So this is what I had on the RHEL box: -
/etc/exports
/opt/IBM/WebSphere/AppServer*(rw,no_root_squash)
and this is I was seeing on the Mac: -
mount_nfs: can't mount /opt/IBM/WebSphere/AppServer from bpm855.uk.ibm.com onto /private/tmp/nfs: Operation not permitted
This post provided me with not ONE but TWO answers: -
which led me to Solution 1: -
sudo mount -t nfs -o resvport,rw bpm855.uk.ibm.com:/opt/IBM/WebSphere/AppServer /tmp/nfs/
and then Solution 2: -
/ettc/exports
/opt/IBM/WebSphere/AppServer *(rw,no_root_squash,insecure)
sudo mount -t nfs bpm855.uk.ibm.com:/opt/IBM/WebSphere/AppServer /tmp/nfs/
which is nice.