Install package

sudo dpkg -i DEB_PACKAGE

See details on http://askubuntu.com/questions/40779/how-do-i-install-a-deb-file-via-the-command-line

List installed packages

dpkg --get-selections | grep postgres
dpkg -l

See details on http://askubuntu.com/questions/17823/how-to-list-all-installed-packages