I have an Ubuntu Server VM running on TrueNAS.
Well, I started out with a 10GB disk but upon installing python packages and whatnot was quickly running low...
Naturally, I tried to find how to increase the space within the TrueNAS GUI until I saw I could increase the Zvol size from Storage>Pools>MyPool>MyUbuntuDisk and then Edit Zvol.
BUT that didn't take effect within the VM. So I ran lsblk and df -h only to see the new disk size didn't take effect.
I found a blog post (below) but it didn't work until I figured out how to resize the disk within Ubuntu.
I was out of space so I couldn't install Gparted (and maybe also an xserver?)
So I added an Ubuntu Desktop .iso as a CD...
then followed the instructions on the blog! Yay!
under the hood it looks like gparted runs lvm pvresize -v '/dev/sda3'