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NAME | SYNOPSIS | DESCRIPTION | COMMANDS | THE $BOOT PARTITION | OPTIONS | ENVIRONMENT VARIABLES | EXIT STATUS | FILES | SEE ALSO | NOTES | COLOPHON |
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KERNEL-INSTALL(8) kernel-install KERNEL-INSTALL(8)
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-IMAGE]
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:
add KERNEL-VERSION KERNEL-IMAGE [INITRD-FILE ...]
This command expects a kernel version string and a path to a
kernel image file as arguments. Optionally, one or more
initrd images may be specified as well (note that plugins
might generate additional ones). kernel-install calls the
executable files from /usr/lib/kernel/install.d/*.install and
/etc/kernel/install.d/*.install (i.e. the plugins) 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.
Two default plugins execute the following operations in this
case:
• kernel-install creates $BOOT/ENTRY-TOKEN/KERNEL-VERSION,
if enabled (see $KERNEL_INSTALL_LAYOUT).
• 50-depmod.install runs depmod(8) for the KERNEL-VERSION.
• 90-loaderentry.install 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 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.
remove KERNEL-VERSION
This command expects a kernel version string as single
argument. This calls executables from
/usr/lib/kernel/install.d/*.install and
/etc/kernel/install.d/*.install 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.
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.
inspect [KERNEL-IMAGE]
Shows the various paths and parameters configured or
auto-detected. In particular shows the values of the various
$KERNEL_INSTALL_* environment variables listed below.
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.
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".
--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.
-h, --help
Print a short help text and exit.
--version
Print a short version string and exit.
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_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:
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.
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.
other
Some other layout not understood natively by kernel-install.
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.
$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.
$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.
/usr/lib/kernel/install.d/*.install
/etc/kernel/install.d/*.install
Drop-in files which are executed by kernel-install.
/usr/lib/kernel/cmdline /etc/kernel/cmdline /proc/cmdline
Read by 90-loaderentry.install. The content of the file
/etc/kernel/cmdline specifies the kernel command line to use.
If that file does not exist, /usr/lib/kernel/cmdline is used.
If that also does not exist, /proc/cmdline is used.
$KERNEL_INSTALL_CONF_ROOT may be used to override the path.
/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 slightly 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 path.
/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 path.
/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 KERNEL-VERSION" will be used.
/usr/lib/kernel/install.conf /etc/kernel/install.conf
Configuration 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).
/etc/kernel/install.conf will be read if present, and
/usr/lib/kernel/install.conf otherwise. This file is
optional. $KERNEL_INSTALL_CONF_ROOT may be used to override
the path.
Currently, the following keys are supported: MACHINE_ID=,
BOOT_ROOT=, layout=, initrd_generator=, uki_generator=. See
the Environment variables section above for details.
machine-id(5), os-release(5), depmod(8), systemd-boot(7), Boot
Loader Specification[2]
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
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have
a bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2023-06-23. (At that
time, the date of the most recent commit that was found in the
repository was 2023-06-23.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
systemd 253 KERNEL-INSTALL(8)
Pages that refer to this page: systemd-firstboot(1), systemd.directives(7), systemd.index(7)
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HTML rendering created 2023-06-24 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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