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