How to move Ubuntu installation from one hdd to another?

Clonezilla may be useful for cloning your hard disk, even for those situations on which you need to do it with different size disks as mentioned here: http://www.tuxradar.com/content/how-clone-hard-drives-clonezilla

Moving to a bigger disk

It's easy to ensure that a clone of a SCSI disk is restored to a SCSI disk, but you'll have a tough time finding an exact replica size-wise. The good news is you don't have to restore a disk on another disk of the same size. The even better news is that you can in fact restore the image to a much larger disk.

When restoring a disk, Clonezilla enables you to resize the filesystem and create partitions on the new disk proportionally. But even if you are moving to a bigger disk, you might prefer to keep the partitions as they are. In that case you can ask Clonezilla to create the partition table as its listed in the image.

There is documentation about moving to a larger disk as mentioned here but I am not sure that you can do it the opposite (cloning to a smaller disk).

However, it's worth to try. Clonezilla offers several Live CD's and bootable USB images and there is also documented that you can resize the free space on the disk after the copy, in which case the suggestion by @maniat1k to use gparted is also a good idea.

If you use clonezilla, I would appreciate if you drop comments with your experiences over here in order to have well documented how does this work for future reference.

Thank you a lot and Good luck!

1. Time consuming and perfect copy, with the bits in the same order on the disk is made with the unix command dd. Boot off your CD and open Disk Utility (palimpsest). Identify the device IDs of the two hard drives, for instance /dev/sda (the old hard drive) and /dev/sdb (the new one). Next, copy directly with the command dd if=/dev/sda of=/dev/sdb in this case. That step will take days even if the disk is not full. Lastly, open up Disk Utility (palimpsest) again and expand the partition to cover the whole 300GB drive and update grub.
2. Another way would be to do a complete install on the other drive and then copy over your home folder.
3. Also, you could simply take a directory and move its contents to the other drive and place a symbolic link from one drive to the other to save space - I do this for my ~/.wine folder on my Ubuntu-running desktop.

Just putting in the new drive and copying over all the files by themselves will not work because the disk will not be listed in GRUB and the partition is not set as bootable.