I have a 1TB disk, /dev/sda. I installed Ubuntu using default options and it took up the whole disk.
I would like to install Ubuntu in a 200GB partition and leave the rest for data so that I can refresh my Ubuntu as and when I like it without destroying my data.
I see that under Installation Type
there is Something else
where I can specify the partition size. However, when I tried it it keeps saying something like no file system at /. How do I use this option to install Ubuntu on 200GB, assuming that this is a fresh disk and nothing currently on it need to be preserved?