Re: Buyer Beware: A Major Change in NFS (in Rawhide) is about to happen

[Steve Dickson <SteveD redhat com>]

On 10/26/2009 12:06 PM, Frank Ch. Eigler wrote:
> Steve Dickson <SteveD redhat com> writes:
> 
>> [With the next nfs-utils rawhide build, I will be flipping the ]
>> [switch that will cause all NFS client mounts to try NFS v4 first ]
>> [...]
> 
> Is this really "first" or rather "only"?  Was there a conclusion about
> whether the nfs client code would be changed to fall back from v4 to
> v3 automatically?
It meant "first"... If the server does not support V4, the mount will
automatically roll back to v3/tcp,v3/udp,v2/tcp,v2/udp... 

The problem comes in when the server does support v4 but the exports are 
not configured correctly (like pre F-12 Linux servers). In that case the 
mount will fail with ENOENT which will look like:

mount.nfs: mounting laptop:/home failed, reason given by server:
  No such file or directory

The there are a couple fixes to this problem:
   1) Upgrade to an F-12 server
On a pre F-12 Server:
   2) Added the '/ *(ro,fsid=0)' entry to the /etc/exportsfile and 
      reset the exports with 'exportfs -arv' (see exports(5) for details).
   3) Set the 'RPCNFSDARGS="-N 4"' shell variable in the /etc/sysconfig/nfs
      file and restart the server via 'service nfs restart'
On a Rawhide Client:
   4) Set the Defaultvers=3 in the /etc/nfsmount.conf file
   5) Explicitly set the version (meaning don't do any server negotiation)
      by either using the '-o v4' mount option on the command line or 
      set  Nfsvers=3 in the /etc/nfsmount.conf file.

The first fixes two are preferred...

steved.