[SOLVED] Proxmox boot error: zfs-import-scan finds phantom pool

[n_pacheco]

Hi everyone,

during the boot process of my Proxmox node I noticed repeated errors related to zfs-import-scan. Looking at the logs, it seems the system is still detecting an old ZFS pool that should have been destroyed long ago:

Aug 10 09:42:11 pve zpool[1187]: cannot import 'app': pool was previously in use from another system.
Aug 10 09:42:11 pve zpool[1187]: Last accessed by truenas (hostid=34ab91e2) at Mon Jan  1 00:00:00 1970
Aug 10 09:42:11 pve zpool[1187]: The pool can be imported, use 'zpool import -f' to import the pool.

For context, I had been running a TrueNAS VM, and the pool named app was attached to it. That VM has since been deleted, so the pool should no longer exist.

When I test manually, I see this:

root@pve:~# zpool import -f
no pools available to import

root@pve:~# zpool import -afN -d /dev/disk/by-id -o cachefile=none
internal error: cannot import 'app': Value too large for defined data type
Aborted

Could someone advise me on how to really remove this ghost pool so that zfs-import-scan stops complaining?

Thanks a lot in advance for any hints!

 

[pcarone]

Hello,


this situation usually happens when ZFS finds leftover labels on a disk or volume that was once part of a pool. Even if the VM is gone, those metadata remain and zfs-import-scan will keep trying to import them.


The way to confirm is by checking the device directly:

root@pve:~# zdb -l /dev/nvme0n1
failed to unpack label 0
failed to unpack label 1
------------------------------------
LABEL 2 (Bad label cksum)
------------------------------------
    version: 5000
    name: 'app'
    state: 0
    txg: 4
    pool_guid: 15398451237812093475
    hostid: 892374615
    hostname: 'truenas'
    ...
    labels = 2 3

As you can see, the device still carries the pool metadata for app.
The fix is to clear those ZFS labels manually with:

root@pve:~# zpool labelclear -f /dev/nvme0n1

After doing this, the boot messages should disappear and zfs-import-scan will no longer try to import the phantom pool.


Best regards, and glad to help!