BTRFS full disk encryption on Ubuntu 24.04

• With Ubuntu 24.04 it's not longer possible to setup FDE with BTRFS
• The new installer won't offer you any options for manually created dm-crypt volumes
• They move to a TPM-backed solution with a GRUB snap package Show archive.org snapshot
• Alternatives are LVM and encryption on ext4 or ZFS with encryption (experimental)
• Another alternative is a proper Linux distribution Show archive.org snapshot

Caution

Only continue if you're a real BTRFS ultra fan.

Manual BTRFS setup

1. Boot Ubuntu 24.04 Desktop
2. Go to Disk setup -> Erase disk and install Ubuntu -> Advanced features
3. Pick Use LVM and encryption
4. It will setup such a layout

   Copynvme0n1                     259:0    0 931.5G  0 disk  
   ├─nvme0n1p1                 259:1    0     1G  0 part  /boot/efi
   ├─nvme0n1p2                 259:2    0     2G  0 part  /boot
   └─nvme0n1p3                 259:3    0 928.5G  0 part  
     └─dm_crypt-0              252:0    0 928.4G  0 crypt 
       └─ubuntu--vg-ubuntu--lv 252:1    0 928.4G  0 lvm   /
   

5. Reboot
6. Install BTRFS tools: apt install btrfs-progs
7. Set filesystem type to auto: sed -i 's/ext4/auto/g' /etc/fstab
8. Disable the swap file: sed /i 's|^/swap|#&|g' /etc/fstab
9. Create new initrd: update-initramfs -c -k all
10. Reboot to validate everything is still working
11. Boot from Live USB again
12. Unlock the encrypted LVM device
13. Convert the partition to BTRFS: btrfs-convert --uuid copy /dev/mapper/ubuntu--vg-ubuntu--lv
14. Enjoy your new Ubuntu 24.04 with BTRFS

Setup BTRFS subvolumes

1. Boot from Live USB
2. Mount your BTRFS volume: mount -o subvol=/ /dev/mapper/ubuntu--vg-ubuntu--lv /mnt
3. Move default subvolume to @

   Copycd /mnt
   btrfs subvolume snapshot . @
   rmdir @/ext2_saved
   ls | grep -Ev "@|ext2_saved" | xargs rm -rf
   btrfs subvolume set-default @
   

4. Create additional subvolumes

   Copybtrfs subvolume create @home
   cp -ax --reflink=always @/home/* @home
   

5. Add to /etc/fstab:

   Copy/dev/mapper/ubuntu--vg-ubuntu--lv  /home  btrfs defaults,subvol=@home  0 2
   

6. Remove original files after successful migration
7. Repeat for additional subvolumes. Some suggestions:
   • @home
   • @snapshots
   • @swap
   • @tmp
   • @var_tmp
   • @var_snap_lxd
   • @var_lib_docker

Setup swap file

1. btrfs filesystem mkswapfile --size 8g --uuid clear /swap/swapfile
2. Add to /etc/fstab:

   Copy/swap/swapfile none swap defaults 0 0
   

3. Activate with swapon -a
4. Delete old swap file: rm /swap.img