To begin, you don't have a BIOS; you have an EFI (a UEFI, really; UEFI is EFI version 2.x). EFIs boot in a very different way from BIOSes. Unfortunately, many people, and even manufacturers, apply the term "BIOS" to their EFIs. This leads to confusion because people try to apply BIOS concepts to their EFIs, and this often leads to mistakes. That may not be the cause of your problems, but it might be playing a minor factor. I recommend you read a couple of pages on EFI-mode Linux installations before you do anything else:
The old BIOS boot-order options are more sophisticated under EFI, because under EFI, you boot from a file, so you can have multiple boot options on a single hard disk. These are typically named, not just identified by a disk; but in the case of removable disks, the entries are likely to be identified by the disk's manufacturer and/or model. Furthermore, most EFIs support both native EFI-mode boots and boots of BIOS-mode boot loaders via a component known as the Compatibility Support Module (CSM; aka "legacy mode" booting). Thus, setting your external medium to boot first is somewhat ambiguous; it might be trying to boot in BIOS mode or in EFI mode. Many EFIs are flaky even there, and may not do what you expect. They might forget to boot from the external medium first if you unplug that boot medium, for instance.
Instead, I recommend you learn to use the computer's built-in boot manager. This may require disabling the firmware's "fast startup" features. You can usually get to the boot manager by hitting a function key (usually a high-numbered one), Esc, or Enter; but details vary from one computer to another, so you may need to consult the computer's manual to learn how to get to this menu. Once you've found it, you should be able to launch the installer by selecting its option on the menu -- but if two such options appear, select the one that includes the string "UEFI." The one that does not include that string likely boots in BIOS/CSM/legacy mode, which you do NOT want to do on your computer!
If you can only launch the boot medium in BIOS mode, it's probably missing an EFI-mode boot loader. This can happen because some programs used to create boot media omit the EFI-mode boot loader. Thus, you may need to try another tool, like Linux's dd
command or Rufus.
The symptoms you describe (getting a grub>
prompt if you try to boot with the external disk disconnected) are caused by the weird way Ubuntu configures GRUB, in conjunction with your external-disk installation. In particular, the main GRUB binary resides on the EFI System Partition (ESP), which in your case is on the internal disk; but this program relies on configuration files in the /boot/grub
directory, which in your case is on the external disk. When GRUB can't read its configuration file, it presents a grub>
prompt; and exiting from GRUB will then launch whatever's next in the EFI's boot order. This boot-time quirk will go away when you install Ubuntu to your internal disk; but if you wanted to keep Ubuntu on the external disk, you could work around the problem in various ways, such as by moving Ubuntu's /boot
directory to a small dedicated /boot
partition on the internal disk or by switching to another boot program that doesn't split its configuration file off in the way GRUB does.
If you continue to struggle, you might consider installing my rEFInd boot manager. As I've noted, some EFIs have flaky built-in boot managers, and rEFInd is likely to do a better job, with the caveat that you may need to hit the Esc key once the rEFInd menu appears to get it to scan your external media. rEFInd will also not be affected by the GRUB multi-disk configuration file issue, so it would be a way around that problem, if you decide to keep Ubuntu on the external disk.
sudo parted -l
If it says DOS or msdos then you have the 4 primary partition limit and need one extended to allow many logical partitions. askubuntu.com/questions/149821/… IF gpt then you are installed in UEFI mode and gpt limit is 128 partitions which even can be changed to more.unetbootin
to extract the content of the iso fileubuntu-16.10-desktop-amd64.iso
to a usb in order to boot it and install Ubuntu... I've set the booting order from the BIOS to boot first from usb drive. What happens is that a grub terminal appears as usual where normally I hit exit and the installed win 10 os loads as regular... when the external drive where I've installed ubuntu is connected to the laptop this screen doesn't show up but a dual but choice screen appears which after the countdown it boot ubuntu.