It was fine 2 days ago, Now mongod does not work. Even echo ps -A | grep mongo printed nothing, yet it warns about error: \"Only one usage of each sock
mongod
echo ps -A | grep mongo
try to start mongo on a different port: http://docs.mongodb.org/manual/reference/mongod/#cmdoption-mongod--port
to be sure what port you can use, execute the command Sriukanth Venugopalan mentioned, it will list the current ports being used.
Regards, Moacy