,
 232           <literal>os-id</literal>, <literal>os-image-id</literal>, or an arbitrary string prefixed by
 233           <literal>literal:</literal> as argument.</para>
 234
 235           <para>If set to <option>machine-id</option> the entries are named after the machine ID of the
 236           running system (e.g. <literal>b0e793a9baf14b5fa13ecbe84ff637ac</literal>). See
 237           <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
 238           details about the machine ID concept and file.</para>
 239
 240           <para>If set to <option>os-id</option> the entries are named after the OS ID of the running system,
 241           i.e. the <varname>ID=</varname> field of
 242           <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 243           (e.g. <literal>fedora</literal>). Similarly, if set to <option>os-image-id</option> the entries are
 244           named after the OS image ID of the running system, i.e. the <varname>IMAGE_ID=</varname> field of
 245           <filename>os-release</filename> (e.g. <literal>vendorx-cashier-system</literal>).</para>
 246
 247           <para>If set to <option>auto</option> (the default), the
 248           <filename>/etc/kernel/entry-token</filename> (or
 249           <filename>$KERNEL_INSTALL_CONF_ROOT/entry-token</filename>) file will be read if it exists, and the
 250           stored value used. Otherwise if the local machine ID is initialized it is used. Otherwise
 251           <varname>IMAGE_ID=</varname> from <filename>os-release</filename> will be used, if set. Otherwise,
 252           <varname>ID=</varname> from <filename>os-release</filename> will be used, if set. Otherwise a
 253           randomly generated machine ID is used.</para>
 254
 255           <para>Using the machine ID for naming the entries is generally preferable, however there are cases
 256           where using the other identifiers is a good option. Specifically: if the identification data that
 257           the machine ID entails shall not be stored on the (unencrypted) <varname>$BOOT_ROOT</varname>
 258           partition, or if the ID shall be generated on first boot and is not known when the entries are
 259           prepared. Note that using the machine ID has the benefit that multiple parallel installations of
 260           the same OS can coexist on the same medium, and they can update their boot loader entries
 261           independently. When using another identifier (such as the OS ID or the OS image ID), parallel
 262           installations of the same OS would try to use the same entry name. To support parallel
 263           installations, the installer must use a different entry token when adding a second installation.
 264           </para>
 265
 266           <xi:include href="version-info.xml" xpointer="v254"/>
 267         </listitem>
 268       </varlistentry>
 269
 270       <varlistentry>
 271         <term><option>-v</option></term>
 272         <term><option>--verbose</option></term>
 273         <listitem>
 274           <para>Output additional information about operations being performed.</para>
 275
 276         <xi:include href="version-info.xml" xpointer="v242"/>
 277         </listitem>
 278       </varlistentry>
 279
 280       <xi:include href="standard-options.xml" xpointer="help" />
 281       <xi:include href="standard-options.xml" xpointer="version" />
 282     </variablelist>
 283   </refsect1>
 284
 285   <refsect1>
 286     <title>Environment variables</title>
 287
 288     <refsect2>
 289       <title>Environment variables exported for plugins</title>
 290
 291       <para>If <option>--verbose</option> is used, <varname>$KERNEL_INSTALL_VERBOSE=1</varname> will be
 292       exported for plugins. They may output additional logs in this case.</para>
 293
 294       <para><varname>$KERNEL_INSTALL_MACHINE_ID</varname> is set for the plugins to the desired machine-id to
 295       use. It's always a 128-bit ID. Normally it's read from <filename>/etc/machine-id</filename>, but it can
 296       also be overridden via <varname>$MACHINE_ID</varname> (see below). If not specified via these methods,
 297       a fallback value will generated by <command>kernel-install</command> and used only for a single
 298       invocation.</para>
 299
 300       <para><varname>$KERNEL_INSTALL_ENTRY_TOKEN</varname> is set for the plugins to the desired entry
 301       "token" to use. It's an identifier that shall be used to identify the local installation, and is often
 302       the machine ID, i.e. same as <varname>$KERNEL_INSTALL_MACHINE_ID</varname>, but might also be a
 303       different type of identifier, for example a fixed string or the <varname>ID=</varname>,
 304       <varname>IMAGE_ID=</varname> values from <filename>/etc/os-release</filename>. The string passed here
 305       will be used to name Boot Loader Specification entries, or the directories the kernel image and initial
 306       RAM disk images are placed into.</para>
 307
 308       <para>Note that while <varname>$KERNEL_INSTALL_ENTRY_TOKEN</varname> and
 309       <varname>$KERNEL_INSTALL_MACHINE_ID</varname> are often set to the same value, the latter is guaranteed
 310       to be a valid 32 character ID in lowercase hexadecimals while the former can be any short string. The
 311       entry token to use is read from <filename>/etc/kernel/entry-token</filename>, if it exists. Otherwise a
 312       few possible candidates below <varname>$BOOT</varname> are checked for Boot Loader Specification Type 1
 313       entry directories, and if found the entry token is derived from that. If that is not successful,
 314       <varname>$KERNEL_INSTALL_MACHINE_ID</varname> is used as fallback.</para>
 315
 316       <para><varname>$KERNEL_INSTALL_BOOT_ROOT</varname> is set for the plugins to the absolute path of the
 317       root directory (mount point, usually) of the hierarchy where boot loader entries, kernel images, and
 318       associated resources should be placed. This usually is the path where the XBOOTLDR partition or the ESP
 319       (EFI System Partition) are mounted, and also conceptually referred to as <varname>$BOOT</varname>. Can
 320       be overridden by setting <varname>$BOOT_ROOT</varname> (see below).</para>
 321
 322       <para><varname>$KERNEL_INSTALL_LAYOUT=auto|bls|uki|other|...</varname> is set for the plugins to specify the
 323       installation layout. Additional layout names may be defined by convention. If a plugin uses a special layout,
 324       it's encouraged to declare its own layout name and configure <varname>layout=</varname> in
 325       <filename>install.conf</filename> upon initial installation. The following values are currently
 326       understood:</para>
 327
 328       <variablelist>
 329         <varlistentry>
 330           <term>bls</term>
 331           <listitem>
 332             <para>Standard <ulink url="https://uapi-group.org/specifications/specs/boot_loader_specification">Boot Loader
 333             Specification</ulink> Type #1 layout, compatible with
 334             <citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry>:
 335             entries in
 336             <filename>$BOOT/loader/entries/<replaceable>ENTRY-TOKEN</replaceable>-<replaceable>KERNEL-VERSION</replaceable>[+<replaceable>TRIES</replaceable>].conf</filename>,
 337             kernel and initrds under
 338             <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable>/<replaceable>KERNEL-VERSION</replaceable>/</filename></para>
 339             <para>Implemented by <filename>90-loaderentry.install</filename>.</para>
 340
 341             <xi:include href="version-info.xml" xpointer="v250"/>
 342           </listitem>
 343         </varlistentry>
 344         <varlistentry>
 345           <term>uki</term>
 346           <listitem>
 347             <para>Standard <ulink
 348             url="https://uapi-group.org/specifications/specs/boot_loader_specification">Boot Loader
 349             Specification</ulink> Type #2 layout, compatible with
 350             <citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry>:
 351             unified kernel images under <filename>$BOOT/EFI/Linux</filename> as
 352             <filename>$BOOT/EFI/Linux/<replaceable>ENTRY-TOKEN</replaceable>-<replaceable>KERNEL-VERSION</replaceable>[+<replaceable>TRIES</replaceable>].efi</filename>.</para>
 353             <para>Implemented by <filename>90-uki-copy.install</filename>.</para>
 354
 355             <xi:include href="version-info.xml" xpointer="v253"/>
 356           </listitem>
 357         </varlistentry>
 358         <varlistentry>
 359           <term>other</term>
 360           <listitem>
 361             <para>Some other layout not understood natively by <command>kernel-install</command>.</para>
 362
 363           <xi:include href="version-info.xml" xpointer="v250"/>
 364           </listitem>
 365         </varlistentry>
 366         <varlistentry>
 367           <term>auto</term>
 368           <listitem>
 369             <para>Pick the layout automatically. If the kernel is a UKI set layout to
 370             <option>uki</option>. If not default to <option>bls</option> if
 371             <filename>$BOOT/loader/entries.srel</filename> with content <literal>type1</literal> or
 372             <filename>$BOOT/<replaceable>ENTRY-TOKEN</replaceable></filename> exists, or
 373             <option>other</option> otherwise.</para>
 374             <para>Leaving layout blank has the same effect. This is the default.</para>
 375
 376             <xi:include href="version-info.xml" xpointer="v254"/>
 377           </listitem>
 378         </varlistentry>
 379       </variablelist>
 380
 381       <para><varname>$KERNEL_INSTALL_INITRD_GENERATOR</varname> and <varname>$KERNEL_INSTALL_UKI_GENERATOR</varname>
 382       are set for plugins to select the initrd and/or UKI generator. This may be configured as
 383       <varname>initrd_generator=</varname> and <varname>uki_generator=</varname> in <filename>install.conf</filename>, see below.</para>
 384
 385       <para><varname>$KERNEL_INSTALL_STAGING_AREA</varname> is set for plugins to a path to a directory.
 386       Plugins may drop files in that directory, and they will be installed as part of the loader entry, based
 387       on the file name and extension: Files named <filename>initrd*</filename> will be installed as <replaceable>INITRD-FILE</replaceable>s,
 388       and files named <filename>microcode*</filename> will be prepended before <replaceable>INITRD-FILE</replaceable>s.</para>
 389
 390     </refsect2>
 391
 392     <refsect2>
 393       <title>Environment variables understood by <command>kernel-install</command></title>
 394
 395       <para><varname>$KERNEL_INSTALL_CONF_ROOT</varname> can be set to override the location of the
 396       configuration files read by <command>kernel-install</command>. When set,
 397       <filename>install.conf</filename>, <filename>entry-token</filename>, and other files will be
 398       read from this directory.</para>
 399
 400       <para><varname>$KERNEL_INSTALL_PLUGINS</varname> can be set to override the list of plugins executed by
 401       <command>kernel-install</command>. The argument is a whitespace-separated list of paths.
 402       <literal>KERNEL_INSTALL_PLUGINS=:</literal> may be used to prevent any plugins from running.
 403       </para>
 404
 405       <para><varname>$MACHINE_ID</varname> can be set for <command>kernel-install</command> to override
 406       <varname>$KERNEL_INSTALL_MACHINE_ID</varname>, the machine ID.</para>
 407
 408       <para><varname>$BOOT_ROOT</varname> can be set for <command>kernel-install</command> to override
 409       <varname>$KERNEL_INSTALL_BOOT_ROOT</varname>, the installation location for boot entries.</para>
 410
 411       <para>The last two variables may also be set in <filename>install.conf</filename>. Variables set in the
 412       environment take precedence over the values specified in the config file.</para>
 413     </refsect2>
 414   </refsect1>
 415
 416   <refsect1>
 417     <title>Exit status</title>
 418     <para>If every executable returns 0 or 77, 0 is returned, and a non-zero failure code otherwise.</para>
 419   </refsect1>
 420
 421   <refsect1>
 422     <title>Files</title>
 423     <variablelist>
 424       <varlistentry>
 425         <term>
 426           <filename>/usr/lib/kernel/install.d/*.install</filename>
 427           <filename>/etc/kernel/install.d/*.install</filename>
 428         </term>
 429           <listitem>
 430             <para>Drop-in files which are executed by kernel-install.</para>
 431
 432           <xi:include href="version-info.xml" xpointer="v198"/>
 433           </listitem>
 434       </varlistentry>
 435       <varlistentry>
 436         <term>
 437           <filename>/usr/lib/kernel/cmdline</filename>
 438           <filename>/etc/kernel/cmdline</filename>
 439           <filename>/proc/cmdline</filename>
 440         </term>
 441           <listitem>
 442             <para>Read by <filename>90-loaderentry.install</filename>. The content of the file
 443             <filename>/etc/kernel/cmdline</filename> specifies the kernel command line to use. If that file
 444             does not exist, <filename>/usr/lib/kernel/cmdline</filename> is used. If that also does not
 445             exist, <filename>/proc/cmdline</filename> is used. <varname>$KERNEL_INSTALL_CONF_ROOT</varname>
 446             may be used to override the path.</para>
 447
 448           <xi:include href="version-info.xml" xpointer="v198"/>
 449           </listitem>
 450       </varlistentry>
 451       <varlistentry>
 452         <term>
 453           <filename>/etc/kernel/tries</filename>
 454         </term>
 455           <listitem>
 456             <para>Read by <filename>90-loaderentry.install</filename> and
 457             <filename>90-uki-copy.install</filename>. If this file exists a numeric value is read from it
 458             and the naming of the generated entry file or UKI is slightly altered to include it as
 459             <filename>$BOOT/loader/entries/<replaceable>ENTRY-TOKEN</replaceable>-<replaceable>KERNEL-VERSION</replaceable>+<replaceable>TRIES</replaceable>.conf</filename>
 460             or
 461             <filename>$BOOT/EFI/Linux/<replaceable>ENTRY-TOKEN</replaceable>-<replaceable>KERNEL-VERSION</replaceable>+<replaceable>TRIES</replaceable>.efi</filename>, respectively. This
 462             is useful for boot loaders such as
 463             <citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 464             which implement boot attempt counting with a counter embedded in the entry file name.
 465             <varname>$KERNEL_INSTALL_CONF_ROOT</varname> may be used to override the path.</para>
 466
 467           <xi:include href="version-info.xml" xpointer="v240"/>
 468           </listitem>
 469       </varlistentry>
 470       <varlistentry>
 471         <term>
 472           <filename>/etc/kernel/entry-token</filename>
 473         </term>
 474           <listitem>
 475             <para>If this file exists it is read and used as "entry token" for this system, i.e. is used for
 476             naming Boot Loader Specification entries, see <varname>$KERNEL_INSTALL_ENTRY_TOKEN</varname>
 477             above for details. <varname>$KERNEL_INSTALL_CONF_ROOT</varname> may be used to override the
 478             path.</para>
 479
 480             <xi:include href="version-info.xml" xpointer="v251"/>
 481           </listitem>
 482       </varlistentry>
 483       <varlistentry>
 484         <term>
 485           <filename>/etc/machine-id</filename>
 486         </term>
 487           <listitem>
 488             <para>The content of this file specifies the machine identification
 489             <replaceable>MACHINE-ID</replaceable>.</para>
 490
 491             <xi:include href="version-info.xml" xpointer="v198"/>
 492           </listitem>
 493       </varlistentry>
 494       <varlistentry>
 495         <term>
 496           <filename>/etc/os-release</filename>
 497           <filename>/usr/lib/os-release</filename>
 498         </term>
 499         <listitem>
 500             <para>Read by <filename>90-loaderentry.install</filename>.
 501             If available, <varname>PRETTY_NAME=</varname> is read from these files and used as the title of the boot menu entry.
 502             Otherwise, <literal>Linux <replaceable>KERNEL-VERSION</replaceable></literal> will be used.</para>
 503
 504         <xi:include href="version-info.xml" xpointer="v198"/>
 505           </listitem>
 506       </varlistentry>
 507       <varlistentry>
 508         <term>
 509           <filename>/usr/lib/kernel/install.conf</filename>
 510           <filename>/etc/kernel/install.conf</filename>
 511         </term>
 512           <listitem>
 513             <para>Configuration options for <command>kernel-install</command>, as a series of
 514             <varname>KEY=</varname><replaceable>VALUE</replaceable> assignments, compatible with shell
 515             syntax, following the same rules as described in
 516             <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 517             <filename>/etc/kernel/install.conf</filename> will be read if present, and
 518             <filename>/usr/lib/kernel/install.conf</filename> otherwise. This file is optional.
 519             <varname>$KERNEL_INSTALL_CONF_ROOT</varname> may be used to override the path.
 520             </para>
 521
 522             <para>Currently, the following keys are supported:
 523             <varname>MACHINE_ID=</varname>,
 524             <varname>BOOT_ROOT=</varname>,
 525             <varname>layout=</varname>,
 526             <varname>initrd_generator=</varname>,
 527             <varname>uki_generator=</varname>.
 528             See the Environment variables section above for details.</para>
 529
 530             <xi:include href="version-info.xml" xpointer="v250"/>
 531           </listitem>
 532       </varlistentry>
 533       <varlistentry>
 534         <term>
 535           <filename>/etc/kernel/uki.conf</filename>
 536         </term>
 537           <listitem>
 538             <para>Ini-style configuration file for
 539             <citerefentry><refentrytitle>ukify</refentrytitle><manvolnum>1</manvolnum></citerefentry> which
 540             is only effective when <varname>$KERNEL_INSTALL_LAYOUT</varname> or <varname>layout=</varname> in
 541             <filename>install.conf</filename> is set to <option>uki</option> and
 542             <varname>$KERNEL_INSTALL_UKI_GENERATOR</varname> or <varname>uki_generator=</varname> in
 543             <filename>install.conf</filename> is set to <option>ukify</option>.
 544             <varname>$KERNEL_INSTALL_CONF_ROOT</varname> may be used to override the path.
 545             </para>
 546
 547             <xi:include href="version-info.xml" xpointer="v255"/>
 548           </listitem>
 549       </varlistentry>
 550     </variablelist>
 551   </refsect1>
 552
 553   <refsect1>
 554     <title>See Also</title>
 555     <para>
 556       <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 557       <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 558       <citerefentry project='man-pages'><refentrytitle>depmod</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 559       <citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 560       <citerefentry><refentrytitle>ukify</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 561       <ulink url="https://uapi-group.org/specifications/specs/boot_loader_specification">Boot Loader Specification</ulink>
 562     </para>
 563   </refsect1>
 564
 565 </refentry>