Not able to switch user postgres

hi i am not able to execute the command sudo su - postgrs

console hangs once i execute this command. my postgres server is not responding and i am not able to execute psql comand even. also i am not able to shutdown the server..


help me...

THis issue is resolved now actually issue was with system tuning.... my server had been eaten by zombie processes ...processor was almost killed by java processors i had to kill some process to pump life into the cpu.sorry for posting this issue here as it was related to system but as i was having problems with PostgreSQL so i thought that this was related to postgres