See installed packages

On old.server.com make list of installed packages.

dpkg --get-selections >> /tmp/installed_pkg.lst

Install a new Ubuntu with same packages

If you want a new server to have the same packages as the 'old.server.com

scp heth@old.server.com:/tmp/installed_pkg.lst /tmp
dpkg --get-selections < /tmp/installed_pkg.lst
apt-get install dselect
dselect

In the dselect menu select menu item 3 - Install