===== Πηγές =====
  * Εντολές διαχείρισης πακέτων : http://osdir.com/ml/ubuntu.doc/2005-05/msg00085.html
  * Become an apt guru : http://maketecheasier.com/become-an-apt-guru/2009/02/24
  * pre-removal script returned error : http://ubuntuforums.org/archive/index.php/t-444492.html
  * backports : http://www.backports.org/dokuwiki/doku.php?id=instructions