I installed sarge through netinstall and downloaded ~500MB after that (X, kde, gnome and stuff). I'd like to be able to save these packages and update only the necessary, the next time I need to do this. And that'd be soon as I have ordered a new hdd.
I went to /var/cache/apt/archives, but found only 92MB, and no X, kde or something (just xfce4 which I installed, and other minor things...). Did sarge delete those? Where can I find them? Is there any way to prevent me from downloading 500MB again?

Thanks!

The /var/cache/apt/archive directory is meant to be temporary storage. apt-get and other package installers have a command called "clean" which deletes the contents of this directory to save space. If the packages have disappeared from this directory you probably are not getting them back.

I am not sure why you want to keep the files around unless you are installing multiple systems. For a single system you typically do not need the .deb files once they have been installed; to upgrade packages you have to download the entire upgraded package again.

If you are installing Debian on multiple machines then there are some tools that can cache your .deb files more permanently. The most useful one I have found is "apt-proxy", which transparently creates a partial mirror in some directory you create. Unfortunately apt-proxy is in a state of transition now, and if you want it you should visit http://apt-proxy.sourceforge.net to get a copy. (You want version 1; version 2 is very buggy.)

The apt-proxy page has a list of alternative tools as well. The only other one I have used is "apt-move", which is a package that does exist in the official Debian archives. Making mirrors with this package requires more manual intervention, however.

You could always try partimage, which is like Norton Ghost and make an image of your hdd. Just tried it myself for the first time, and isnt too painfull at all. At least that way you dont have to go through the whole install again and the whole setting it up how you like it.

Thanks guys. I know partimage. I made a successfull backup of my home dir, but the root fs didn't boot ok. The famous 99 99 99... error. I didn't bother to fix it, just installed from scratch.
Another way would be to build a local repository, which is more adequate here, as I have a tiny server with spare disk space.
Apt-proxy sounds cool, though. I'll take a look.