can you (theoretically) run only NFSv4 (without earlier versions)?

Robert P. J. Day rpjday at
Tue Dec 24 13:24:55 UTC 2013

Quoting Ed Greshko <Ed.Greshko at>:

> On 12/24/13 17:21, Tom H wrote:
>> On Tue, Dec 24, 2013 at 2:10 AM, Ed Greshko <Ed.Greshko at> wrote:
>>> After making the suggested changes.....
>>> [root at meimei ~]# mount -o ro,nfsvers=4 /mnt
>>> [root at meimei ~]# mount | grep mnt
>>> on /mnt type nfs4  
>>> (ro,relatime,vers=4.0,rsize=262144,wsize=262144,namlen=255,hard,proto=tcp,port=0,timeo=600,retrans=2,sec=sys,clientaddr=,local_lock=none,addr=
>>> [root at meimei ~]# umount /mnt
>>> [root at meimei ~]# mount -o ro,nfsvers=3 /mnt
>>> mount.nfs: requested NFS version or transport protocol is not supported
>> I tried disallowing v2 and v3 on Fedora 19 and failed.
>> "cat /proc/fs/nfsd/versions" shows that v2 and v3 are allowed by the
>> kernel and "mount -t -o nfsvers=3 ..." succeeds.
>> I ssh'd into a RHEL 6 box and an Ubuntu 14.04 VM where I know that v2
>> and v3 are disabled.
>> "cat /proc/fs/nfsd/versions" shows that v2 and v3 are disallowed and
>> "mount -t -o nfsvers=3 ..." fails.
>> I must've done something wrong on Fedora 19. I'll have to try again
>> later, but I can't see anything wrong in my setup offhand.
> On an F20 system where I'm doing the testing
> root at f20f ~]# cat /proc/fs/nfsd/versions
> -2 -3 +4 +4.1 -4.2
> Shows only 4 and 4.1 allowed.

   just to explain where this all came from, i was working off of what
i was seeing on a RHEL (actually CentOS) 6.5 system, where the config
file /etc/sysconfig/nfs had helpful comments which allowed me to
tweak that file thusly:

# Define which protocol versions mountd
# will advertise. The values are "no" or "yes"
# with yes being the default
... snip ...
# Optional arguments passed to rpc.nfsd. See rpc.nfsd(8)
# Turn off v2 and v3 protocol support

   if i make the above changes and restart NFS (on the RHEL system),
the *only* NFS-related entries i see in the output of "rpcinfo -p" are:

     100003    4   tcp   2049  nfs
     100003    4   udp   2049  nfs

and that's *it*, nothing more, which is what i expected.

   sadly, i don't have access to my fedora 20 box at the moment,
but all i was doing was trying to produce the same result --
only those two lines in the output of "rpcinfo -p". i can see
that the *effect* of the earlier suggestions is the same, in
that only NFSv4 is supported, but there is still that crud in
the output of "rpcinfo -p" that seems irrelevant.

   oh, and on the RHEL 6.5 system, the contents of the file
/proc/fs/nfsd/versions correctly contains:

-2 -3 +4 -4.1


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