ReaR backup error: Mount command 'mount -v -t nfs -o rw,noatime ip::/sharepath /tmp/rear.xxx/outputfs' failed.

Issue

rear mkbackup failed with following mount error.

# rear -v mkbackup
Relax-and-Recover 2.4 / Git
Using log file: /var/log/rear/rear-vm76.log
ERROR: Mount command 'mount -v -t nfs -o rw,noatime 192.168.122.50::/public /tmp/rear.hfn8OnwCqGja2ap/outputfs' failed.
Aborting due to an error, check /var/log/rear/rear-vm76.log for details
Exiting rear mkbackup (PID 23681) and its descendant processes
Running exit tasks
You should also rm -Rf /tmp/rear.hfn8OnwCqGja2ap
Terminated