I upgraded from Ubuntu 11.10 to 12.04 using bootable USB. After upgrade, all non-default packages from 11.10 are gone. For ex, I did not have Chromium, Eclipse etc. Although, I could see these in the History in the "Ubuntu Software Center". Is there any way I can retrieve all these packages (even reverting back to 11.10 is also fine with me)? What could be a possible reason for this (We plan to upgrade a few more machines)? During the upgrade process, I had unchecked the box which asked permission to look online for upgrade/packages. Co