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.
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.
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
This is a string denoting the target onto which to install the bootloader.
The interpretation depends on the bootloader in question. For
grub-bootloader, for example, it should be a device name understood by
installer command, such as
(hd0) (see Invoking grub-install in GNU GRUB Manual). For
grub-efi-bootloader, it should be the mount point of the EFI file
system, usually /boot/efi.
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).
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.
For now only GRUB has theme support. GRUB themes are created using
grub-theme form, which is not documented yet.
This is 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.