path: root/upstream/debian-bookworm/man8/kernel-install.8

'\" t
.TH "KERNEL\-INSTALL" "8" "" "systemd 254" "kernel-install"
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.SH "NAME"
kernel-install \- Add and remove kernel and initrd images to and from /boot
.SH "SYNOPSIS"
.HP \w'\fBkernel\-install\fR\ 'u
\fBkernel\-install\fR [OPTIONS...] add \fIKERNEL\-VERSION\fR \fIKERNEL\-IMAGE\fR [\fIINITRD\-FILE\fR...]
.HP \w'\fBkernel\-install\fR\ 'u
\fBkernel\-install\fR [OPTIONS...] remove \fIKERNEL\-VERSION\fR
.HP \w'\fBkernel\-install\fR\ 'u
\fBkernel\-install\fR [OPTIONS...] inspect [\fIKERNEL\-IMAGE\fR]
.SH "DESCRIPTION"
.PP
\fBkernel\-install\fR
is used to install and remove kernel and initrd images
\&\s-2\u[1]\d\s+2
to and from the boot loader partition, referred to as
\fI$BOOT\fR
here\&. It will usually be one of
/boot/,
/efi/, or
/boot/efi/, see below\&.
.PP
\fBkernel\-install\fR
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\&.
.PP
An executable placed in these directories should return
\fB0\fR
on success\&. It may also return
\fB77\fR
to cause the whole operation to terminate (executables later in lexical order will be skipped)\&.
.SH "COMMANDS"
.PP
The following commands are understood:
.PP
\fBadd \fR\fB\fIKERNEL\-VERSION\fR\fR\fB \fR\fB\fIKERNEL\-IMAGE\fR\fR\fB [\fR\fB\fIINITRD\-FILE\fR\fR\fB \&.\&.\&.]\fR
.RS 4
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)\&.
\fBkernel\-install\fR
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:
.sp
.if n \{\
.RS 4
.\}
.nf
add \fIKERNEL\-VERSION\fR $BOOT/\fIENTRY\-TOKEN\fR/\fIKERNEL\-VERSION\fR/ \fIKERNEL\-IMAGE\fR [\fIINITRD\-FILE\fR \&.\&.\&.]
.fi
.if n \{\
.RE
.\}
.sp
The third argument directly refers to the path where to place kernel images, initrd images and other resources for
\m[blue]\fBBoot Loader Specification\fR\m[]\&\s-2\u[2]\d\s+2
Type #1 entries (the "entry directory")\&. If other boot loader schemes are used the parameter may be ignored\&. The
\fIENTRY\-TOKEN\fR
string is typically the machine ID and is supposed to identify the local installation on the system\&. For details see below\&.
.sp
Two default plugins execute the following operations in this case:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
\fBkernel\-install\fR
creates
$BOOT/\fIENTRY\-TOKEN\fR/\fIKERNEL\-VERSION\fR, if enabled (see
\fI$KERNEL_INSTALL_LAYOUT\fR)\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
50\-depmod\&.install
runs
\fBdepmod\fR(8)
for the
\fIKERNEL\-VERSION\fR\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
90\-loaderentry\&.install
copies
\fIKERNEL\-IMAGE\fR
to
$BOOT/\fIENTRY\-TOKEN\fR/\fIKERNEL\-VERSION\fR/linux\&. If
\fIINITRD\-FILE\fRs are provided, it also copies them to
$BOOT/\fIENTRY\-TOKEN\fR/\fIKERNEL_VERSION\fR/\fIINITRD\-FILE\fR\&. This can also be used to prepend microcode before the actual initrd\&. It also creates a boot loader entry according to the
\m[blue]\fBBoot Loader Specification\fR\m[]\&\s-2\u[2]\d\s+2
(Type #1) in
$BOOT/loader/entries/\fIENTRY\-TOKEN\fR\-\fIKERNEL\-VERSION\fR\&.conf\&. The title of the entry is the
\fIPRETTY_NAME\fR
parameter specified in
/etc/os\-release
or
/usr/lib/os\-release
(if the former is missing), or "Linux
\fIKERNEL\-VERSION\fR", if unset\&.
.sp
If
\fI$KERNEL_INSTALL_LAYOUT\fR
is not "bls", this plugin does nothing\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
90\-uki\-copy\&.install
copies a file
uki\&.efi
from
\fI$KERNEL_INSTALL_STAGING_AREA\fR
or if it does not exist the
\fIKERNEL\-IMAGE\fR
argument, only if it has a
"\&.efi"
extension, to
$BOOT/EFI/Linux/\fIENTRY\-TOKEN\fR\-\fIKERNEL\-VERSION\fR\&.efi\&.
.sp
If
\fI$KERNEL_INSTALL_LAYOUT\fR
is not "uki", this plugin does nothing\&.
.RE
.RE
.PP
\fBremove \fR\fB\fIKERNEL\-VERSION\fR\fR
.RS 4
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:
.sp
.if n \{\
.RS 4
.\}
.nf
remove \fIKERNEL\-VERSION\fR $BOOT/\fIENTRY\-TOKEN\fR/\fIKERNEL\-VERSION\fR/
.fi
.if n \{\
.RE
.\}
.sp
Afterwards,
\fBkernel\-install\fR
removes the entry directory
$BOOT/\fIENTRY\-TOKEN\fR/\fIKERNEL\-VERSION\fR/
and its contents, if it exists\&.
.sp
Two default plugins execute the following operations in this case:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
50\-depmod\&.install
removes the files generated by
\fBdepmod\fR
for this kernel again\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
90\-loaderentry\&.install
removes the file
$BOOT/loader/entries/\fIENTRY\-TOKEN\fR\-\fIKERNEL\-VERSION\fR\&.conf\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
90\-uki\-copy\&.install
removes the file
$BOOT/EFI/Linux/\fIENTRY\-TOKEN\fR\-\fIKERNEL\-VERSION\fR\&.efi\&.
.RE
.RE
.PP
\fBinspect [\fR\fB\fIKERNEL\-IMAGE\fR\fR\fB]\fR
.RS 4
Shows the various paths and parameters configured or auto\-detected\&. In particular shows the values of the various
\fI$KERNEL_INSTALL_*\fR
environment variables listed below\&.
.RE
.SH "THE \FI$BOOT\FR PARTITION"
.PP
The partition where the kernels and
\m[blue]\fBBoot Loader Specification\fR\m[]\&\s-2\u[2]\d\s+2
snippets are located is called
\fI$BOOT\fR\&.
\fBkernel\-install\fR
determines the location of this partition by checking
/efi/,
/boot/, and
/boot/efi/
in turn\&. The first location where
$BOOT/loader/entries/
or
$BOOT/\fIENTRY\-TOKEN\fR/
exists is used\&.
.SH "OPTIONS"
.PP
The following options are understood:
.PP
\fB\-\-esp\-path=\fR
.RS 4
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\&.
.RE
.PP
\fB\-\-boot\-path=\fR
.RS 4
Path to the Extended Boot Loader partition, as defined in the
\m[blue]\fBBoot Loader Specification\fR\m[]\&\s-2\u[2]\d\s+2\&. If not specified,
/boot/
is checked\&. It is recommended to mount the Extended Boot Loader partition to
/boot/, if possible\&.
.RE
.PP
\fB\-\-make\-entry\-directory=yes|no|auto\fR
.RS 4
Controls creation and deletion of the
\m[blue]\fBBoot Loader Specification\fR\m[]\&\s-2\u[2]\d\s+2
Type #1 entry directory on the file system containing resources such as kernel and initrd images during
\fBadd\fR
and
\fBremove\fR, 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"\&.
.RE
.PP
\fB\-\-entry\-token=\fR
.RS 4
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\&.
.sp
If set to
\fBmachine\-id\fR
the entries are named after the machine ID of the running system (e\&.g\&.
"b0e793a9baf14b5fa13ecbe84ff637ac")\&. See
\fBmachine-id\fR(5)
for details about the machine ID concept and file\&.
.sp
If set to
\fBos\-id\fR
the entries are named after the OS ID of the running system, i\&.e\&. the
\fIID=\fR
field of
\fBos-release\fR(5)
(e\&.g\&.
"fedora")\&. Similarly, if set to
\fBos\-image\-id\fR
the entries are named after the OS image ID of the running system, i\&.e\&. the
\fIIMAGE_ID=\fR
field of
os\-release
(e\&.g\&.
"vendorx\-cashier\-system")\&.
.sp
If set to
\fBauto\fR
(the default), the
/etc/kernel/entry\-token
(or
$KERNEL_INSTALL_CONF_ROOT/entry\-token) file will be read if it exists, and the stored value used\&. Otherwise if the local machine ID is initialized it is used\&. Otherwise
\fIIMAGE_ID=\fR
from
os\-release
will be used, if set\&. Otherwise,
\fIID=\fR
from
os\-release
will be used, if set\&. Otherwise a randomly generated machine ID is used\&.
.sp
Using the machine ID for naming the entries is generally preferable, however there are cases where using the other identifiers is a good option\&. Specifically: if the identification data that the machine ID entails shall not be stored on the (unencrypted)
\fI$BOOT_ROOT\fR
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\&.
.RE
.PP
\fB\-v\fR, \fB\-\-verbose\fR
.RS 4
Output additional information about operations being performed\&.
.RE
.PP
\fB\-h\fR, \fB\-\-help\fR
.RS 4
Print a short help text and exit\&.
.RE
.PP
\fB\-\-version\fR
.RS 4
Print a short version string and exit\&.
.RE
.SH "ENVIRONMENT VARIABLES"
.SS "Environment variables exported for plugins"
.PP
If
\fB\-\-verbose\fR
is used,
\fI$KERNEL_INSTALL_VERBOSE=1\fR
will be exported for plugins\&. They may output additional logs in this case\&.
.PP
\fI$KERNEL_INSTALL_IMAGE_TYPE=uki|pe|unknown\fR
is set for the plugins to specify the type of the kernel image\&.
.PP
uki
.RS 4
Unified kernel image\&.
.RE
.PP
pe
.RS 4
PE binary\&.
.RE
.PP
unknown
.RS 4
Unknown type\&.
.RE
.PP
\fI$KERNEL_INSTALL_MACHINE_ID\fR
is set for the plugins to the desired machine\-id to use\&. It\*(Aqs always a 128\-bit ID\&. Normally it\*(Aqs read from
/etc/machine\-id, but it can also be overridden via
\fI$MACHINE_ID\fR
(see below)\&. If not specified via these methods, a fallback value will generated by
\fBkernel\-install\fR
and used only for a single invocation\&.
.PP
\fI$KERNEL_INSTALL_ENTRY_TOKEN\fR
is set for the plugins to the desired entry "token" to use\&. It\*(Aqs an identifier that shall be used to identify the local installation, and is often the machine ID, i\&.e\&. same as
\fI$KERNEL_INSTALL_MACHINE_ID\fR, but might also be a different type of identifier, for example a fixed string or the
\fIID=\fR,
\fIIMAGE_ID=\fR
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\&.
.PP
Note that while
\fI$KERNEL_INSTALL_ENTRY_TOKEN\fR
and
\fI$KERNEL_INSTALL_MACHINE_ID\fR
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
\fI$BOOT\fR
are checked for Boot Loader Specification Type 1 entry directories, and if found the entry token is derived from that\&. If that is not successful,
\fI$KERNEL_INSTALL_MACHINE_ID\fR
is used as fallback\&.
.PP
\fI$KERNEL_INSTALL_BOOT_ROOT\fR
is set for the plugins to the absolute path of the root directory (mount point, usually) of the hierarchy where boot loader entries, kernel images, and associated resources should be placed\&. This usually is the path where the XBOOTLDR partition or the ESP (EFI System Partition) are mounted, and also conceptually referred to as
\fI$BOOT\fR\&. Can be overridden by setting
\fI$BOOT_ROOT\fR
(see below)\&.
.PP
\fI$KERNEL_INSTALL_LAYOUT=auto|bls|uki|other|\&.\&.\&.\fR
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\*(Aqs encouraged to declare its own layout name and configure
\fIlayout=\fR
in
install\&.conf
upon initial installation\&. The following values are currently understood:
.PP
bls
.RS 4
Standard
\m[blue]\fBBoot Loader Specification\fR\m[]\&\s-2\u[2]\d\s+2
Type #1 layout, compatible with
\fBsystemd-boot\fR(7): entries in
$BOOT/loader/entries/\fIENTRY\-TOKEN\fR\-\fIKERNEL\-VERSION\fR[+\fITRIES\fR]\&.conf, kernel and initrds under
$BOOT/\fIENTRY\-TOKEN\fR/\fIKERNEL\-VERSION\fR/
.sp
Implemented by
90\-loaderentry\&.install\&.
.RE
.PP
uki
.RS 4
Standard
\m[blue]\fBBoot Loader Specification\fR\m[]\&\s-2\u[2]\d\s+2
Type #2 layout, compatible with
\fBsystemd-boot\fR(7): unified kernel images under
$BOOT/EFI/Linux
as
$BOOT/EFI/Linux/\fIENTRY\-TOKEN\fR\-\fIKERNEL\-VERSION\fR[+\fITRIES\fR]\&.efi\&.
.sp
Implemented by
90\-uki\-copy\&.install\&.
.RE
.PP
other
.RS 4
Some other layout not understood natively by
\fBkernel\-install\fR\&.
.RE
.PP
auto
.RS 4
Pick the layout automatically\&. If the kernel is a UKI set layout to
\fBuki\fR\&. If not default to
\fBbls\fR
if
$BOOT/loader/entries\&.srel
with content
"type1"
or
$BOOT/\fIENTRY\-TOKEN\fR
exists, or
\fBother\fR
otherwise\&.
.sp
Leaving layout blank has the same effect\&. This is the default\&.
.RE
.PP
\fI$KERNEL_INSTALL_INITRD_GENERATOR\fR
and
\fI$KERNEL_INSTALL_UKI_GENERATOR\fR
are set for plugins to select the initrd and/or UKI generator\&. This may be configured as
\fIinitrd_generator=\fR
and
\fIuki_generator=\fR
in
install\&.conf, see below\&.
.PP
\fI$KERNEL_INSTALL_STAGING_AREA\fR
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
\fIINITRD\-FILE\fRs, and files named
microcode*
will be prepended before
\fIINITRD\-FILE\fRs\&.
.SS "Environment variables understood by kernel\-install"
.PP
\fI$KERNEL_INSTALL_CONF_ROOT\fR
can be set to override the location of the configuration files read by
\fBkernel\-install\fR\&. When set,
install\&.conf,
entry\-token, and other files will be read from this directory\&.
.PP
\fI$KERNEL_INSTALL_PLUGINS\fR
can be set to override the list of plugins executed by
\fBkernel\-install\fR\&. The argument is a whitespace\-separated list of paths\&.
"KERNEL_INSTALL_PLUGINS=:"
may be used to prevent any plugins from running\&.
.PP
\fI$MACHINE_ID\fR
can be set for
\fBkernel\-install\fR
to override
\fI$KERNEL_INSTALL_MACHINE_ID\fR, the machine ID\&.
.PP
\fI$BOOT_ROOT\fR
can be set for
\fBkernel\-install\fR
to override
\fI$KERNEL_INSTALL_BOOT_ROOT\fR, the installation location for boot entries\&.
.PP
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\&.
.SH "EXIT STATUS"
.PP
If every executable returns 0 or 77, 0 is returned, and a non\-zero failure code otherwise\&.
.SH "FILES"
.PP
/usr/lib/kernel/install\&.d/*\&.install /etc/kernel/install\&.d/*\&.install
.RS 4
Drop\-in files which are executed by kernel\-install\&.
.RE
.PP
/usr/lib/kernel/cmdline /etc/kernel/cmdline /proc/cmdline
.RS 4
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\&.
\fI$KERNEL_INSTALL_CONF_ROOT\fR
may be used to override the path\&.
.RE
.PP
/etc/kernel/tries
.RS 4
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/\fIENTRY\-TOKEN\fR\-\fIKERNEL\-VERSION\fR+\fITRIES\fR\&.conf
or
$BOOT/EFI/Linux/\fIENTRY\-TOKEN\fR\-\fIKERNEL\-VERSION\fR+\fITRIES\fR\&.efi, respectively\&. This is useful for boot loaders such as
\fBsystemd-boot\fR(7)
which implement boot attempt counting with a counter embedded in the entry file name\&.
\fI$KERNEL_INSTALL_CONF_ROOT\fR
may be used to override the path\&.
.RE
.PP
/etc/kernel/entry\-token
.RS 4
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
\fI$KERNEL_INSTALL_ENTRY_TOKEN\fR
above for details\&.
\fI$KERNEL_INSTALL_CONF_ROOT\fR
may be used to override the path\&.
.RE
.PP
/etc/machine\-id
.RS 4
The content of this file specifies the machine identification
\fIMACHINE\-ID\fR\&.
.RE
.PP
/etc/os\-release /usr/lib/os\-release
.RS 4
Read by
90\-loaderentry\&.install\&. If available,
\fIPRETTY_NAME=\fR
is read from these files and used as the title of the boot menu entry\&. Otherwise,
"Linux \fIKERNEL\-VERSION\fR"
will be used\&.
.RE
.PP
/usr/lib/kernel/install\&.conf /etc/kernel/install\&.conf
.RS 4
Configuration options for
\fBkernel\-install\fR, as a series of
\fIKEY=\fR\fIVALUE\fR
assignments, compatible with shell syntax, following the same rules as described in
\fBos-release\fR(5)\&.
/etc/kernel/install\&.conf
will be read if present, and
/usr/lib/kernel/install\&.conf
otherwise\&. This file is optional\&.
\fI$KERNEL_INSTALL_CONF_ROOT\fR
may be used to override the path\&.
.sp
Currently, the following keys are supported:
\fIMACHINE_ID=\fR,
\fIBOOT_ROOT=\fR,
\fIlayout=\fR,
\fIinitrd_generator=\fR,
\fIuki_generator=\fR\&. See the Environment variables section above for details\&.
.RE
.PP
/etc/kernel/uki\&.conf
.RS 4
Ini\-style configuration file for
\fBukify\fR(1)
which is only effective when
\fI$KERNEL_INSTALL_LAYOUT\fR
or
\fIlayout=\fR
in
install\&.conf
is set to
\fBuki\fR
and
\fI$KERNEL_INSTALL_UKI_GENERATOR\fR
or
\fIuki_generator=\fR
in
install\&.conf
is set to
\fBukify\fR\&.
\fI$KERNEL_INSTALL_CONF_ROOT\fR
may be used to override the path\&.
.RE
.SH "SEE ALSO"
.PP
\fBmachine-id\fR(5),
\fBos-release\fR(5),
\fBdepmod\fR(8),
\fBsystemd-boot\fR(7),
\fBukify\fR(1),
\m[blue]\fBBoot Loader Specification\fR\m[]\&\s-2\u[2]\d\s+2
.SH "NOTES"
.IP " 1." 4
Nowadays actually CPIO archives used as an "initramfs", rather than "initrd". See
\fBbootup\fR(7)
for an explanation.
.IP " 2." 4
Boot Loader Specification
.RS 4
\%https://uapi-group.org/specifications/specs/boot_loader_specification
.RE