Netgear Readynas Duo, NFS and Debian Sid: mount.nfs: Operation not permitted

Today I spend some time to mount one folder on Readynas Duo with NFS. All goes right from server (Debian Lenny) but i can’t mount NFS partitions from my pc (Debian Sid).

Error was “mount.nfs: Operation not permitted “.

Ok, I check my mount options

#cat /etc/fstab <ipaddress>:/c/folder  /mnt/folder nfs rw,user,noauto 0       0

Fstab is ok but problem persists.

Request mount to be verbose (from my pc – debian sid)

<myhost>:/home/giulio# mount -v /mnt/folder
mount.nfs: timeout set for Sun Jan 17 13:34:47 2010
mount.nfs: trying text-based options 'addr=<readynas-ip-address>,vers=4,clientaddr=<my-pc-address>'
mount.nfs: mount(2): Operation not permitted
mount.nfs: Operation not permitted

Request mount to be verbose (from my server – debian lenny)

mount.nfs: trying <readynas-ip-address> prog 100003 vers 3 prot TCP port 2049
mount.nfs: trying <readynas-ip-address> prog 100005 vers 3 prot UDP port 3078
<readynas-ip-address>:/c/folder on /mnt/folder type nfs (rw,noexec,nosuid,nodev,noauto,user)

Wow, ok, there is a difference.

My pc try to mount nfs with version 4, my server doesn’t use v4,  but it uses v3!

What is strange?
I’ve read a lot of tutorial/faq but my problem remains. So I read man pages but this is what I find, for example in man mount.nfs…

mount.nfs is meant to be used by the mount(8) command for mounting NFS shares. This subcommand, however, can also be used as a standalone command
with limited functionality.

mount.nfs4 is used for mounting NFSv4 file system, while mount.nfs is used to mount NFS file systems versions 3 or 2.  remotetarget is  a  server
share usually in the form of servername:/path/to/share.  dir is the directory on which the file system is to be mounted.

It seems to be false. On my pc I use mount.nfs and always mount tries with nfs4.

Ok, let’s go to solution..

You can force the NFS version to use with nfsvers=3.

So I change my /etc/fstab like this:

<readynas-ip-address>:/c/folder /mnt/folder nfs rw,user,noauto,nfsvers=3  0       0

Now mount uses the right version and all goes well.

Bye!