KERNEL-INSTALL(8)		kernel-install		     KERNEL-INSTALL(8)

NAME
       kernel-install - Add and remove kernel and initrd images to and from
       the boot partition

SYNOPSIS
       kernel-install [OPTIONS...] add KERNEL-VERSION KERNEL-IMAGE
		      [INITRD-FILE...]

       kernel-install [OPTIONS...] add-all

       kernel-install [OPTIONS...] remove KERNEL-VERSION

       kernel-install [OPTIONS...] inspect [KERNEL-VERSION] [KERNEL-IMAGE]
		      [INITRD-FILE...]

       kernel-install [OPTIONS...] list

DESCRIPTION
       kernel-install is used to install and remove kernel and initrd images
       [1] to and from the boot partition, referred to as $BOOT here. It will
       usually be one of /boot/, /efi/, or /boot/efi/, see below.

       kernel-install will run the executable files ("plugins") located in the
       directory /usr/lib/kernel/install.d/ and the local administration
       directory /etc/kernel/install.d/. 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 /etc/kernel/install.d/ take precedence over files with the same name
       in /usr/lib/kernel/install.d/. This can be used to override a
       system-supplied executables with a local file if needed; a symbolic
       link in /etc/kernel/install.d/ with the same name as an executable in
       /usr/lib/kernel/install.d/, pointing to /dev/null, disables the
       executable entirely. Executables must have the extension ".install";
       other extensions are ignored.

       An executable placed in these directories should return 0 on success.
       It may also return 77 to cause the whole operation to terminate
       (executables later in lexical order will be skipped).

COMMANDS
       The following commands are understood:

       add [[[KERNEL-VERSION] KERNEL-IMAGE] [INITRD-FILE ...]]
	   This command takes a kernel version string and a path to a kernel
	   image file as arguments. If the former is omitted, specified as an
	   empty string or as "-" it defaults to the current kernel version,
	   i.e. the same string uname -r returns. If the latter is omitted,
	   specified as an empty string or as "-" defaults to
	   /usr/lib/modules/KERNEL_VERSION/vmlinuz. Optionally, one or more
	   initrd images may be specified as well (note that plugins might
	   generate additional ones).

	   The executable files from /usr/lib/kernel/install.d/*.install and
	   /etc/kernel/install.d/*.install (i.e. the plugins) are called with
	   the following arguments:

	       add KERNEL-VERSION $BOOT/ENTRY-TOKEN/KERNEL-VERSION/ KERNEL-IMAGE [INITRD-FILE ...]

	   The third argument directly refers to the path where to place
	   kernel images, initrd images and other resources for Boot Loader
	   Specification[2] Type #1 entries (the "entry directory"). If other
	   boot loader schemes are used the parameter may be ignored.

	   The ENTRY-TOKEN string is typically the machine ID and is supposed
	   to identify the local installation on the system. For details see
	   below.

	   kernel-install creates $BOOT/ENTRY-TOKEN/KERNEL-VERSION, if enabled
	   (see $KERNEL_INSTALL_LAYOUT).

	   Three default plugins execute the following operations in this
	   case:

	   50-depmod.install
	       The plugin runs depmod(8) for the KERNEL-VERSION.

	   90-loaderentry.install
	       The plugin copies KERNEL-IMAGE to
	       $BOOT/ENTRY-TOKEN/KERNEL-VERSION/linux. If INITRD-FILEs are
	       provided, it also copies them to
	       $BOOT/ENTRY-TOKEN/KERNEL_VERSION/INITRD-FILE. This can also be
	       used to prepend microcode before the actual initrd. It also
	       creates a boot loader entry according to the Boot Loader
	       Specification[2] (Type #1) in
	       $BOOT/loader/entries/ENTRY-TOKEN-KERNEL-VERSION.conf. The title
	       of the entry is the PRETTY_NAME parameter specified in
	       /etc/os-release or /usr/lib/os-release (if the former is
	       missing), or "Linux KERNEL-VERSION", if unset.

	       If $KERNEL_INSTALL_LAYOUT is not "bls", this plugin does
	       nothing.

	   90-uki-copy.install
	       If $KERNEL_INSTALL_STAGING_AREA/uki.efi exists, the plugin
	       copies it to $BOOT/EFI/Linux/ENTRY-TOKEN-KERNEL-VERSION.efi.
	       Also, files in $KERNEL_INSTALL_STAGING_AREA/uki.efi.extra.d"/
	       are copied to
	       $BOOT/EFI/Linux/ENTRY-TOKEN-KERNEL-VERSION.efi.extra.d/.

	       If $KERNEL_INSTALL_STAGING_AREA/uki.efi does not exist, and the
	       KERNEL-IMAGE argument has a ".efi" extension, the plugin copies
	       the image to $BOOT/EFI/Linux/ENTRY-TOKEN-KERNEL-VERSION.efi.
	       Also, files in KERNEL-IMAGE.extra.d/ and
	       $KERNEL_INSTALL_STAGING_AREA/uki.efi.extra.d"/ are copied to
	       $BOOT/EFI/Linux/ENTRY-TOKEN-KERNEL-VERSION.efi.extra.d/.

	       If $KERNEL_INSTALL_LAYOUT is not "uki", this plugin does
	       nothing.

	   Added in version 198.

       add-all
	   This is the same as add (see above), but invokes the operation
	   iteratively for every installed kernel in /usr/lib/modules/. This
	   operation is only supported on systems where the kernel image is
	   installed in /usr/lib/modules/KERNEL-VERSION/vmlinuz.

	   Added in version 255.

       remove KERNEL-VERSION
	   This command expects a kernel version string as single argument.

	   The executable files from /usr/lib/kernel/install.d/*.install and
	   /etc/kernel/install.d/*.install (i.e. the plugins) are called with
	   the following arguments:

	       remove KERNEL-VERSION $BOOT/ENTRY-TOKEN/KERNEL-VERSION/

	   Afterwards, kernel-install removes the entry directory
	   $BOOT/ENTRY-TOKEN/KERNEL-VERSION/ and its contents, if it exists.

	   Three default plugins execute the following operations in this
	   case:

	   50-depmod.install
	       The plugin removes the files generated by depmod for this
	       kernel again.

	   90-loaderentry.install
	       The plugin removes the file
	       $BOOT/loader/entries/ENTRY-TOKEN-KERNEL-VERSION.conf.

	   90-uki-copy.install
	       The plugin removes the file
	       $BOOT/EFI/Linux/ENTRY-TOKEN-KERNEL-VERSION.efi and
	       $BOOT/EFI/Linux/ENTRY-TOKEN-KERNEL-VERSION.efi.extra.d/
	       directory including its contents.

	   Added in version 198.

       inspect [[[KERNEL-VERSION] KERNEL-IMAGE] [INITRD-FILE ...]]
	   Takes the same parameters as add.

	   Shows the various paths and parameters configured or auto-detected.
	   In particular shows the values of the various $KERNEL_INSTALL_*
	   environment variables listed below, as they would be passed to
	   plugins. The --json option can be used to get the output of this
	   verb as a JSON object.

	   Added in version 251.

       list
	   Shows the various installed kernels. This enumerates the
	   subdirectories of /usr/lib/modules/, and shows whether a kernel
	   image is installed there.

	   Added in version 255.

COMPATIBILITY WITH THE KERNEL BUILD SYSTEM
       installkernel [OPTIONS...] VERSION VMLINUZ [MAP] [INSTALLATION-DIR]

       When invoked as installkernel, this program accepts arguments as
       specified by the kernel build system's make install command. The
       VERSION and VMLINUZ parameters specify the kernel version and the
       kernel binary. The other two parameters (MAP and INSTALLATION-DIR) are
       currently ignored.

THE $BOOT PARTITION
       The partition where the kernels and Boot Loader Specification[2]
       snippets are located is called $BOOT.  kernel-install determines the
       location of this partition by checking /efi/, /boot/, and /boot/efi/ in
       turn. The first location where $BOOT/loader/entries/ or
       $BOOT/ENTRY-TOKEN/ exists is used.

OPTIONS
       The following options are understood:

       --esp-path=
	   Path to the EFI System Partition (ESP). If not specified, /efi/,
	   /boot/, and /boot/efi/ are checked in turn. It is recommended to
	   mount the ESP to /efi/, if possible.

       --boot-path=
	   Path to the Extended Boot Loader partition, as defined in the Boot
	   Loader Specification[2]. If not specified, /boot/ is checked. It is
	   recommended to mount the Extended Boot Loader partition to /boot/,
	   if possible.

       --make-entry-directory=yes|no|auto
	   Controls creation and deletion of the Boot Loader Specification[2]
	   Type #1 entry directory on the file system containing resources
	   such as kernel and initrd images during add and remove,
	   respectively. The directory is named after the entry token, and is
	   placed immediately below the boot root directory. When "auto", the
	   directory is created or removed only when the install layout is
	   "bls". Defaults to "auto".

	   Added in version 254.

       --entry-type=type1|type2|all
	   Controls the type of entries handled by the command. This is
	   typically useful when multiple types of boot entries with the same
	   kernel version are installed, and only one should be removed. When
	   "type1" or "type2" is specified, each plugin is invoked with
	   $KERNEL_INSTALL_BOOT_ENTRY_TYPE environment variable with the
	   specified value. When "all" is specified, the environment variable
	   will not be set. Defaults to "all".

	   Added in version 258.

       --entry-token=
	   Controls how to name and identify boot loader entries for this
	   kernel installation or deletion. Takes one of "auto", "machine-id",
	   "os-id", "os-image-id", or an arbitrary string prefixed by
	   "literal:" as argument.

	   If set to machine-id the entries are named after the machine ID of
	   the running system (e.g.  "b0e793a9baf14b5fa13ecbe84ff637ac"). See
	   machine-id(5) for details about the machine ID concept and file.

	   If set to os-id the entries are named after the OS ID of the
	   running system, i.e. the ID= field of os-release(5) (e.g.
	   "fedora"). Similarly, if set to os-image-id the entries are named
	   after the OS image ID of the running system, i.e. the IMAGE_ID=
	   field of os-release (e.g.  "vendorx-cashier-system").

	   If set to auto (the default), the /etc/kernel/entry-token (or
	   $KERNEL_INSTALL_CONF_ROOT/entry-token) file will be read if it
	   exists, and the stored value used. Otherwise, if the local machine
	   ID is initialized, it is used. Otherwise, IMAGE_ID= from os-release
	   will be used, if set. Otherwise, ID= from os-release will be used,
	   if set. Otherwise, a randomly generated machine ID is used.

	   Using the machine ID for naming the entries is generally
	   preferable, however there are cases where using the other
	   identifiers is a good option. Specifically: if the identification
	   data that the machine ID entails shall not be stored on the
	   (unencrypted) $BOOT_ROOT partition, or if the ID shall be generated
	   on first boot and is not known when the entries are prepared. Note
	   that using the machine ID has the benefit that multiple parallel
	   installations of the same OS can coexist on the same medium, and
	   they can update their boot loader entries independently. When using
	   another identifier (such as the OS ID or the OS image ID), parallel
	   installations of the same OS would try to use the same entry name.
	   To support parallel installations, the installer must use a
	   different entry token when adding a second installation.

	   Added in version 254.

       -v, --verbose
	   Output additional information about operations being performed.

	   Added in version 242.

       --root=root
	   Takes a directory path as an argument. All paths will be prefixed
	   with the given alternate root path, including config search paths.
	   This is useful to operate on a system image mounted to the
	   specified directory instead of the host system itself.

	   Added in version 255.

       --image=image
	   Takes a path to a disk image file or block device node. If
	   specified, all operations are applied to the file system in the
	   indicated disk image. This option is similar to --root=, but
	   operates on file systems stored in disk images or block devices.
	   The disk image should either contain just a file system or a set of
	   file systems within a GPT partition table, following the
	   Discoverable Partitions Specification[3]. For further information
	   on supported disk images, see systemd-nspawn(1)'s switch of the
	   same name.

	   Added in version 255.

       -h, --help
	   Print a short help text and exit.

       --version
	   Print a short version string and exit.

       --no-pager
	   Do not pipe output into a pager.

       --json=MODE
	   Shows output formatted as JSON. Expects one of "short" (for the
	   shortest possible output without any redundant whitespace or line
	   breaks), "pretty" (for a pretty version of the same, with
	   indentation and line breaks) or "off" (to turn off JSON output, the
	   default).

       --image-policy=policy
	   Takes an image policy string as argument, as per systemd.image-
	   policy(7). The policy is enforced when operating on the disk image
	   specified via --image=, see above. If not specified, defaults to
	   the "*" policy, i.e. all recognized file systems in the image are
	   used.

       --no-legend
	   Do not print the legend, i.e. column headers and the footer with
	   hints.

ENVIRONMENT VARIABLES
   Environment variables exported for plugins
       If --verbose is used, $KERNEL_INSTALL_VERBOSE=1 will be exported for
       plugins. They may output additional logs in this case.

       $KERNEL_INSTALL_IMAGE_TYPE=uki|pe|unknown is set for the plugins to
       specify the type of the kernel image.

       uki
	   Unified kernel image.

	   Added in version 254.

       pe
	   PE binary.

	   Added in version 254.

       unknown
	   Unknown type.

	   Added in version 254.

       $KERNEL_INSTALL_MACHINE_ID is set for the plugins to the desired
       machine-id to use. It's always a 128-bit ID. Normally it is read from
       /etc/machine-id, but it can also be overridden via $MACHINE_ID (see
       below). If not specified via these methods, a fallback value will
       generated by kernel-install and used only for a single invocation.

       $KERNEL_INSTALL_ENTRY_TOKEN 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
       $KERNEL_INSTALL_MACHINE_ID, but might also be a different type of
       identifier, for example a fixed string or the ID=, IMAGE_ID= values
       from /etc/os-release. 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.

       Note that while $KERNEL_INSTALL_ENTRY_TOKEN and
       $KERNEL_INSTALL_MACHINE_ID 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 /etc/kernel/entry-token, if it exists. Otherwise, a few
       possible candidates below $BOOT 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,
       $KERNEL_INSTALL_MACHINE_ID is used as fallback.

       $KERNEL_INSTALL_BOOT_ROOT 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 $BOOT. Can be overridden by setting $BOOT_ROOT (see below).

       $KERNEL_INSTALL_LAYOUT=auto|bls|uki|other|... is set for the plugins to
       specify the installation layout. Additional layout names may be defined
       by convention. If a plugin uses a special layout, it is encouraged to
       declare its own layout name and configure layout= in install.conf upon
       initial installation. The following values are currently understood:

       bls
	   Standard Boot Loader Specification[2] Type #1 layout, compatible
	   with systemd-boot(7): entries in
	   $BOOT/loader/entries/ENTRY-TOKEN-KERNEL-VERSION[+TRIES].conf,
	   kernel and initrds under $BOOT/ENTRY-TOKEN/KERNEL-VERSION/

	   Implemented by 90-loaderentry.install.

	   Added in version 250.

       uki
	   Standard Boot Loader Specification[2] Type #2 layout, compatible
	   with systemd-boot(7): unified kernel images under $BOOT/EFI/Linux
	   as $BOOT/EFI/Linux/ENTRY-TOKEN-KERNEL-VERSION[+TRIES].efi.

	   Implemented by 90-uki-copy.install.

	   Added in version 253.

       other
	   Some other layout not understood natively by kernel-install.

	   Added in version 250.

       auto
	   Pick the layout automatically. If the kernel is a UKI set layout to
	   uki. If not default to bls if $BOOT/loader/entries.srel with
	   content "type1" or $BOOT/ENTRY-TOKEN exists, or other otherwise.

	   Leaving layout blank has the same effect. This is the default.

	   Added in version 254.

       $KERNEL_INSTALL_INITRD_GENERATOR and $KERNEL_INSTALL_UKI_GENERATOR are
       set for plugins to select the initrd and/or UKI generator. This may be
       configured as initrd_generator= and uki_generator= in install.conf, see
       below.

       $KERNEL_INSTALL_STAGING_AREA 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: Files named initrd* will be installed as INITRD-FILEs, and
       files named microcode* will be prepended before INITRD-FILEs.

   Environment variables understood by kernel-install
       $KERNEL_INSTALL_CONF_ROOT can be set to override the location of the
       configuration files read by kernel-install. When set, install.conf,
       entry-token, and other files will be read from this directory only.
       Note that this path is relative to the host, and in particular symlinks
       in this directory are resolved relative to the host, even if
       --root=root is used. This means that it is generally not correct to use
       this variable to specify a directory underneath root if symlinks are
       used there.

       $KERNEL_INSTALL_PLUGINS can be set to override the list of plugins
       executed by kernel-install. The argument is a whitespace-separated list
       of paths.  "KERNEL_INSTALL_PLUGINS=:" may be used to prevent any
       plugins from running.

       $MACHINE_ID can be set for kernel-install to override
       $KERNEL_INSTALL_MACHINE_ID, the machine ID.

       $BOOT_ROOT can be set for kernel-install to override
       $KERNEL_INSTALL_BOOT_ROOT, the installation location for boot entries.

       The last two variables may also be set in install.conf. Variables set
       in the environment take precedence over the values specified in the
       config file.

EXIT STATUS
       If every executable returns 0 or 77, 0 is returned, and a non-zero
       failure code otherwise.

FILES
       /etc/kernel/install.d/*.install, /usr/lib/kernel/install.d/*.install
	   Drop-in files which are executed by kernel-install.

	   Added in version 198.

       /etc/kernel/cmdline, /usr/lib/kernel/cmdline, /proc/cmdline
	   Specifies the kernel command line to use. The first of the files
	   that is found will be used.	$KERNEL_INSTALL_CONF_ROOT may be used
	   to override the search path; see below for details.

	   Added in version 198.

       /etc/kernel/devicetree, /usr/lib/kernel/devicetree
	   Specifies the partial path to the file containing the device tree
	   blob to install with the kernel and use at boot. The first of the
	   files that is found will be used.  $KERNEL_INSTALL_CONF_ROOT may be
	   used to override the search path; see below for details.

	   The devicetree file contains a path, and this path specifies a
	   location relative to the kernel install tree. A set of locations is
	   checked, including in particular
	   /usr/lib/modules/KERNEL_VERSION/dtb/, which is the recommended
	   location to place the dtb files under. For example, with
	   "broadcom/bcm2711-rpi-4-b.dtb" in the devicetree file, the device
	   tree blob for the Raspberry Pi 4 Model B would be installed, and
	   the actual file would be
	   /usr/lib/modules/KERNEL_VERSION/dtb/broadcom/bcm2711-rpi-4-b.dtb.

	   Added in version 255.

       /etc/kernel/tries
	   Read by 90-loaderentry.install and 90-uki-copy.install. If this
	   file exists, a numeric value is read from it and the naming of the
	   generated entry file or UKI is altered to include it as
	   $BOOT/loader/entries/ENTRY-TOKEN-KERNEL-VERSION+TRIES.conf or
	   $BOOT/EFI/Linux/ENTRY-TOKEN-KERNEL-VERSION+TRIES.efi, respectively.
	   This is useful for boot loaders such as systemd-boot(7) which
	   implement boot attempt counting with a counter embedded in the
	   entry file name.  $KERNEL_INSTALL_CONF_ROOT may be used to override
	   the search path; see below for details.

	   Added in version 240.

       /etc/kernel/entry-token
	   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 $KERNEL_INSTALL_ENTRY_TOKEN above for details.
	   $KERNEL_INSTALL_CONF_ROOT may be used to override the search path;
	   see below for details.

	   Added in version 251.

       /etc/machine-id
	   The content of this file specifies the machine identification
	   MACHINE-ID.

	   Added in version 198.

       /etc/os-release, /usr/lib/os-release
	   Read by 90-loaderentry.install. If available, PRETTY_NAME= is read
	   from these files and used as the title of the boot menu entry.
	   Otherwise, "Linux KERNEL-VERSION" will be used.

	   Added in version 198.

       /etc/kernel/install.conf, /run/kernel/install.conf,
       /usr/local/lib/kernel/install.conf, /usr/lib/kernel/install.conf,
       /etc/kernel/install.conf.d/*.conf, /run/kernel/install.conf.d/*.conf,
       /usr/local/lib/kernel/install.conf.d/*.conf,
       /usr/lib/kernel/install.conf.d/*.conf
	   Configuration file with options for kernel-install, as a series of
	   KEY=VALUE assignments, compatible with shell syntax, following the
	   same rules as described in os-release(5). The first of the files
	   that is found will be used.	$KERNEL_INSTALL_CONF_ROOT may be used
	   to override the search path; see below for details. Drop-in files
	   may also be used to extend the configuration with overrides, see
	   systemd.unit(5).

	   Currently, the following keys are supported: MACHINE_ID=,
	   BOOT_ROOT=, layout=, initrd_generator=, uki_generator=. See the
	   Environment variables section above for details.

	   Added in version 250.

       /etc/kernel/uki.conf
	   Ini-style configuration file for ukify(1) which is only effective
	   when $KERNEL_INSTALL_LAYOUT or layout= in install.conf is set to
	   uki and $KERNEL_INSTALL_UKI_GENERATOR or uki_generator= in
	   install.conf is set to ukify, or is unset.
	   $KERNEL_INSTALL_CONF_ROOT may be used to override the search path;
	   see below for details.

	   Added in version 255.

       /usr/lib/modules/KERNEL-VERSION/
	   Location for installed kernel modules and other kernel related
	   resources. For each locally installed kernel a directory named
	   after the kernel version (uname -r) is kept.

	   Added in version 255.

       /usr/lib/modules/KERNEL-VERSION/vmlinuz
	   Location for installed kernel images. This is the recommended
	   location for OS package managers to install kernel images into (as
	   applicable), from which kernel-install add then copies it into the
	   final boot partition.

	   Added in version 255.

       For various cases listed above, if the $KERNEL_INSTALL_CONF_ROOT
       environment variable is set, it will override the search path. The
       files will be loaded only from the directory specified by the
       environment variable. When the variable is not set, the listed paths
       are tried in turn, and the first file that exists is used.

SEE ALSO
       machine-id(5), os-release(5), depmod(8), systemd-boot(7), ukify(1),
       Boot Loader Specification[2]

NOTES
	1. Nowadays actually CPIO archives used as an "initramfs", rather than
	   "initrd". See bootup(7) for an explanation.

	2. Boot Loader Specification
	   https://uapi-
	   group.org/specifications/specs/boot_loader_specification

	3. Discoverable Partitions Specification
	   https://uapi-
	   group.org/specifications/specs/discoverable_partitions_specification

systemd 258						     KERNEL-INSTALL(8)