I ran into ugly problems with ubuntu lack of updated repos for mongodb. It seemed it was working but when i start running the console for mongo /usr/bin/mongo and not just mongod then errors started appearing. So I did a bit of research and find a way to install the latest mongo as of this blog post. After that i had to run:

In one shell:

~ mongod

In another shell:

~ mongo
// and configure the authentication

The authentication commands are located here.

The most problematic point was because I had a process `mongo` running on the background and had to kill it with su:

~ ps -ef | grep mongo
~ sudo killall mongo -s 9

Now everything is:

~ mongod --version
db version v2.0.4, pdfile version 4.5
Thu Apr  5 17:37:11 git version: sha1
~ mongo --version
MongoDB shell version: 2.0.4

I am so excited about working the right way with mongodb!