I have a Samsung ATIV Book 8 with Windows 8.1 and Ubuntu 13.10 on the internal 1T drive. Recently I acquired a 250G external USB hard drive. I booted the Samsung from the same USB thumb drive that I had used to install Ubuntu 13.10 on the internal drive but chose to install Ubuntu 13.10 on the entire external USB 250G hard drive, but, and this is important, I set the device for the bootloader as /dev/sda5 which is the boot partition on the INTERNAL drive for the original Ubuntu.
Now - with the external USB drive connected, I hit F10 and boot from the Linux boot loader which brings up the Grub2 menu and I can choose either of the two Ubuntus (the internal or the external) and boot and all is well.
If I disconnect the external USB drive and hit F10 on boot up and select the Linux boot loader, I do NOT get the grub2 menu, and can not choose to boot from the internal Ubuntu. I get an error and it drops immediately into grub in a terminal.
So, the problem is, IF I do not have the external drive connected, I can NOT get to the grub2 menu and therefore can not boot to the INTERNAL Ubuntu.
Any advice would be greately appreciated.
Update 12/3/2013 --- Well, I have not solved it yet, and I do not understand it yet but I have found a work-around. If I boot the Samsung without the external drive connected, I get dropped into the grub CLI. I can then issue the following commands and it will boot Ubuntu from the internal drive.
grub> linux (hd0,5)/boot/vmlinuz-3.11.0-14-generic root=/dev/sda5
grub> initrd (hd0,5)/boot/initrd.img-3.11.0-14-generic
I am just posting this in case it may somehow help someone else. I am sure when I have time to read more about groub2 (which is great) I will understand it and fix it correctly.
Thanks for reading