MongoDB is not starting. I have installed mongo and mongo was running but after reboot it is not running.
ERROR: Cannot write pid file to /var/run/mon
The MongoDB packages contain a "bug" which prevents them from starting properly on the newer RedHat based systems. Please see SERVER-14679 for details.
As a workaround until 2.6.5 is released, please edit the init script according to https://github.com/mongodb/mongo/commit/50ca596ace0b1390482408f1b19ffb1f9170cab6