zpool import -N mounts filesystems anyway

[Mel Pilgrim]

On 06/17/2017 20:59, David Christensen wrote:
> On 06/17/17 17:00, Mel Pilgrim wrote:
>> I need to import a pool without mounting its filesystems, but when I use
>> the -N argument to zpool import to, per the man page, "Import the pool
>> without mounting any file systems", it mounts the filesystems anyway.
>>
>> I've tried search for an answer to this, but the question is too
>> ambiguous to get a decent search result.
>>
>> How do I tell ZFS to not mount anything on import?
> 
> Which version of FreeBSD?

11.0-RELEASE-p7
The pools and filesystems are all at current feature sets and versions.

> My man 8 zpool shows three forms for import:
> 
>       zpool import [-d dir | -c cachefile] [-D]
>       zpool import [-o mntopts] [-o property=value] ... [-d dir | -c 
> cachefile]
>             [-D] [-f] [-m] [-N] [-R root] [-F [-n]] -a
>       zpool import [-o mntopts] [-o property=value] ... [-d dir | -c 
> cachefile]
>             [-D] [-f] [-m] [-N] [-R root] [-F [-n]] pool | id [newpool]
> 
> 
> Only the latter two offer -N.

Both forms that accept -N use it to import without mounting any filesystems.

> It might help if you showed your console session -- exact command, exact 
> output.

# zpool list backupA
cannot open 'backupA': no such pool
# zpool import -N backupA
# zpool list backupA
NAME      SIZE  ALLOC   FREE  EXPANDSZ   FRAG    CAP  DEDUP  HEALTH  ALTROOT
backupA   696G   189G   507G         -     1%    27%  1.00x  ONLINE  -
# zfs list backupA
NAME         USED  AVAIL  REFER  MOUNTPOINT
backupA      189G   486G    22K  /backup-ext/backupA
# zfs get canmount,mountpoint backupA
NAME        PROPERTY    VALUE                   SOURCE
backupA     canmount    on                      local
backupA     mountpoint  /backup-ext/backupA     local


It appears -N is ignored and the presence of canmount=on and mountpoint 
being set results in automatic mounting regardless of whether or not -N 
is given to the zpool import command.  The expected behaviour is that -N 
overrides canmount and mountpoint, leaving all filesystems in the pool 
unmounted.

Currently, I work around this by setting mountpoint=none at the root 
prior to exporting (all datasets inherit mountpoint). I would prefer to 
leave mountpoint set so that the automated task that uses the pools just 
has to import and export them without twiddling properties.