[mythtv-users] [OT] Problem getting recordings working with NFS

[Mike Perkins]

On 17/10/13 13:58, Stephen P. Villano wrote:
>
> On 10/17/13 8:46 AM, Dan Wilga wrote:
>> On 10/16/13 11:33 PM, Phill Edwards wrote:
>>> I am no expert at all with NFS, but I just checked my working
>>>
>>>      /etc/exports, and the thing that I can see that is different is the
>>>      fsid values.  Your first (root) entry should be fsid=0, and all the
>>>      others should be different integer values.  The fsid identifies the
>>>      filesystem and has to be different for each entry.  I just have mine
>>>      as 0, 1, and 2.
>>>
>>> Thanks so much, you hit the nail right on the head! The problem was
>>> indeed because I had duplicate fsid values. Are you sure you're not
>>> an expert :)
>>>
>> I've been using NFS for many years, and have never seen a need for the
>> fsid parameter. IMHO, it's probably best to just leave it out and let
>> NFS derive a number by itself. It will use either the UUID or the
>> device number. It's only in the rare case where a particular device
>> has neither of these that you need to add this parameter.
>>
> To tell the truth, my other NFS points don't use fsid, only the one on
> the large fakeraid. Can't recall *why* I ended up resorting to fsid,
> might have been that the device number wasn't usable by nfsd to derive
> its own number though.
> An example of my other exports file entries is below:
> /var/lib/mythtv/recordings
> 192.168.0.0/24(ro,async,no_root_squash,no_subtree_check)
> I toyed with the notion of setting it rw, but as I don't write to those
> directories from remote systems, I didn't bother.
> If I need to manually write to those directories, I'll do it via my ssh
> session.
>
It is to do with the version of NFS that your system is using. NFSv3 is the 
'traditional' method that works the way everyone is used to and does not use the 
fsid parameter.

NFSv4 is the newer version and is designed to get round some of the problems in 
previous versions. This imposes a 'tree' structure on your exports and the 
'root' of the tree requires an fsid=0 parameter to identify it. Other exports 
are always below this; to coerce the tree structure from exported directories 
often requires strange options to reposition directories under the NFS 'root'.

The defaults have changed recently - for my case, Debian, at least - and my 
systems now default to assuming NFSv4. This can be overridden to give NFSv3 but 
requires adding obscure parameters to odd, poorly-documented daemons. I haven't 
found an easy way to ensure NFSv3 on all my systems yet :(

I'm no expert in NFS but I've managed for fourteen years or so without trouble 
until recently. Why they had to spring this change on everyone without much 
explanation I don't know.

-- 

Mike Perkins