freebsd stable - May 2017 - zpool imported twice with different names (was Re: Fwd: ZFS)

On Mon, 15 May 2017 20:11+0200, Nikos Vassiliadis wrote:
> Fix the e-mail subject
> 
> On 05/15/2017 08:09 PM, Nikos Vassiliadis wrote:
> > Hi everybody,
> > 
> > While trying to rename a zpool from zroot to vega,
> > I ended up in this strange situation:
> > nik at vega:~ % zfs list -t all
> > NAME                 USED  AVAIL  REFER  MOUNTPOINT
> > vega                1.83G  34.7G    96K  /zroot
> > vega/ROOT           1.24G  34.7G    96K  none
> > vega/ROOT/default   1.24G  34.7G  1.24G  /
> > vega/tmp             120K  34.7G   120K  /tmp
> > vega/usr             608M  34.7G    96K  /usr
> > vega/usr/home        136K  34.7G   136K  /usr/home
> > vega/usr/ports        96K  34.7G    96K  /usr/ports
> > vega/usr/src         607M  34.7G   607M  /usr/src
> > vega/var             720K  34.7G    96K  /var
> > vega/var/audit        96K  34.7G    96K  /var/audit
> > vega/var/crash        96K  34.7G    96K  /var/crash
> > vega/var/log         236K  34.7G   236K  /var/log
> > vega/var/mail        100K  34.7G   100K  /var/mail
> > vega/var/tmp          96K  34.7G    96K  /var/tmp
> > zroot               1.83G  34.7G    96K  /zroot
> > zroot/ROOT          1.24G  34.7G    96K  none
> > zroot/ROOT/default  1.24G  34.7G  1.24G  /
> > zroot/tmp            120K  34.7G   120K  /tmp
> > zroot/usr            608M  34.7G    96K  /usr
> > zroot/usr/home       136K  34.7G   136K  /usr/home
> > zroot/usr/ports       96K  34.7G    96K  /usr/ports
> > zroot/usr/src        607M  34.7G   607M  /usr/src
> > zroot/var            724K  34.7G    96K  /var
> > zroot/var/audit       96K  34.7G    96K  /var/audit
> > zroot/var/crash       96K  34.7G    96K  /var/crash
> > zroot/var/log        240K  34.7G   240K  /var/log
> > zroot/var/mail       100K  34.7G   100K  /var/mail
> > zroot/var/tmp         96K  34.7G    96K  /var/tmp
> > nik at vega:~ % zpool status
> >    pool: vega
> >   state: ONLINE
> >    scan: scrub repaired 0 in 0h0m with 0 errors on Mon May 15 01:28:48
2017
> > config:
> > 
> >      NAME        STATE     READ WRITE CKSUM
> >      vega        ONLINE       0     0     0
> >        vtbd0p3   ONLINE       0     0     0
> > 
> > errors: No known data errors
> > 
> >    pool: zroot
> >   state: ONLINE
> >    scan: scrub repaired 0 in 0h0m with 0 errors on Mon May 15 01:28:48
2017
> > config:
> > 
> >      NAME        STATE     READ WRITE CKSUM
> >      zroot       ONLINE       0     0     0
> >        vtbd0p3   ONLINE       0     0     0
> > 
> > errors: No known data errors
> > nik at vega:~ %
> > -------------------------------------------
> > 
> > It seems like there are two pools, sharing the same vdev...
> > 
> > After running a few commands in this state, like doing a scrub,
> > the pool was (most probably) destroyed. It couldn't boot anymore
> > and I didn't research further. Is this a known bug?
> > 
I guess you had a /boot/zfs/zpool.cache file referring to the original 
zroot pool. Next, the kernel found the vega pool and didn't realise 
these two pools are the very same.
> > Steps to reproduce:
> >    install FreeBSD-11.0 in a pool named zroot
> >    reboot into a live-CD
Redo the above steps.
> >    zpool import -f zroot vega
Do these four commands instead of a regular import:

mkdir /tmp/vega
zpool import -N -f -o cachefile=/tmp/zpool.cache vega
mount -t zfs vega/ROOT/default /tmp/vega
cp -p /tmp/zpool.cache /tmp/vega/boot/zfs/zpool.cache
> >    reboot again
Reboot again.
> > 
> > Thanks,
> > Nikos
> > 
> > PS:
> > Sorry for the cross-posting, I am doing this to share to more people
> > because it is a rather easy way to destroy a ZFS pool.
-- 
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| Vennlig hilsen,               | Best regards,                      |
| Trond Endrest?l,              | Trond Endrest?l,                   |
| IT-ansvarlig,                 | System administrator,              |
| Fagskolen Innlandet,          | Gj?vik Technical College, Norway,  |
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On Tue, May 16, 2017 at 1:31 AM, Trond Endrest?l <
Trond.Endrestol at fagskolen.gjovik.no> wrote:
> I guess you had a /boot/zfs/zpool.cache file referring to the original
> zroot pool. Next, the kernel found the vega pool and didn't realise
> these two pools are the very same.
>
Assuming this is the case, shouldn't it be fixed? A check while importing
that the guid of the pool targeted for import is not in the set of
currently active guids would be worthwhile, but it -- apparently, if this
is reproducible -- doesn't exist?

Again, assuming this is reproducible.

 - Eric