Zfs: Inappropriate error with 'zfs diff' if filesystem is not mounted

Created on 20 Apr 2015 · 5Comments · Source: openzfs/zfs

Version: at least 0.6.4 affected

If you execute 'zfs diff' between 2 snapshots of a filesystem-dataset, but the dataset is not mounted, you get:

Cannot diff an unmounted snapshot: operation not applicable to datasets of this type

1) It does not matter/help if the snapshot(s) are mounted. It only matters whether the FS is mounted.
2) The operation is certainly applicable to datasets of this type.

After mounting the filesystem, 'zfs diff' operates correctly.

good first issue

Source

jvsalo

Most helpful comment

Same on 0.8.3 .

# zfs create tank/test
# zfs get mountpoint tank/test
NAME       PROPERTY    VALUE       SOURCE
tank/test  mountpoint  none        inherited from tank
# zfs snapshot tank/test@1
# zfs snapshot tank/test@2
# zfs diff tank/test@1 tank/test@2
Cannot diff an unmounted snapshot: operation not applicable to datasets of this type

AceSlash on 8 Apr 2020

😕2 👍2

All 5 comments

Close as stale.

If it's actual - feel free to reopen.

gmelikov on 16 Jul 2017

Still present in 0.8.0-rc3. Getting exactly the same error under the same circumstances as in OP.

lostdj on 3 Feb 2019

The same here.

tomposmiko on 21 Apr 2019

Same on 0.8.3 .

# zfs create tank/test
# zfs get mountpoint tank/test
NAME       PROPERTY    VALUE       SOURCE
tank/test  mountpoint  none        inherited from tank
# zfs snapshot tank/test@1
# zfs snapshot tank/test@2
# zfs diff tank/test@1 tank/test@2
Cannot diff an unmounted snapshot: operation not applicable to datasets of this type

AceSlash on 8 Apr 2020

😕2 👍2

I just hit this with 0.8.4, and it was sufficiently confusing as to make me search for an explanation for that error message. I first tried mounting both snapshots, and that didn't solve the problem.

The error message is confusing, it should state that the operation would succeed if the dataset were mounted.