Copying Ubuntu from a 20 Gig Hard drive to a 100 Gig Hard Drive?

[Alfred]

Hi: 
Copying Ubuntu from a 20 Gig Hard drive to a 100 Gig Hard Drive?

Is this simple or difficult to do?

I'm running out of space, on my 20 Gig Hard drive, but have about 100
Gigs left on another drive. Can I copy the whole root partition .eg the
whole operating system, with all the directories to a bigger hard drive,
with a few commands in terminal mode, or can it even be done, in Gnome?

Alfred!