Ubuntu 22.04 on encrypted ZFS and wrong crypttab setup

[Bartosz]

I have installed Ubuntu 22.04 with ZFS and its native encryption (using the official installer, Ubiquity, no hacking at all). And everything was working great!

I decided to add a second NVMe drive, to install Windows on it. And I found a weird Windows behavior, because it was crashing, not booting etc.
The next day I found that my SWAP space is HUGE, more than 200 GB, but should be 2 gigs only.

I have started looking at this weird issue:

root@bzieba-desktop:~# swapon --show
NAME TYPE SIZE USED PRIO
/dev/dm-1 partition 238,5G 0B -2

root@bzieba-desktop:~# grep -i swap /etc/fstab
/dev/mapper/cryptoswap none swap sw 0 0

root@bzieba-desktop:~# cat /etc/crypttab
cryptoswap /dev/nvme0n1p2 /dev/urandom swap,initramfsroot@bzieba-desktop:~#

And here is the issue!
nvme0n1p2 was my Ubuntu NVMe, but now, after adding the second NVMe drive, it's a Windows partition.
Ubuntu started overwriting my Windows data (but I don't care, no worries).

===

Ubuntu uses UUIDs for most FS/partitions:
root@bzieba-desktop:~# grep -i uuid /etc/fstab
UUID=2CCE-15F1 /boot/efi vfat umask=0022,fmask=0022,dmask=0022 0 1

root@bzieba-desktop:~# zpool status -v rpool
  pool: rpool
 state: ONLINE
  scan: scrub repaired 0B in 00:00:46 with 0 errors on Sun Jun 12 00:24:49 2022
config:

 NAME STATE READ WRITE CKSUM
 rpool ONLINE 0 0 0
   4633606d-c5e6-3343-a211-9bb5a2d9ad0b ONLINE 0 0 0

So why it doesn't use UUID for /etc/crypttab and cryptswap device?

===

I found that it comes from Ubiquity, scripts/zsys-setup:

printf "${swap_name}\t${orig_swap_device}\t/dev/urandom\tswap,initramfs" >> "${TARGET}/etc/crypttab"

Where:
orig_swap_device="${swap_device}"
swap_device="${DISK}${PARTBASE}${PARTSWAP}"

===

I believe we should fix that and start using PARTUUID for crypttab and cryptswap device because it already exists:

root@bzieba-desktop:~# blkid -s PARTUUID -o value /dev/nvme1n1p2
5373106c-7691-b448-98c6-718c4458979c

root@bzieba-desktop:~# cat /etc/crypttab
cryptoswap PARTUUID=5373106c-7691-b448-98c6-718c4458979c /dev/urandom swap,initramfs

And now SWAP is working on the correct partition:

root@bzieba-desktop:~# swapon --show
NAME TYPE SIZE USED PRIO
/dev/dm-1 partition 2G 0B -2

===

If someone confirm that it needs a fix, I would love to prepare the fix and push it to the repo :)