Henry W. Peters posted on Sat, 21 Sep 2013 13:38:58 -0400 as excerpted: > One other thing I have been meditating upon, is that I have a UEFI > bios... (Windows 8), I did install an MBR on the external disk, with > grub on it... & when I boot, in legacy mode, from it... grub works... so > thinking I might be able to update grub, after the Gentoo install, & > (hopefully) use grub to load the Gentoo system... Grub would not install > in the UEFI, & the directions to boot from it, with Linux, are a bit > complex for me at this stage... (will try to work that out too, > eventually).
You don't mention what version of grub you're talking about. I haven't used grub's UEFI modes personally (see below), but grub2 is supposed to fully support it, and definitely CAN install in the UEFI reserved partition. Several years ago I converted to gpt based partitions, which are native to (U)EFI but can be used on BIOS as well, if the kernel and boot-loader are compatible. Gentoo's grub1 (0.97-rX) has a patch that supports gpt, but it's definitely a hack as despite gpt having partition-types specifically reserved for both EFI and BIOS boot areas, grub1 is simply not designed to use them and continues to install its stage-1.5/2 to either the pre-partition space (if there's room) or into a partition. Still, back when I first switched to gpt, I setup both the reserved BIOS and EFI-system partitions, thus ensuring forward compatibility without having to repartition once again. Then sometime later, I upgraded to grub2 on my main system (not the netbook yet, I actually wait years between upgrades on it sometimes), which as I said, is fully gpt and efi compatible. Both systems are still legacy BIOS based, but are on gpt with both a BIOS-reserved and an EFI- system-reserved partition setup, as I said, for forward compatibility. Installing grub2 was therefore dead easy, because I already had the BIOS- reserved partition for it to use and it did so, altho learning the differences from grub1 and getting the vastly more flexible grub2 configured the way I wanted, taking advantage of all that new flexibility, did take some work. Meanwhile, I took advantage of the fact that I had multiple disks installed (at the time in kernel/md-raid1, now upgraded to a pair of SSDs in btrfs-raid1 mode), with separate boot configurations, to upgrade one of the disks' boot-loaders and /boot to grub2 and experiment with that, while the other one remained strictly off limits as grub1, until I was thru experimenting and 100% comfortable with grub2. Only THEN, with grub2 already up and working to my satisfaction on the first upgrade, did I touch the grub1 installation on the other drive, upgrading it to match, thus providing a backup boot option all the way from both grub1, thru one each grub1 and grub2, to both grub2, in case the one I was working with failed for whatever reason. So now I'm definitely a grub2 booster, as well as a gpt booster (it's FAR more reliable, with partition data checksumming and a second partition table in case the first goes bad), and don't intend to go back. The only reason I've not updated the netbook to grub2 yet, is because I've not updated it AT ALL, since I did the grub2 upgrade on the main machine. But as I said, while I'm a gpt and a grub2 user, and know based on personal experience that it works with gpt in legacy mode, and based on my research for the upgrade but NOT personal experience, that it works with EFI, since I do NOT have that personal experience with grub2 in EFI mode, I can't really tell you how that works, only that it is supposed to work quite well indeed with (U)EFI, as UNLIKE grub1, it was actually designed with MBR/BIOS/GPT/(U)EFI all in mind. I also know that a big part of grub2's flexibility comes from the fact that it's fully modular, with all sorts of modules available for MBR/BIOS/ GPT/UEFI (both 32-bit and 64-bit EFI, actually) and more, plus all the filesystems support is modules, as well as most of the available commands, the graphics mode, etc. So given that UEFI is a standard with the specs available, it's no surprise that grub2 supports it, since that's just another module to add to the many it already has. Actually, that's the story with both btrfs and zfs support as well -- in grub2 they're just filesystem modules along with those for ext1/2/3, reiserfs, etc, so adding support is a simple matter of adding another module with that support. Tho I should mention that I don't do proprietary software such as MS Windows at all any more, so I'm not a reliable source on its GPT/EFI support but I can warn that I have read that at least one version (Vista?) detects that at install and will let you do either MBR/GPT then, but won't let you switch between them without a full reinstall. So anyway, assuming your MS install can handle it, since you have the opportunity now that you're running Debian on the external, I'd recommend switching to at least GPT if you haven't, and preferably grub2 while you're at it, tho that /will/ take some research. And when setting up the GPT, I'd recommend setting up both a legacy BIOS-reserved partition and an EFI-system partition, just to cover your bases. You can then install grub2 to either one or both, as you wish, and I think, could then at least in theory (I'm vague on how that works, since I've not done EFI personally at all) choose between them, since you have an EFI system and thus have that end covered. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman
