Fixed error "reason: error:111 Connection refused OR exception: connect failed" issue during mongoDB restart service in ubuntu 16.04

I got the problem like below during start the Mongo DB service after it's installation.

Problem:

root@root: mongo
MongoDB shell version: 2.6.12
connecting to: test
2016-08-26T11:32:14.847+0530 warning: Failed to connect to 127.0.0.1:27017, reason: errno:111 Connection refused
2016-08-26T11:32:14.849+0530 Error: couldn't connect to server 127.0.0.1:27017 (127.0.0.1), connection attempt failed at src/mongo/shell/mongo.js:146
exception: connect failed

Solution: Run below commands to fix

sudo rm /var/lib/mongodb/mongod.lock

then

sudo service mongod restart

Output:

root@root:~$ mongo
MongoDB shell version: 2.6.12
connecting to: test
Server has startup warnings: 
2016-08-26T11:39:54.807+0530 [initandlisten] 
2016-08-26T11:39:54.807+0530 [initandlisten] ** NOTE: This is a 32 bit MongoDB binary.
2016-08-26T11:39:54.807+0530 [initandlisten] **       32 bit builds are limited to less than 2GB of data (or less with --journal).
2016-08-26T11:39:54.807+0530 [initandlisten] **       Note that journaling defaults to off for 32 bit and is currently off.
2016-08-26T11:39:54.807+0530 [initandlisten] **       See http://dochub.mongodb.org/core/32bit
2016-08-26T11:39:54.807+0530 [initandlisten]
>