Is it possible to do an apt-get installation and continue it later?

Do apt-get install -d STUFF which will download everything to the cache but won't act on it.

Later when you have a better connection you can just drop the -d and apt will download the rest if needed and begin installing from the cache: /var/cache/apt/archives/

If you kill an apt-get while it's still in the stage of fetching packages then yes, it will resume fetching pretty much from where it left off - the archvies it has fetched so far will be kept in /var/cache/apt/archives.

This is the directory that gets cleaned up by apt-get clean, incidentally.

If you kill it after it's finished fetching and has started configuring/installing then you're in much deeper water and I wouldn't really want to try it ;)

Or, start the installation with GNU Screen. Just run screen by itself, and it will open a new window with a shell inside it. If you run commands here, then press Ctrl-d (^d), the window will "detach" from your current terminal, but it will stay running in the background: run screen -x to get back to it.

This also works for long-running command such as apt-get install [all of KDE]: just start the apt-get install command inside a screen window and press ^d. Then later, simply re-attach using screen -x and see if it's done.

Screen has much more options: ^a c will create new windows (use ^a 1 to go to the first one, ^a n to go to the one "to the right", etc). See http://www.gnu.org/software/screen/manual/ for the manual!

Edit: Of course, the computer running screen windows cannot be restarted, or the windows will be lost.