I had to use the recovery mode, since I've removed unintendly the KDE desktop. What was a bad surprise, that although I had all the packages in /var/cache/apt/archives , I could not reinstall them with aptitude. It wanted to download them, but since I didn't have established connection, the download failed. i don't understand why did I have failure, when I have all the required packages in cache? Is it possible to change it?