Install Alpine on a btrfs filesystem with refind as boot manager

It is assumed that your other OS is already installed and working with rEFInd as boot manager. Currently it is  part of  Testing repository.

Boot your PC from the Alpine Linux USB. Once booted, log in as root (no password required). Identify your partitions by using the command.

# blkid

/dev/nvme0n1p1: UUID="55C3-8AB4" TYPE="vfat"
/dev/nvme0n1p2: UUID="dab64e31-fb89-4364-b90f-b79400f73304" TYPE="swap"
/dev/nvme0n1p3: LABEL="BTRFSVOL" UUID="823a3283-30a7-4fef-b50b-8a2230c71b5b" TYPE="btrfs"

Mount the btrfs partition to /mnt

# mount /dev/nvme0n1p3 /mnt -t btrfs

Run the setup script:

# setup-alpine

This will guide you through basic system configuration. Follow the prompts to:

Select keyboard layout
Set hostname
Configure network (choose your WiFi interface and enter your WiFi credentials)
Set root password
Choose timezone
Choose NTP client (chronyd)
Choose a mirror for packages
Create a new user (optional but recommended)
After this accept the remaining choices.

Once basic setup is complete, prepare your disk for installation: Create a new Btrfs subvolume for Alpine and you need btrfs-progs package

# apk add btrfs-progs

Create a new Btrfs subvolume for Alpine:

# btrfs subvolume create /mnt/@alpine

# umount /mnt

Mount the new subvolume and other necessary partitions:

# mount /dev/nvme0n1p3 /mnt -t btrfs

# mkdir /mnt/os

# mount -o subvol=@alpine /dev/nvme0n1p3 /mnt/os

Install the base system using the below command:

# setup-disk -m sys /mnt/os

This will install the base system to the mounted subvolume. Once the base system is installed, chroot into the new system:

# chroot /mnt/os

Edit /etc/fstab to use the correct subvolume. Ensure the root entry looks like this:

/dev/nvme0n1p3 / btrfs subvol=@alpine,rw,relatime 0 1

Also verify linux kernel and firmware are installed successfully.

# apk list --installed

If your other OS is already installed and working with refind as boot manager, then there is no need to install refind here. You may want to remove the grub and grub-efi packages

# apk del grub grub-efi

Exit the chroot:

# exit

Mount the EFI partition to edit the refind.conf file

# mkdir /mnt/os/boot/efi

# mount dev/nvme0n1p1 /mnt/os/boot/efi

Edit /mnt/os/boot/efi/EFI/refind/refind.conf to boot alpine:

Add an entry for Alpine:

menuentry "Alpine Linux" {

   volume   "BTRFSVOL"
   loader   @alpine/boot/vmlinuz-lts
   initrd   @alpine/boot/initramfs-lts
   options  "root=UUID=823a3283-30a7-4fef-b50b-8a2230c71b5b rw rootflags=subvol=@alpine rootfstype=btrfs"
   # PARTUUID not working for alpine unlike arch

}

Save and exit the editor.

Unmount everything:

# umount -R /mnt

Reboot your system.

# reboot

Now, you should now see an option to boot into Alpine Linux in the rEFInd boot menu.