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Bib-lost
Asked: 2017-08-19 08:09:37 +0800 CST

Dual-boot without bootmanager, i.e. to have a default boot OS

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I'd like to make my (Windows 10) desktop computer into a dual-boot system Windows-Ubuntu. However, since Windows 10 will be the most used operating system by far, I wonder if it's possible to do this in such a way that the computer always automatically boots into Windows, preferably without showing any bootmanager and without a significant decrease in speed compared to the current single-boot situation. Ubuntu would then have to be accessed by a one-time-boot menu, triggered by pressing a button during startup (probably F12 on my system).

Is this possible at all and how should I go about this?

dual-boot

1 Answers

  1. Best Answer

    Broadly speaking, there are two ways to do this:

    • Configure Windows first in the EFI boot manager -- After installing Ubuntu, type sudo efibootmgr. This will show you a list of boot programs, which should include both ubuntu and Windows boot manager. Each of those will have an associated number (Boot####). There will also be a BootOrder line that shows the order in which boot entries are tried. Chances are Ubuntu will be first in the boot order and Windows will be second. You can reverse that order by using the -o option to efibootmgr. For instance, suppose Ubuntu is Boot0008, Windows is Boot0003, there are a couple more entries, and the current boot order is 0008,0003,0006,0005. In this case, you might type sudo efibootmgr -o 0003,0008,0006,0005 to reverse the Windows and Ubuntu boot orders. You can do the same thing in a GUI way in Windows by using the third-party EasyUEFI tool. When you're done, Windows will boot by default; and to boot Ubuntu, you'll need to hold whatever key your computer uses to enter its built-in boot manager, which will enable you to select the ubuntu entry.
    • Configure Windows first in GRUB (or another user-installed boot manager) -- Instead of relying on the EFI boot manager, you can leave GRUB as the first boot entry and configure it to boot Windows by default. You can also adjust the timeout and configure GRUB to not display its menu unless you hold (IIRC) the Shift key. Such changes are normally made via an assortment of GRUB configuration files and then running sudo update-grub; however, the GRUB Customizer utility helps you to do this in a GUI way. (I'm not much of a GRUB person so I don't know a lot about GRUB Customizer and can't help beyond a pointer to the PPA.) You can do similar things with my own rEFInd or other boot managers, but details differ, and these would require installing extra software, so you're probably best off reconfiguring GRUB for your needs, unless you find that you can't do quite what you want.

    Note that what was a boot medium selector in BIOS-based computers has been expanded into a boot manager in most EFI-based computers. Under EFI, there should be options to boot particular OSes (or their boot loaders, to be more precise), not just disks. If you don't see such options after installing an OS, then chances are you firmware is defective, or at least very poorly designed. In this case, you may have no choice but to rely on GRUB or some other boot manager to do what you want.

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