I have recently installed Ubuntu 9.04 on my USB key by means of the Ubuntu Startup Disk Creator with determination enabled as well as have been gladly running Ubuntu from it for awhile.

But, now 9.10 have arrived plus I would like to upgrade. If I upgrade from the key, then do all the upgraded packages take up space on the casper-rw part of the disk?

If so, how do I restore the set up produced by the 9.04 version to the one formed by the 9.10 version without overwriting my changes in casper-rw? Should we have a tool for this process?