kernel-install — Add and remove kernel and initrd images to and from /boot
kernel-install [OPTIONS...] add KERNEL-VERSION KERNEL-IMAGE [INITRD-FILE...]
kernel-install [OPTIONS...] remove KERNEL-VERSION
kernel-install [OPTIONS...] inspect [KERNEL-VERSION] [KERNEL-IMAGE] [INITRD-FILE...]
kernel-install [OPTIONS...] list
kernel-install is used to install and remove kernel and initrd images
[1]
to and from the boot loader partition, referred to as $BOOT here. It will usually be
one of /boot/, /efi/, or /boot/efi/, see
below.
kernel-install will run the executable files ("plugins") located in the
directory /usr/lib/kernel/install.d/ and the local administration directory
/etc/kernel/install.d/. All files are collectively sorted and executed in lexical
order, regardless of the directory in which they live. However, files with identical filenames replace
each other. Files in /etc/kernel/install.d/ take precedence over files with the
same name in /usr/lib/kernel/install.d/. This can be used to override a
system-supplied executables with a local file if needed; a symbolic link in
/etc/kernel/install.d/ with the same name as an executable in
/usr/lib/kernel/install.d/, pointing to /dev/null, disables the
executable entirely. Executables must have the extension ".install"; other extensions
are ignored.
An executable placed in these directories should return 0 on success. It may
also return 77 to cause the whole operation to terminate (executables later in
lexical order will be skipped).
The following commands are understood:
KERNEL-VERSION] KERNEL-IMAGE] [INITRD-FILE ...]]
¶This command takes a kernel version string and a path to a kernel image file as arguments. If
the former is omitted, specified as an empty string or as "-" it defaults to the current kernel
version, i.e. the same string uname -r returns. If the latter is omitted,
specified as an empty string or as "-" defaults to
/usr/lib/modules/. Optionally,
one or more initrd images may be specified as well (note that plugins might generate additional
ones).KERNEL_VERSION/vmlinuz
The executable files from /usr/lib/kernel/install.d/*.install and
/etc/kernel/install.d/*.install (i.e. the plugins) are called with the
following arguments:
addKERNEL-VERSION$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 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.
Two default plugins execute the following operations in this case:
kernel-install creates
$BOOT/,
if enabled (see ENTRY-TOKEN/KERNEL-VERSION$KERNEL_INSTALL_LAYOUT).
50-depmod.install runs
depmod(8) for the
KERNEL-VERSION.
90-loaderentry.install copies
KERNEL-IMAGE to
$BOOT/.
If ENTRY-TOKEN/KERNEL-VERSION/linuxINITRD-FILEs are provided, it also copies them to
$BOOT/.
This can also be used to prepend microcode before the actual initrd. It also creates a boot loader entry according to the Boot Loader Specification (Type #1) in
ENTRY-TOKEN/KERNEL_VERSION/INITRD-FILE$BOOT/loader/entries/.
The title of the entry is the ENTRY-TOKEN-KERNEL-VERSION.confPRETTY_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 copies a file
uki.efi from $KERNEL_INSTALL_STAGING_AREA or if it does
not exist the KERNEL-IMAGE argument, only if it has a
".efi" extension, to
$BOOT/EFI/Linux/.ENTRY-TOKEN-KERNEL-VERSION.efi
If $KERNEL_INSTALL_LAYOUT is not "uki", this plugin does nothing.
This is the same as add (see above), but invokes the operation iteratively
for every installed kernel in /usr/lib/modules/. This operation is only
supported on systems where the kernel image is installed in
/usr/lib/modules/.KERNEL-VERSION/vmlinuz
KERNEL-VERSION¶This command expects a kernel version string as single argument.
The executable files from /usr/lib/kernel/install.d/*.install and
/etc/kernel/install.d/*.install (i.e. the plugins) are called with the
following arguments:
removeKERNEL-VERSION$BOOT/ENTRY-TOKEN/KERNEL-VERSION/
Afterwards, kernel-install removes the entry directory
$BOOT/
and its contents, if it exists.ENTRY-TOKEN/KERNEL-VERSION/
Two default plugins execute the following operations in this case:
50-depmod.install removes the files generated by
depmod for this kernel again.
90-loaderentry.install removes the file
$BOOT/loader/entries/.
ENTRY-TOKEN-KERNEL-VERSION.conf
90-uki-copy.install removes the file
$BOOT/EFI/Linux/.
ENTRY-TOKEN-KERNEL-VERSION.efi
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.
Shows the various installed kernels. This enumerates the subdirectories of
/usr/lib/modules/, and shows whether a kernel image is installed there.
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.
$BOOT partition¶The partition where the kernels and Boot
Loader Specification 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/ exists is used.ENTRY-TOKEN/
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.
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
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".
--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.
-v, --verbose¶Output additional information about operations being performed.
--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.
--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. For further information on supported disk images, see
systemd-nspawn(1)'s
switch of the same name.
-h, --help¶--version¶--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.
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.
$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's 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's encouraged to declare its own layout name and configure layout= in
install.conf upon initial installation. The following values are currently
understood:
Standard Boot Loader
Specification Type #1 layout, compatible with
systemd-boot(7):
entries in
$BOOT/loader/entries/,
kernel and initrds under
ENTRY-TOKEN-KERNEL-VERSION[+TRIES].conf$BOOT/ENTRY-TOKEN/KERNEL-VERSION/
Implemented by 90-loaderentry.install.
Standard Boot Loader
Specification 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.
Some other layout not understood natively by kernel-install.
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/ exists, or
ENTRY-TOKENother otherwise.
Leaving layout blank has the same effect. This is the default.
$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.
$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.
$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.
If every executable returns 0 or 77, 0 is returned, and a non-zero failure code otherwise.
/etc/kernel/install.d/*.install, /usr/lib/kernel/install.d/*.install¶Drop-in files which are executed by kernel-install.
/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.
/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/, which is the
recommended location to place the dtb files under. For example, with
"KERNEL_VERSION/dtb/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
/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
$BOOT/loader/entries/
or
ENTRY-TOKEN-KERNEL-VERSION+TRIES.conf$BOOT/EFI/Linux/,
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.
ENTRY-TOKEN-KERNEL-VERSION+TRIES.efi$KERNEL_INSTALL_CONF_ROOT may be used to override the search path; see below for
details.
/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.
/etc/machine-id
¶The content of this file specifies the machine identification
MACHINE-ID.
/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 " will be
used.KERNEL-VERSION
/etc/kernel/install.conf, /usr/lib/kernel/install.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.
Currently, the following keys are supported:
MACHINE_ID=,
BOOT_ROOT=,
layout=,
initrd_generator=,
uki_generator=.
See the Environment variables section above for details.
/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.
/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.
/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.
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.