1. Stop the Deployment Manager...
   cd /opt/IBM/Portal/WebSphere/AppServer/profiles/Dmgr01/bin
   ./stopManager.sh -user wasadmin -password Wxxxxxxx

2. Start wsadmin.sh
   ./wsadmin.sh -conntype NONE -lang jython

   ...and run...

   AdminTask.renameCell('[-newCellName MBCellD -regenCerts false]')
   AdminConfig.save()
   exit

3. Edit DMGR_PROFILE/bin/setupCmdLine.sh and set WAS_CELL to new cell name

4. Start the Deployment Manager and check the SystemOut.log file for any errors.