Gfilui

I was following the (https://docs.mongodb.com/manual/tutorial/install-mongodb-on-ubuntu/) instructions to install MongoDB.

After completing till 4th step, i.e., after running the following command:-

sudo apt-get install -y mongodb-org

when I run mongo command to get the CLI, I am getting the following error:-

MongoDB shell version v3.6.4
connecting to: mongodb://127.0.0.1:27017
2018-04-20T12:02:10.947+0530 W NETWORK [thread1] Failed to connect to 127.0.0.1:27017, in(checking socket for error after poll), reason: Connection refused
2018-04-20T12:02:10.999+0530 E QUERY [thread1] Error: couldn't connect to server 127.0.0.1:27017, connection attempt failed :
connect@src/mongo/shell/mongo.js:251:13
@(connect):1:6
exception: connect failed

Also when I run sudo service mongod start, nothing happens. But when after that, I run sudo service mongod status, I get the following error:-

● mongod.service - High-performance, schema-free document-oriented database
 Loaded: loaded (/lib/systemd/system/mongod.service; disabled; vendor preset: 
 Active: failed (Result: exit-code) since Fri 2018-04-20 12:04:50 IST; 37s ago
 Docs: https://docs.mongodb.org/manual
 Process: 28034 ExecStart=/usr/bin/mongod --config /etc/mongod.conf (code=exite
 Main PID: 28034 (code=exited, status=217/USER)

Apr 20 12:04:50 Inspiron-N5010 systemd[1]: Started High-performance, schema-free
Apr 20 12:04:50 Inspiron-N5010 systemd[1]: mongod.service: Main process exited, 
Apr 20 12:04:50 Inspiron-N5010 systemd[1]: mongod.service: Unit entered failed s
Apr 20 12:04:50 Inspiron-N5010 systemd[1]: mongod.service: Failed with result 'e
lines 1-11/11 (END)

Can anyone help in resolving this issue?

It seems that the package is broken or package installation was interrupted.
Run:

sudo dpkg --configure -a

It will repair the package.

Also you first have to start the mongod server to use its cli.

So first run:

sudo service mongod start

and then run

mongo

This will open the mongodb cli.