I cloned my linux system disk with clonzilla. Ifs very straight ward, the video below shows you how I did it. Better than my other video as I recorded it into a HDMI capture card, gets around the dodgy camera angle of last time.
I needed more space in my home server so got another two 6TB drives, and I decided to also replace the system disk as it is pretty old. I cloned the existing drive using Clonzilla and then expanded the partitions to fill the available space. Check out the video for the full details.