kernel-install — Add and remove kernel and initramfs images to and from /boot
kernel-install COMMAND [OPTIONS...]
kernel-install is used to install and remove kernel and initramfs images to and
from the boot loader partition, referred to as
$BOOT here. It will usually be one of
/boot/efi/, see below.
kernel-install will run the executable files ("plugins") located in the
/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
An executable placed in these directories should return
0 on success. It may
77 to cause the whole operation to terminate (executables later in
lexical order will be skipped).
The following commands are understood:
This command expects a kernel version string and a path to a kernel image file as
arguments. Optionally, one or more initial RAM disk images may be specified as well (note that
plugins might generate additional ones). kernel-install calls the executable
/etc/kernel/install.d/*.install (i.e. the plugins) with the following
The third argument directly refers to the path where to place kernel images, initial RAM disk
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:
if enabled (see
depmod(8) for the
INITRD-FILEs are provided, it also copies them to
It also creates a boot loader entry according to the Boot Loader Specification (Type #1) in
The title of the entry is the
PRETTY_NAME parameter specified in
/usr/lib/os-release (if the former
is missing), or "Linux
KERNEL-VERSION", if unset.
$KERNEL_INSTALL_LAYOUT is not "bls", this plugin does nothing.
This command expects a kernel version string as single argument. This calls executables from
/etc/kernel/install.d/*.install with the following arguments:
Afterwards, kernel-install removes the entry directory
and its contents, if it exists.
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
Shows the various paths and parameters configured or auto-detected. In particular shows the
values of the various
$KERNEL_INSTALL_* environment variables listed
The partition where the kernels and Boot
Loader Specification snippets are located is called
kernel-install determines the location of this partition by checking
/boot/efi/ in turn. The
first location where
$BOOT/ exists is used.
The following options are understood:
--verbose is used,
$KERNEL_INSTALL_VERBOSE=1 will be set for
the plugins. They may output additional logs in this case.
$MACHINE_ID is set and not empty when kernel-install is
invoked, it will be used as
MACHINE-ID, overriding any automatic detection
attempts. The value must be a valid machine ID (32 hexadecimal characters).
$KERNEL_INSTALL_MACHINE_ID is set for the plugins to the desired
MACHINE-ID to use. It's always a 128bit ID, and typically the ID from
/etc/machine-id or the one passed in via
$MACHINE_ID. (If no
machine ID was specified via these methods it might be generated randomly by
kernel-install, in which case it only applies to this 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
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 oftentimes
$KERNEL_INSTALL_MACHINE_ID are 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 the
$BOOT are searched for Boot Loader Specification Type 1 entry directories, and if
found the entry token is derived from that. If that is not successful the machine ID is used as
$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
$KERNEL_INSTALL_LAYOUT=bls|other|... is set for the plugins to specify the
installation layout. Defaults to
$BOOT/ exists, or
otherwise. 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
install.conf upon initial installation. The following values are currently
Standard Boot Loader
Specification Type #1 layout, compatible with
kernel and initrds under
Some other layout not understood natively by kernel-install.
$KERNEL_INSTALL_INITRD_GENERATOR is set for plugins to select the initrd
generator. This may be configured as
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.
If every executable returns 0 or 77, 0 is returned, and a non-zero failure code otherwise.
Drop-in files which are executed by kernel-install.
90-loaderentry.install. The content of the file
/etc/kernel/cmdline specifies the kernel command line to use. If that file does not
/usr/lib/kernel/cmdline is used. If that also does not exist,
/proc/cmdline is used.
90-loaderentry.install. If this file exists a numeric value is read from
it and the naming of the generated entry file is slightly altered to include it as
is useful for boot loaders such as
implement boot attempt counting with a counter embedded in the entry file name.
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.
The content of this file specifies the machine identification
PRETTY_NAME= is read from these files and used as the title of the boot menu entry.
Linux " will be used.
Configuration options for kernel-install, as a series of
VALUE assignments, compatible with shell
syntax. This currently supports two keys:
initrd_generator=, for details see the Environment variables section above.