Uninstall ZFS installed via Ubuntu 20.04 installer

Question

Apologies if this has been answered somewhere, I've searched everywhere and couldn't find anything.

I'm a PhD student and I manage a small cluster for our group. When installing Ubuntu 20.04 on our servers we chose the "experimental" zfs feature. We've run into a few issues over the last two years and we never used ZFS to our advantage. We upgraded to Ubuntu 22.04 we'd like to uninstall it now - but can we?

When I run zpool list I see bpool and rpool - so if I uninstalled the packages (not suer which ones since I didn't explicitly install them), would the system even boot? Clearly I don't know much about ZFS and shouldn't have installed it..

Obviously I would really like to avoid re-installing everything because it takes a really long time and things generally break. Thanks in advance!

Edit: Here's the requested output (although it sounds like I'm SOL).

$ sudo df -h
Filesystem                                        Size  Used Avail Use% Mounted on
tmpfs                                             6.3G  2.9M  6.3G   1% /run
rpool/ROOT/ubuntu_3tmtm1                          830G   25G  805G   3% /
tmpfs                                              32G   16K   32G   1% /dev/shm
tmpfs                                             5.0M     0  5.0M   0% /run/lock
rpool/ROOT/ubuntu_3tmtm1/var/www                  805G  128K  805G   1% /var/www
rpool/ROOT/ubuntu_3tmtm1/var/snap                 805G  3.9M  805G   1% /var/snap
rpool/ROOT/ubuntu_3tmtm1/var/games                805G  128K  805G   1% /var/games
rpool/ROOT/ubuntu_3tmtm1/srv                      805G  128K  805G   1% /srv
rpool/ROOT/ubuntu_3tmtm1/usr/local                841G   36G  805G   5% /usr/local
rpool/ROOT/ubuntu_3tmtm1/var/spool                805G  256K  805G   1% /var/spool
rpool/ROOT/ubuntu_3tmtm1/var/lib                  809G  4.1G  805G   1% /var/lib
rpool/ROOT/ubuntu_3tmtm1/var/mail                 805G  128K  805G   1% /var/mail
rpool/ROOT/ubuntu_3tmtm1/var/log                  805G  154M  805G   1% /var/log
rpool/ROOT/ubuntu_3tmtm1/var/lib/NetworkManager   805G  256K  805G   1% /var/lib/NetworkManager
rpool/ROOT/ubuntu_3tmtm1/var/lib/AccountsService  805G  128K  805G   1% /var/lib/AccountsService
rpool/ROOT/ubuntu_3tmtm1/var/lib/apt              806G  522M  805G   1% /var/lib/apt
rpool/ROOT/ubuntu_3tmtm1/var/lib/dpkg             805G   76M  805G   1% /var/lib/dpkg
bpool/BOOT/ubuntu_3tmtm1                          1.8G  253M  1.6G  15% /boot
/dev/sda1                                         511M  7.1M  504M   2% /boot/efi
169.237.79.48:/mnt/home                           8.0T  1.7T  6.3T  22% /home
169.237.79.48:/mnt/data                            11T  7.8T  3.0T  73% /data
169.237.79.48:/mnt/backup                          12T   28G   12T   1% /backup
169.237.79.48:/mnt/nvme                           5.1T  3.8T  1.4T  74% /nvme

$ sudo df -hT
Filesystem                                       Type   Size  Used Avail Use% Mounted on
tmpfs                                            tmpfs  6.3G  2.9M  6.3G   1% /run
rpool/ROOT/ubuntu_3tmtm1                         zfs    830G   25G  805G   3% /
tmpfs                                            tmpfs   32G   16K   32G   1% /dev/shm
tmpfs                                            tmpfs  5.0M     0  5.0M   0% /run/lock
rpool/ROOT/ubuntu_3tmtm1/var/www                 zfs    805G  128K  805G   1% /var/www
rpool/ROOT/ubuntu_3tmtm1/var/snap                zfs    805G  3.9M  805G   1% /var/snap
rpool/ROOT/ubuntu_3tmtm1/var/games               zfs    805G  128K  805G   1% /var/games
rpool/ROOT/ubuntu_3tmtm1/srv                     zfs    805G  128K  805G   1% /srv
rpool/ROOT/ubuntu_3tmtm1/usr/local               zfs    841G   36G  805G   5% /usr/local
rpool/ROOT/ubuntu_3tmtm1/var/spool               zfs    805G  256K  805G   1% /var/spool
rpool/ROOT/ubuntu_3tmtm1/var/lib                 zfs    809G  4.1G  805G   1% /var/lib
rpool/ROOT/ubuntu_3tmtm1/var/mail                zfs    805G  128K  805G   1% /var/mail
rpool/ROOT/ubuntu_3tmtm1/var/log                 zfs    805G  154M  805G   1% /var/log
rpool/ROOT/ubuntu_3tmtm1/var/lib/NetworkManager  zfs    805G  256K  805G   1% /var/lib/NetworkManager
rpool/ROOT/ubuntu_3tmtm1/var/lib/AccountsService zfs    805G  128K  805G   1% /var/lib/AccountsService
rpool/ROOT/ubuntu_3tmtm1/var/lib/apt             zfs    806G  522M  805G   1% /var/lib/apt
rpool/ROOT/ubuntu_3tmtm1/var/lib/dpkg            zfs    805G   76M  805G   1% /var/lib/dpkg
bpool/BOOT/ubuntu_3tmtm1                         zfs    1.8G  253M  1.6G  15% /boot
/dev/sda1                                        vfat   511M  7.1M  504M   2% /boot/efi
169.237.79.48:/mnt/home                          nfs    8.0T  1.7T  6.3T  22% /home
169.237.79.48:/mnt/data                          nfs     11T  7.8T  3.0T  73% /data
169.237.79.48:/mnt/backup                        nfs     12T   28G   12T   1% /backup
169.237.79.48:/mnt/nvme                          nfs    5.1T  3.8T  1.4T  74% /nvme

$ sudo lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
loop0    7:0    0     4K  1 loop /snap/bare/5
loop1    7:1    0  55.6M  1 loop /snap/core18/2714
loop2    7:2    0  55.6M  1 loop /snap/core18/2721
loop3    7:3    0    73M  1 loop /snap/core22/607
loop4    7:4    0  63.3M  1 loop /snap/core20/1828
loop5    7:5    0 349.7M  1 loop /snap/gnome-3-38-2004/137
loop6    7:6    0 346.3M  1 loop /snap/gnome-3-38-2004/119
loop7    7:7    0  63.3M  1 loop /snap/core20/1852
loop8    7:8    0 460.4M  1 loop /snap/gnome-42-2204/68
loop9    7:9    0  53.2M  1 loop /snap/snapd/18933
loop10   7:10   0  81.3M  1 loop /snap/gtk-common-themes/1534
loop11   7:11   0  45.9M  1 loop /snap/snap-store/638
loop12   7:12   0  45.9M  1 loop /snap/snap-store/599
loop13   7:13   0  91.7M  1 loop /snap/gtk-common-themes/1535
loop14   7:14   0  49.8M  1 loop /snap/snapd/18596
loop16   7:16   0   428K  1 loop /snap/snapd-desktop-integration/57
loop17   7:17   0 241.9M  1 loop /snap/firefox/2559
loop18   7:18   0 460.6M  1 loop /snap/gnome-42-2204/87
loop19   7:19   0 241.9M  1 loop /snap/firefox/2579
sda      8:0    0 931.5G  0 disk 
├─sda1   8:1    0   512M  0 part /boot/grub
│                                /boot/efi
├─sda2   8:2    0     1K  0 part 
├─sda5   8:5    0     2G  0 part [SWAP]
├─sda6   8:6    0     2G  0 part 
└─sda7   8:7    0   927G  0 part
 
$ sudo zpool status
  pool: bpool
 state: ONLINE
  scan: scrub repaired 0B in 00:00:03 with 0 errors on Sun Apr  9 00:24:04 2023
config:

        NAME           STATE     READ WRITE CKSUM
        bpool          ONLINE       0     0     0
          214bb022-06  ONLINE       0     0     0

errors: No known data errors

  pool: rpool
 state: ONLINE
status: Some supported and requested features are not enabled on the pool.
        The pool can still be used, but some features are unavailable.
action: Enable all features using 'zpool upgrade'. Once this is done,
        the pool may no longer be accessible by software that does not support
        the features. See zpool-features(7) for details.
  scan: scrub repaired 0B in 00:29:07 with 0 errors on Sun Apr  9 00:53:13 2023
config:

        NAME           STATE     READ WRITE CKSUM
        rpool          ONLINE       0     0     0
          214bb022-07  ONLINE       0     0     0

errors: No known data errors

Hello. Your a PhD student? don't worry, noobody is perfect :p. (sorry private joke). Before uninstalling zfs (and pools) and breaking your data, may you provide the following output? (it will help to understand your config): df -h, df -hT, lsblk, zpool status, thanks. — petitradisgris, Apr 10 '23 at 19:04
If ZFS was chosen during install, your rootfs is likely ZFS formatted so removing associated packages would be a bad idea and the only way to "fix" it would be to reinstall. The commands indicated by petitradisgris should help confirm whether or not that's the case. — Ginnungagap, Apr 10 '23 at 19:35

score 1 · Accepted Answer · answered Apr 10 '23 at 20:24

1

The "experimental" tag is for Ubuntu ZFS-on-root setup, not for ZFS-based data disks. In other words, you installed the OS itself (ie: Ubuntu) on ZFS. As such, you can't really uninstall ZFS - otherwise, the OS will not boot. You have to reinstall your system to get rid of ZFS.

answered Apr 10 '23 at 20:24

shodanshok

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Thank you, this is what I kind of thought.. – Collin McCarthy Apr 22 '23 at 00:45

Uninstall ZFS installed via Ubuntu 20.04 installer

1 Answers1