Raspberry Pi + Archlinux ARM + btrfs

Yes, this is just another post about raspberry pi. However, other instructions seemed over-complicated to me, so I decided to make this small instruction.

But why not default ext4?

Because btrfs can detect data corruption, it has zero-cost atomic snapshots and compression. But as another option you can use F2FS, anyway there is nothing worse than ext4 on SD card.

Step 1

Follow the instructions from https://archlinuxarm.org for your device, however make a btrfs root system (not ext4) (compression & subvolume supported). Don’t forget to mount your subvolumes (/home, /var/log, whatever you created)!

Step 2

Edit etc/fstab, add root entry and other subvolumes. This is my fstab, for example:

# <file system> <dir> <type> <options> <dump> <pass>
/dev/mmcblk1p1  /boot       vfat    defaults  0 0
/dev/mmcblk1p2  /           btrfs   rw,noatime,ssd_spread,space_cache=v2,subvol=@root,compress-force=zstd:3 0 0
/dev/mmcblk1p2  /home       btrfs   rw,noatime,ssd_spread,space_cache=v2,subvol=@home,compress-force=zstd:3 0 0
/dev/mmcblk1p2  /var/log    btrfs   rw,noatime,ssd_spread,space_cache=v2,subvol=@var_log,compress-force=zstd:3 0 0
/dev/mmcblk1p2  /.swap      btrfs   rw,noatime,ssd_spread,space_cache=v2,subvol=@swap 0 0
/.swap/swapfile none        swap    defaults 0 0

Step 3

Add rootflags=subvol=@root to boot/boot.txt. You can probably edit root=PARTUUID=... kernel parameter to boot from usb, but i never tested it.

Step 4

Install uboot tools on your PC (pacman -S uboot-tools on ArchLinux) and run ./mksrc (in boot directory)

That’s all. Now you can boot your raspberry pi and enjoy btrfs features.

UPD

In the same way I was able to move root partition to hdd + bcache + btrfs raid1. Just added bcache to initcpio hooks (between block and filesystems) & modules and changed bootargs to root=UUID=<bcache UUID>. Also changed fstab