ZFS "cannot open [...]: dataset does not exist"

Niklaas Baudet von Gersdorff niklaas at kulturflatrate.net
Mon Dec 8 20:03:18 UTC 2014

Dear Mailinglist,

I am currently using zfssnap.sh [1] to make a regular backup of
the entire ZFS pool on our server. In principal, this works great,
nevertheless, every time I am running the script I get the following

    cannot open 'tank/usr/ports': dataset does not exist
    cannot open 'tank/usr/src': dataset does not exist

    1:  https://bitbucket.org/mmichele/zfssnap

I did some research on the net and I guess this is related to an already
asked question that has never been answered [2], to a bug whose record I
cannot find on the net [3] and a solution I do not completely understand

    2: https://forums.freebsd.org/threads/spurious-zfs-dataset-does-not-exist-errors.19878/

    3: https://lists.freebsd.org/pipermail/freebsd-fs/2010-December/010224.html

    4: https://lists.freebsd.org/pipermail/freebsd-fs/2010-December/010225.html

Please have a look at [4] especially. It seems like there are certain
"state files" still existing. As far as I understand it, these state
files are responsible for ZFS looking for a dataset that actually does
not exist. Unfortunately, I cannot find anything under `/dev/` that I
might be able to delete. (There is `/dev/zfs/` which is not a directory
I can `cd` into.)

In case someone could hint me to these state files or any other tip is
very much appreciated.

    $ zfs list
    NAME                                      USED  AVAIL  REFER  MOUNTPOINT
    tank                                     14.7G  1.68T    31K  none
    tank/jails                               12.8G  1.68T    32K  /usr/local/jails
    tank/jails/ezjails                       12.8G  1.68T    62K  /usr/local/jails/ezjails
    tank/jails/ezjails/basejail              2.41G  1.68T  1.63G  /usr/local/jails/ezjails/basejail
    tank/jails/ezjails/fulljail                31K  1.68T    31K  /usr/local/jails/ezjails/fulljail
    tank/jails/ezjails/[** censored **    ]   577M  1.68T   469M  /usr/local/jails/ezjails/[** censored **    ]
    tank/jails/ezjails/newjail               2.72M  1.68T  1.85M  /usr/local/jails/ezjails/newjail
    tank/jails/ezjails/[** censored **    ]   367M  1.68T   336M  /usr/local/jails/ezjails/[** censored **    ]
    tank/jails/ezjails/[** censored **    ]  9.51G  1.68T  7.85G  /usr/local/jails/ezjails/[** censored **    ]
    tank/root                                1.78G  1.68T   974M  /
    tank/root/tmp                             328K  1.68T    39K  /tmp
    tank/root/var                             660M  1.68T   401M  /var

    $ uname -a
    FreeBSD [** censored **    ] 10.0-RELEASE-p12 FreeBSD 10.0-RELEASE-p12 #0: Tue Nov  4 05:07:17 UTC 2014     root at amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC  amd64

Thank you and best,


Baudet von Gersdorff
niklaas at kulturflatrate.net


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