Thank you Xylos for your reply.
I think I might have cloned the wrong partition.
Here is the snapshot when I run the commands as instructed by you
# partition table of /dev/sda
/dev/sda1 : start= 63, size=390636477, Id= 7, bootable
/dev/sda2 : start=390637566, size=234504194, Id= 5
/dev/sda3 : start= 0, size= 0, Id= 0
/dev/sda4 : start= 0, size= 0, Id= 0
/dev/sda5 : start=619139072, size= 6002688, Id=82
/dev/sda6 : start=390637568, size= 97654784, Id=83
# partition table of /dev/sdb
/dev/sdb1 : start= 63, size=1953520002, Id= 7
/dev/sdb2 : start= 0, size= 0, Id= 0
/dev/sdb3 : start= 0, size= 0, Id= 0
/dev/sdb4 : start= 0, size= 0, Id= 0
What happens is I have two operating systems (Windows XP and Ubuntu) installed on this machine. And what I'd like to clone only is the Ubuntu OS partition.
I am just having a guess here - could it be /dev/sda1 for the ubuntu OS
The external HD (1TB) or sdb1 should be much bigger to accommodate the clone.