Hi there @adminClam,

As this is a major version upgrade, I would strongly recommend 3 things:

• Make sure to take a snapshot of your server before running the command, that way in case anything goes wrong you would still be able to revert to a working instance

• Make sure to schedule some downtime period and do it when you do not usually expect as much traffic

• Go through this step by step tutorial on how to do the upgrade:

https://www.digitalocean.com/community/tutorials/how-to-upgrade-to-ubuntu-16-04-lts

Hope that this helps.
Regards,
Bobby