If for some reason you changed WAS Run As user and Run As group process execution and Deployment Manager is no longer starting up, change back both settings (user and group) in server.xml under this path: /usr_or_opt/IBM/WebSphere/App_Server/profiles/MyProfile/config/cells/MyCell/nodes/MyCellManager01/servers/dmgr
These notes are intended mainly for me but feel free to use them if you find them useful. I have many notes from way different topics, there is no specific one or correlation between them.