MongoDB --- Failed global initialization: Failed to open "/var/log/mongodb/mongod-config.log"
So, I have figured out my own question.

Firstly, the issue was that since I was using a different port 27019 for the config servers, I needed to open that port from the firewall.

Second, I changed the dbPath in my config file from /var/lib/mongodb to /data/db since that is the default path for mongodb to store data. 

Make sure to run sudo service mongod restart after.

With that done, I was able to start mongod with my specific config file:

sudo mongod --config &lt;path-to-config-file&gt;


The key is to include sudo for me. That solved the issue of:

F CONTROL  [main] Failed global initialization: FileNotOpen: Failed to open 
"/var/log/mongodb/mongod-config.log"


After running the command, I see that mongod has started on my virtual machine (vm) and now I am able to connect to the mongo shell of said vm from another machine with:

mongo &lt;ip_address_of_said_vm&gt;:27019