[OpenIndiana-discuss] nfs mounting and cascading dataset access?

[Doug Hughes]

On 2/27/2012 11:32 AM, James Carlson wrote:
> Scott LeFevre wrote:
>> I have a pools setup named tank1 with multiple datasets/filesystems
>> defined.  At the top, I have tank1/media followed by tank1/media/Video
>> and tank1/media/Music.  I've setup tank1/media as a nfs share
>> (e.g. /export/media) and can mount it from other systems.  When I try to
>> access media/Video from the nfs client, it shows an empty directory.
>> (From the oi 151a2 host, everything shows up locally.)   I can mount
>> tank1/media/Video directly from the nfs client and everything shows up
>> as it should.
>>
>> Is there a way to make this work where I expose just tank1/media as an
>> nfs export and can access the underlying datasets/filesystems (e.g.
>> Video and Music)?
> This isn't really a special issue with ZFS.
>
> NFS has always done exports by file system.  If you have /foo and
> /foo/bar, and /foo/bar is a mount point for some other file system, then
> exporting /foo does not give clients access to the contents of /foo/bar,
> because there's no way to cross the file system boundary.  Instead,
> clients looking at /foo/bar will see there whatever is actually in the
> /foo file system -- probably just an underlying empty directory used as
> the mount point.
>
> What you can do is set "sharenfs=on" (or some list of NFS options
> instead of just "on") using the zfs command on tank/media, and all of
> the filesystems under that point will inherit this setting.  That means
> that clients will see separate NFS exports for each of the underlying
> datasets -- one for Video and one for Music in this case.
>
> Automount, of course, is your friend.  ;-}
>
You can do this (hierarchical implicit shared subfs) with NFSv4, but not 
with NFSv3. There's a lot more setup for V4 though and it would likely 
not be as robust.