nullfs making contents of ZFS datasets invisible even after unmounting

tsuroerusu at gmail.com tsuroerusu at gmail.com
Mon Aug 14 08:34:06 UTC 2017


I am running a FreeBSD 11.1 system with ZFS and jails and I mount a
file system on my storage pool (/storage/cloud) into the jail
(/jails/cloud/storage) via nullfs, and that works fine for what the
jail does. However I just noticed that outside the jail, I can only
see the mount points of the file system children, but not the
contents.

For example if I do: ls -la /storage/cloud/* (As root) then nothing
shows up, but they are present inside the jail. Even if I stop the
jail, they still are not present outside the jail.

I just tried disabling jails in /etc/rc.conf and rebooting the system
and EVEN THEN the files do not reappear outside the jail in their
original location, yet zfs list reports the space being used. But if I
then (without rebooting) enable the jail, the files show up in the
nullfs-mounted location inside the jail!

As an experiment, I tried creating /mnt/test and /mnt/test2 and
creates a folder and a few files in test, and then nullfs-mounted it
onto test2, and I could then see the files in both locations.

Does anybody know what might be causing this? The fact that my data
stays hidden after a reboot is rather worrisome.


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