OpenBSD – Image on a new, bigger disk – how to use the extra space

Instead of creating new partitions, look at resizing your existing partitions. For this, I use GParted.

http://gparted.sourceforge.net/

Specifically, I use the GParted Live CD which you can just boot into from CDROM.

http://gparted.sourceforge.net/livecd.php

With it, you can resize your partitions and most file systems (excepting some LVM and/or MD sets.)

Once done, you can reboot back to your hard disk and you're good to go.

I've used this both in physical and virtual environments. In a VM environment, it's great for keeping around small template VM's that can be "sized-up" for larger applications.

I managed to solve this rather simply. I installed parted and when I ran that it informed me that the partition table didn't cover the full disk (duh), so it asked me Fix/Cancel to which I responded with Fix. Apparently, that did the trick as I was able to modify the partition to the full size using sudo fdisk /dev/vda, but afterwards I did need to run sudo resize2fs /dev/vda3 to have the changes applied.