Lately I updated our lab's server to Ubuntu 16.04 LTS. I did a clean installation but the system won't boot up. It stuck with a blank ubuntu wallpaper screen and nothing showed up. Looking at the system logs it shows an error saying things like
Kernel Panic xxx
After digging a bit, it's because of UNETBOOTIN. I am using a Mac to burn the Ubunto ISO to the system and it seems UNETBOOTIN has some issues to initialize some parameters. Later I switched to a Windows machine and used "Linux Live USB creator" to re-create a bootable USB flash drive. And this time it works perfectly.