In my case, I had a template VM in ESXi that I deployed and needed to add tons of disk space to – up to 9TB.
First, I’d suggest using cfdisk instead of fdisk – it’s got a pseudo-UI so you can see it (for those of us who don’t have as robust of a mental abstraction of command line output).
When I tried to write the changes to disk I got a message that since the disk was MBR the max size the volume could be was 2TB. Ummm….. now what?
Well, convert it to GPT of course! This can be a dangerous effort, or so it seams, but since this was a brand new machine deployed from a template, I had nothing to lose. Here’s a step-by-step that worked: https://johnlewis.ie/converting-to-gpt-in-ubuntu/
I did this a little over a week ago, but it actually worked the first time. Just make sure you get your “sda2” and “sda3” – or whatever they actually are for you – correct.