“Operation not supported” error while accessing NFS mount

NOTE, it’s not permission error, that is another story!

This kind of issue could be all kind of reasons.

But, anyway, first of all, you should check the NFS version in your server and the client. Make sure you configure it based on the right version. Actually, the help info /etc/exports has this info, I quote

#
# Example for NFSv2 and NFSv3:
# /srv/homes       hostname1(rw,sync,no_subtree_check) hostname2(ro,sync,no_subtree_check)
#
# Example for NFSv4:
# /srv/nfs4        gss/krb5i(rw,sync,fsid=0,crossmnt,no_subtree_check)
# /srv/nfs4/homes  gss/krb5i(rw,sync,no_subtree_check)

So, make sure you use the correct config format in the /etc/exports.

In my case, both client and server use V4. At beginning, I used

/srv/homes       hostname1(rw,sync,no_subtree_check)

it didn’t work.

I changed it to

/srv/homes       hostname1(rw,sync,fsid=0,crossmnt,no_subtree_check,no_root_squash)

Now it works.

Do NOT forget to restart the NFS server after you make any change in /etc/exports.

Have a good day.