Hey there, I've set up a new instance (Amazon AWS EC2) to install nodeBB. I've been following the instructions here:
https://docs.nodebb.org/en/latest/installing/os/ubuntu.html

and up until the point where it says:

$ mongo -u your_username -p your_password --authenticationDatabase=admin

it seemed to work fine (for a change, in my case). I've tried the username for mongoDB as well nodeBB defined just a few steps earlier with the same results.
Here is what I get in return:

MongoDB shell version: 3.2.12
connecting to: test
2017-02-12T19:16:21.567+0000 W NETWORK [thread1] Failed to connect to 127.0.0.1:27017, in(checking socket for error after poll), reason: errno:111 Connection refused
2017-02-12T19:16:21.567+0000 E QUERY [thread1] Error: couldn't connect to server 127.0.0.1:27017, connection attempt failed :
connect@src/mongo/shell/mongo.js:229:14
@(connect):1:6
exception: connect failed
ubuntu@ip-172-31-30-62:~$ D

Mind, this was a 'clean' install. Should I have configured something else before proceeding?
Hints to some guides or concrete how-tos are so very welcome, I'm on it - and similar trys - for several days now. Please help.