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To install/due-boot Linux on an EFI-capable computer with an pre-existing operating system, like Windows 8, the UEFI - Community Help Wiki at https://help.ubuntu.com/community/UEFI have covered it. Everything happens auto-magically. But I'd like to know what's going on under the hood. E.g.,

What should I do if I want to manually setup a second Linux system on this machine (on which both pre-existing Windows 8 and newly installed Linux are both booting fine)? The Grub2-efi should have already installed to the EFI boot partition. Do I still need to install it again? Or should I just add an Grub2 boot menu entry instead? Do I still need to install Grub2-efi to my second Linux system's partition? What are the minimum steps to manually setup Grub2-efi for booting this second Linux system on this machine?

UPDATE, further reading reveals that when using grub2-install to install grub2-efi, it will call efibootmgr to add an entry to EFI boot. My new new ASUS laptop EFI BIOS doesn't offer a BIOS menu to choose boot media. Each time I need to boot something different, I have to promote it up in BIOS, then save the BIOS, each time!. This would make it cumbersome for triple boot or multiple boot. Is there any easier solution?

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As a general rule, every Linux distribution will try to install its own boot loader (usually GRUB, but sometimes something else). Also as a general rule, every distribution tries to discover every available distribution, so when it installs its version of GRUB, that latest version will boot both its matched distribution and whatever had been installed before. Unfortunately, things don't always work out perfectly, so you may need to tweak the GRUB configuration manually, reconfigure the system so that another GRUB is the default boot loader, or use a boot manager other than GRUB as the default. In fact, there are so many possibilities that it's impossible to answer your question definitively. You can try it, hope for the best, and post here to to some other forum if you run into problems. You may also want to read up on EFI installations generally. There are three sites that I generally recommend for this:

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If your firmware's built-in boot manager is unsatisfactory, you may want to install another one.

Rod Smith also created rEFInd. It looks like a good choice to me. Once you've installed it it's supposed to scan for EFI-bootable OS's automatically. So you don't have to configure them all manually.

Also, you may want to think about how to re-install your boot manager in case it is lost. In a BIOS computer, the problem was that installing a new OS would overwrite the existing boot program. In EFI, the problem is that if you happen to reset the firmware settings (or, in some cases, upgrade the firmware), it will forget where the boot program is. Boot discs are Good To Have, especially linux live discs with working network drivers :).


An alternative possibility is the traditional (ab)use of the boot loader of one of your OS's, to provide a menu for all of the others. I.e. add custom entries into its GRUB menu, to chain-load the other loaders. I think it's relatively simple to add the entries, but it's extra complexity and potentially fragile. My Fedora laptop has never been able to boot Windows from GRUB for some reason, and I read other reports of the same. On Ubuntu I find it hard to even get into the GRUB menu (I think it's supposed to be hidden unless it detects another OS?).

I recommend avoiding the automatic os-prober from upstream GRUB, at least for booting multiple Linuxes. It requires that you notice kernel upgrades on the other installs, and run update-grub manually.

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