Limine
Limine is an advanced, portable, multiprotocol boot loader originally developed as the reference implementation for the Limine boot protocol, but also supporting the ability to boot Linux as well as to chainload other boot loaders.
esp denotes the mountpoint of the EFI system partition aka ESP.Supported file systems
Limine supports FAT12, FAT16, FAT32 and ISO9660. Additionally experimental support for ext2 through ext4 is present, albeit with limited upstream support. The list of supported file systems is intentionally limited per Limine's design philosophy.
Installation
Installing the Limine boot loader
BIOS systems
MBR vs. GPT
Legacy PC BIOS is capable of booting from either GPT or MBR partitioned devices. Limine supports both, with a very similar installation procedure. Furthermore, unlike GRUB, it does not require creating an extra partition containing raw data when installing to a GPT partitioned device.
Choosing GPT is beneficial for larger drives as it allows placing partitions further than 2TiB on disk, alongside additional benefits such as partition and disk GUIDs.
On the other hand, MBR is older and more limited, but it will ensure compatibility with quirky BIOSes which refuse to boot from GPT partitioned media.
Deployment
Core bootloader files are in /usr/share/limine/. Most important for installing to BIOS systems is the limine-bios.sys file, which contains stage 3 code that Limine needs to boot. This file needs to reside on either the root, a /boot, a /limine, or a /boot/limine directory of any partition on the disk onto which Limine will be deployed, as long as the filesystem is supported.
For example:
# cp /usr/share/limine/limine-bios.sys /boot/
Then stage 1 and 2 need to be deployed on disk. The installation is identical regardless of whether MBR or GPT is used, as it will auto-detect what scheme is used and install itself appropriately:
# limine bios-install /dev/sdX
where /dev/sdX is the disk (not a partition) where Limine is to be installed. For example /dev/sda or /dev/nvme0n1. See Device file#Block device names for a description of the block device naming scheme.
UEFI systems
Deploying Limine on UEFI systems involves copying the /usr/share/limine/BOOTX64.EFI file to an EFI system partition, usually to esp/EFI/BOOT/BOOTX64.EFI, but it can be given other filenames, as long as the UEFI BIOS is aware of them. Unlike GRUB, Limine does not add an entry for the bootloader in the NVRAM: use efibootmgr to setup an entry for Limine.
UEFI+BIOS bootable drives
As long as a drive is GPT formatted, and it contains an EFI system partition, it is possible to follow both the BIOS and UEFI deployment procedures in order to create a drive capable of booting on both legacy BIOS as well as UEFI systems. This is useful, for example, for installing an operating system on a USB flash drive which is to be used on multiple systems which may, or may not support UEFI, or to ease moving hard drives across systems.
Configuration
limine does not ship a default configuration file, it is therefore necessary to create one. This file is necessary to teach Limine which operating systems are available for boot. The configuration file has a lot of options as Limine allows for a fair degree of customisation. A detailed documentation of the configuration file, its format, and its options can be found here.
The configuration file, just like limine-bios.sys, needs to reside on either the root, a /boot, a /limine, or a /boot/limine directory of a partition on the drive on which Limine is deployed, as long as the file system of said partition is supported. The configuration file has to be named limine.conf.
boot():/ represents the partition on which limine.conf is located. In case there is no separate /boot partition, and limine.conf resides on the root partition instead, then, in the following example, boot():/ should instead be boot():/boot/.Here follows a simple example configuration that contains 1 boot menu entry that describes a typical Arch Linux kernel and initramfs:
limine.conf
timeout: 5
/Arch Linux
protocol: linux
kernel_path: boot():/vmlinuz-linux
kernel_cmdline: root=UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx rw
module_path: boot():/initramfs-linux.img
where xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx is the root file system's UUID.
To prevent this you should first embed the b2sum checksum of every resource file in the configuration. Limine file paths have an optional field containing the b2sum checksum of the file. This field can be specified by appending the # character and then the 128 characters checksum:
boot():/path#checksumTo protect the config file you should embed its
b2sum in the EFI executable with limine enroll-config command.Windows entry
In order to be able to boot windows we need to know the path of bootmgfw.efi in the ESP. This can be done by going inside the ESP and using the following command:
$ find -name "bootmgfw.efi"
./EFI/Microsoft/Boot/bootmgfw.efi
All we need to do now is adding the following to the configuration:
limine.conf
/Windows
protocol: efi_chainload
image_path: boot():/EFI/Microsoft/Boot/bootmgfw.efi
pacman hook
While not mandatory, it may be useful to set up a pacman hook to deploy Limine whenever it is upgraded.
The following are just examples. Edit paths and devices to match the system's configuration.
BIOS
/etc/pacman.d/hooks/liminedeploy.hook
[Trigger] Operation = Install Operation = Upgrade Type = Package Target = limine [Action] Description = Deploying Limine after upgrade... When = PostTransaction Exec = /bin/sh -c "/usr/bin/limine bios-install /dev/sdX && /usr/bin/cp /usr/share/limine/limine-bios.sys /boot/"
UEFI
/etc/pacman.d/hooks/liminedeploy.hook
[Trigger] Operation = Install Operation = Upgrade Type = Package Target = limine [Action] Description = Deploying Limine after upgrade... When = PostTransaction Exec = /usr/bin/cp /usr/share/limine/BOOTX64.EFI /boot/EFI/BOOT/