For some reason Ubuntu server didn’t use all the available disk space while installing. Thankfully this is an easy fix.
sudo lvextend –resizefs -l +100%FREE ubuntu-vg/ubuntu-lv
If the Volume Group or LVM Volume is different, you will need to change the name in the above command. You can use the “sudo pvdisplay” and “sudo lvdisplay” to show you details about your volumes.