Raspberry Pi 4 - Ubuntu 20.04 w/Btrfs root

Apr 23, 2021 · 283 words · 2 minute read

How to convert a root file system on a Raspberry Pi 4 b running Ubuntu 20.04 64 bit to Btrfs in a few simple steps.

Why 🔗

First, why should I care about doing this.

Btrfs is SSD-aware, even on a SD card. The copy on write file system will ensure that your writes will be spread out and decrease wear leveling.
You can enable a CPU friendly compression, zstd, that decreases the amount of data written to your SD card.

How 🔗

Flash Ubuntu on the SD card as usual.
Mount the partitions and go to where the partitions are mounted, example on Fedora.
```
cd /run/media/${USER}
```

Tell boot to read from a Btrfs file system on next boot

sudo sed -i 's/ext4/btrfs/' system-boot/cmdline.txt

Update /etc/fstab with new file system, and ensure minimum writes to SD card.

sudo sed -E -i 's|(.*)ext4.*|\1btrfs compress=zstd:1,noatime,nodiratime 0 0|' writable/etc/fstab

Unmount the file system.

sudo umount system-boot
sudo umount writable

Convert the file system on the SD card. If the SD cards ext4 partition are /dev/sda2 then the command will be as follows. Let the command finish.
```
sudo btrfs-convert -p /dev/sda2
```
Put the SD card in the Raspberry Pi and boot. Voila! You have a Btrfs root file system.
Log into the Raspberry Pi for some cleanup.
Remove the old ext2 backup.
```
sudo btrfs sub del /ext2_saved
```
Defrag and compress already existing OS.
```
sudo btrfs fi def -czstd -r -v /
```

Congratulations! Now you have a Btrfs root file system with compression. Writes will take less space, and wear leveling is down. Note that you also have saved space by running a df -h /. Enjoy a SD card that will last longer than you are used to.

pi btrfs