misc/161496: Please document that sysctl vfs.usermount must be 1 for zfs-allow'ed user mount delegation to be allowed

[Karl Lehenbauer]

>Number:         161496
>Category:       misc
>Synopsis:       Please document that sysctl vfs.usermount must be 1 for zfs-allow'ed user mount delegation to be allowed
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          doc-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Oct 11 16:50:07 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator:     Karl Lehenbauer
>Release:        8.2-STABLE
>Organization:
FlightAware LLC
>Environment:
>Description:
Please add a note to the zfs manpage that even if zfs allow is used to allow a user to mount their own zfs filesystems, that FreeBSD will not allow it unless the sysctl vfs.usermount is set to 1.

The error message zfs returns...

cannot mount 'tank/backup/oscar/pgsql': Insufficient privileges

..provides no hint of what's wrong, either.
>How-To-Repeat:

>Fix:
Update the zfs manpage.  Thanks!

>Release-Note:
>Audit-Trail:
>Unformatted: