I installed ubuntu 12.04 server on a Samsung net book "NP-N100S-E02 from a usb stick the first time I booted this netbook after purchased it, now I can't find usb boot options in the Bios setup. Always the boot devices priority has no more than the STA Toshiba harddisk. Somebody mentioned that Grub could put itself on the USB MBR, that's why maybe USB BOOT doesn't exist anymore. I'm asking if anybody confirm what I've been told or provide me with some advices on how to fix that, I'm really feeling lost
Technically grub can do that, but I find that rather unlikely. I suspect this is misconfigured BIOS.
Enable USB support in BIOS and twiddle with the boot order. Many BIOS also have a key to display a menu of available boot devices for you to select during boot.