while trying this mongo command in ubuntu I am getting this error.
ritzysystem@ritzysystem-Satellite-L55-A:~$ mongo
MongoDB shell version: 2.6.1
I faced the same problem, so please check is there mongodb folder, firstly try to remove that folder
rm -rf /var/lib/mongodb/*
Now try to start mongo and if same problem then its mongodb lock file which prevent to start mongo, so please delete the mongo lock file
rm /var/lib/mongodb/mongod.lock
For forcefully rm -rf /var/lib/mongodb/mongod.lock
service mongodb restart if already in sudo mode
otherwise you need to use like sudo service mongod start
or you can start the server using fork method
mongod --fork --config /etc/mongod.conf
and for watching the same is it forked please check using the below command
ps aux | grep mongo