The operating system supports multiple bootloaders. The bootloader is
bootloader-configuration declaration. All the
fields of this structure are bootloader agnostic except for one field,
bootloader that indicates the bootloader to be configured and
Some of the bootloaders do not honor every field of
bootloader-configuration. For instance, the extlinux
bootloader does not support themes and thus ignores the
The type of a bootloader configuration declaration.
The bootloader to use, as a
bootloader object. For now
u-boot-bootloader are supported.
Available bootloaders are described in
(gnu bootloader …)
modules. In particular,
(gnu bootloader u-boot) contains definitions
of bootloaders for a wide range of ARM and AArch64 systems, using the
grub-efi-bootloader allows to boot on modern systems using the
Unified Extensible Firmware Interface (UEFI). This is what you should
use if the installation image contains a /sys/firmware/efi directory
when you boot it on your system.
grub-bootloader allows you to boot in particular Intel-based machines
in “legacy” BIOS mode.
grub-efi-netboot-bootloader allows you to boot your system over network
through TFTP. In combination with an NFS root file system this allows you to
build a diskless Guix system.
The installation of the
grub-efi-netboot-bootloader generates the
content of the TFTP root directory at
targets), to be served by a TFTP server. You may
want to mount your TFTP server directories onto the
move the required files to the TFTP server automatically.
If you plan to use an NFS root file system as well (actually if you mount the
store from an NFS share), then the TFTP server needs to serve the file
/boot/grub/grub.cfg and other files from the store (like GRUBs background
image, the kernel (see
kernel) and the
initrd)), too. All these
files from the store will be accessed by GRUB through TFTP with their normal
store path, for example as
Two symlinks are created to make this possible. For each target in the
targets field, the first symlink is
‘target’/efi/Guix/boot/grub/grub.cfg pointing to
../../../boot/grub/grub.cfg, where ‘target’ may be
/boot. In this case the link is not leaving the served TFTP root
directory, but otherwise it does. The second link is
‘target’/gnu/store and points to ../gnu/store. This
link is leaving the served TFTP root directory.
The assumption behind all this is that you have an NFS server exporting
the root file system for your Guix system, and additionally a TFTP
server exporting your
targets directories—usually a single
/boot—from that same root file system for your Guix system. In
this constellation the symlinks will work.
For other constellations you will have to program your own bootloader
installer, which then takes care to make necessary files from the store
accessible through TFTP, for example by copying them into the TFTP root
directory to your
It is important to note that symlinks pointing outside the TFTP root directory may need to be allowed in the configuration of your TFTP server. Further the store link exposes the whole store through TFTP. Both points need to be considered carefully for security aspects.
grub-efi-netboot-bootloader, the already mentioned TFTP and
NFS servers, you also need a properly configured DHCP server to make the booting
over netboot possible. For all this we can currently only recommend you to look
for instructions about PXE (Preboot eXecution Environment).
grub-efi-removable-bootloader allows you to boot your system from
removable media by writing the GRUB file to the UEFI-specification location of
/EFI/BOOT/BOOTX64.efi of the boot directory, usually /boot/efi.
This is also useful for some UEFI firmwares that “forget” their configuration
from their non-volatile storage. Like
grub-efi-bootloader, this can only
be used if the /sys/firmware/efi directory is available.
Note: This will overwrite the GRUB file from any other operating systems that also place their GRUB file in the UEFI-specification location; making them unbootable.
This is a list of strings denoting the targets onto which to install the bootloader.
The interpretation of targets depends on the bootloader in question.
grub-bootloader, for example, they should be device names
understood by the bootloader
installer command, such as
(hd0) (see Invoking grub-install in GNU GRUB Manual). For
grub-efi-removable-bootloader they should be mount
points of the EFI file system, usually /boot/efi. For
targets should be the mount
points corresponding to TFTP root directories served by your TFTP
A possibly empty list of
menu-entry objects (see below), denoting
entries to appear in the bootloader menu, in addition to the current
system entry and the entry pointing to previous system generations.
The index of the default boot menu entry. Index 0 is for the entry of the current system.
The number of seconds to wait for keyboard input before booting. Set to 0 to boot immediately, and to -1 to wait indefinitely.
If this is
#f, the bootloader’s menu (if any) uses the default keyboard
layout, usually US English (“qwerty”).
Otherwise, this must be a
keyboard-layout object (see Keyboard Layout).
Note: This option is currently ignored by bootloaders other than
The bootloader theme object describing the theme to use. If no theme is provided, some bootloaders might use a default theme, that’s true for GRUB.
The output terminals used for the bootloader boot menu, as a list of
symbols. GRUB accepts the values:
pkmodem. This field
corresponds to the GRUB variable
GRUB_TERMINAL_OUTPUT (see Simple
configuration in GNU GRUB manual).
The input terminals used for the bootloader boot menu, as a list of
symbols. For GRUB, the default is the native platform terminal as
determined at run-time. GRUB accepts the values:
usb_keyboard. This field corresponds to the GRUB variable
GRUB_TERMINAL_INPUT (see Simple configuration in GNU GRUB
The serial unit used by the bootloader, as an integer from 0 to 3. For GRUB, it is chosen at run-time; currently GRUB chooses 0, which corresponds to COM1 (see Serial terminal in GNU GRUB manual).
The speed of the serial interface, as an integer. For GRUB, the default value is chosen at run-time; currently GRUB chooses 9600 bps (see Serial terminal in GNU GRUB manual).
Whether to support Linux device tree files loading.
This option in enabled by default. In some cases involving the
u-boot bootloader, where the device tree has already been loaded
in RAM, it can be handy to disable the option by setting it to
Should you want to list additional boot menu entries via the
menu-entries field above, you will need to create them with the
menu-entry form. For example, imagine you want to be able to
boot another distro (hard to imagine!), you can define a menu entry
along these lines:
(menu-entry (label "The Other Distro") (linux "/boot/old/vmlinux-2.6.32") (linux-arguments '("root=/dev/sda2")) (initrd "/boot/old/initrd"))
The type of an entry in the bootloader menu.
The label to show in the menu—e.g.,
The Linux kernel image to boot, for example:
(file-append linux-libre "/bzImage")
For GRUB, it is also possible to specify a device explicitly in the file path using GRUB’s device naming convention (see Naming convention in GNU GRUB manual), for example:
If the device is specified explicitly as above, then the
field is ignored entirely.
The list of extra Linux kernel command-line arguments—e.g.,
A G-Expression or string denoting the file name of the initial RAM disk to use (see G-Expressions).
The device where the kernel and initrd are to be found—i.e., for GRUB, root for this menu entry (see root in GNU GRUB manual).
This may be a file system label (a string), a file system UUID (a
bytevector, see File Systems), or
#f, in which case
the bootloader will search the device containing the file specified by
linux field (see search in GNU GRUB manual). It
must not be an OS device name such as /dev/sda1.
The kernel to boot in Multiboot-mode (see multiboot in GNU GRUB manual). When this field is set, a Multiboot menu-entry is generated. For example:
(file-append mach "/boot/gnumach")
The list of extra command-line arguments for the multiboot-kernel.
The list of commands for loading Multiboot modules. For example:
A string that can be accepted by
directive. This has no effect if either
multiboot-kernel fields are specified. The following is an
example of chainloading a different GNU/Linux system.
For now only GRUB has theme support. GRUB themes are created using
grub-theme form, which is not fully documented yet.
Data type representing the configuration of the GRUB theme.
gfxmode to set (a list of screen resolution strings,
see gfxmode in GNU GRUB manual).
Return the default GRUB theme used by the operating system if no
theme field is specified in
It comes with a fancy background image displaying the GNU and Guix logos.
For example, to override the default resolution, you may use something like
(bootloader (bootloader-configuration ;; … (theme (grub-theme (inherit (grub-theme)) (gfxmode '("1024x786x32" "auto"))))))