Bootloaders
By default Alpine uses Syslinux as bootloader. This page shows the basic steps you need to perform, if you for any reason want to switch bootloaders or apply some manual configuration.
Installing Syslinux
If you want to switch from another bootloader back to Syslinux, or if you for some reason want to install Syslinux manually, the following steps are required.
Install the syslinux package:
apk add syslinux
If you're using GPT partitions, install the GPT MBR onto the drive you want to install the bootloader on (in this case /dev/sda):
dd bs=440 count=1 conv=notrunc if=/usr/share/syslinux/gptmbr.bin of=/dev/sda
Or if you're using DOS partitions, install the DOS MBR instead:
dd bs=440 count=1 conv=notrunc if=/usr/share/syslinux/mbr.bin of=/dev/sda
Next install the required Syslinux binaries. Despite being called extlinux, Syslinux supports booting from FAT12/16/32, NTFS, ext2/3/4, Btrfs, XFS, and UFS/FFS filesystems.
extlinux --install /boot
The configuration file is located in /boot/extlinux.conf.
Alpine ships with a script called update-extlinux which automatically (re)generates this file, for example on updates to Syslinux.
The settings for this script can be found in /etc/update-extlinux.conf, including the option to disable automatic overwriting of /boot/extlinux.conf.
You can also place additional menu entries in the /etc/update-extlinux.d/ directory, e.g. for dual booting.
EFI
Assuming /mnt is a FAT32 partition of type EF00 and /boot belongs to the rootfs created after running setup-disk:
mkdir -p /mnt/EFI/syslinux cp /usr/share/syslinux/efi64/* /mnt/EFI/syslinux/ cp /boot/extlinux.conf /mnt/EFI/syslinux/syslinux.cfg cp /boot/vmlinuz* /mnt/ cp /boot/initramfs* /mnt/
You may need to modify /mnt/EFI/syslinux/syslinux.cfg to change the paths to absolute paths (just add a / in front of the vmlinuz/initramfs entries),
or copy the files to /mnt/EFI/syslinux instead (XXX: untested).
GRUB
To install GRUB in BIOS mode, (optionally) remove the Syslinux package and install the required GRUB packages:
apk del syslinux apk add grub grub-bios
For EFI, install Grub's EFI package instead. Note that /boot has to be an EFI compatible filesystem like FAT32.
apk add grub-efi
Next install the MBR and GRUB binaries to disk for BIOS mode:
grub-install /dev/vda
For EFI mode:
grub-install --target=x86_64-efi --efi-directory=/boot
GRUB ships with an automatic config generator, including some automatic detection of other operating systems installed on the device:
grub-mkconfig -o /boot/grub/grub.cfg
This script can be configured via the /etc/default/grub file.
See [1] for a list of available options.
systemd-boot
Systemd-boot is the simple EFI bootloader part of the systemd project. It is also available in the Alpine Linux testing repository as a standalone component.
Installing
To install the systemd-boot, enable the testing repository, and install the systemd-boot package. Then make sure the boot and EFI partitions are mounted as read-write and install the bootloader with bootctl.
# apk add systemd-boot # bootctl install
The bootctl binary also has support for checking if the bootloader is installed.
# bootctl is-installed yes
Configuring
Example configuration files for alpine are available on /usr/share/systemd/bootctl as loader.conf and alpine.conf.
The bootloader (not the boot entries) can be configured via the loader.conf file, an example is available in /usr/share/systemd/bootctl/loader.conf.
# cp /usr/share/systemd/bootctl/loader.conf /boot/loader # vi /boot/loader/loader.conf
systemd-boot makes use of configuration files in /boot/loader/entries to list entries for different OSes it can boot into. An example file for Alpine Linux is present on /usr/share/systemd/bootctl/alpine.conf.
# cp /usr/share/systemd/bootctl/alpine.conf /boot/loader/entries # vi /boot/loader/entries/alpine.conf
The example file has a skeleton structure that requires minimal modifications to make them work. You need to modify the example file to fit your oeprating system, among them:
- Replace root=UUID=XXXX with the UUID of the root partition.
- Replace rootfstype with the filesystem used for the root filesystem.
- Add boot options required/recommended for booting your operating system (E.g: cryptdm=, cryptroot=, modules=, etc).
- (If you don't use the default linux-lts kernel) Replace vmlinuz-lts and initramfs-lts with the ones that are used.
- (If you use an Intel CPU and need Intel microcode) add
initrd /intel-ucode.imgbefore the initrd call for the initramfs
All the options available are documented in the systemd boot loader specification under Technical Details.
Updating
When the systemd-boot package is updated then the bootloader installed needs to be updated as well:
# bootctl update
Removing
If for any reason you wish to not use systemd-boot anymore then the bootctl binary also provides a command for easily removing the files that were installed with the install command:
# bootctl remove # apk del systemd-boot