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Grub2 has disappeared (UEFI)
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doralsoral
Tux's lil' helper
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Joined: 12 May 2004
Posts: 118

PostPosted: Fri Jul 10, 2015 1:35 am    Post subject: Grub2 has disappeared (UEFI) Reply with quote

I have been dual booting windows 8.1 and gentoo for months via UEFI. Today i had an issue with an HD in another computer. To troubleshoot i unplugged my ssd from my main computer (This drive is the boot drive containing all windows/gentoo partitions). When i hooked it back up after troubleshooting the other drive grub seems to have disappeared. The only thing i can boot into is the windows bootloader which just loads windows. If i choose to boot from the actual drive it says it cant find the boot disk. I made no changes whatsoever to anything. Im going to guess that i don't understand UEFI enough to know what caused this. Does anyone have any insight?
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ian.au
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Joined: 07 Apr 2011
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Location: Australia

PostPosted: Fri Jul 10, 2015 3:44 am    Post subject: Reply with quote

Not much insight can be gleaned from the supplied info, really. *Edit: Sorry says grub2 in the subject, wish that could be seen when replying here :evil:

You unplugged the drive, attached another drive (type? reason? and booted it? into what? and it worked/failed/melted?) removed the second drive, reattached the first and no boot sector for grub on (assumed GPT due to win8) partition table, but some prior entry for windows? Too odd.

You say nothing was changed, but was the other hdd/ssd uefi boot too? If you swapped the bios to legacy and back on your drive2 mission, breakage will occur and reinstalling the bootloader is probably required (chroot back in and redo the handbook from installing the bootloader maybe?). Is the bios set correctly now? (I'm guessing so if win8 is booting) Secure boot not defaulted to on?

I can't think of anything else, and have no current (past xp) windows experience, so don't run anything similar.

If you boot into efi with system rescue cd can grub2-mkconfig -o /<path/to/grub.cfg> (assuming grub2) find the boot kernel? (I'd try that before reinstalling anything else) ;)
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doralsoral
Tux's lil' helper
Tux's lil' helper


Joined: 12 May 2004
Posts: 118

PostPosted: Fri Jul 10, 2015 12:55 pm    Post subject: Reply with quote

I ended up reinstalling grub and was able to get it back. I did not swap the bios back to legacy when troubleshooting the other drive but why would that break it? Also after getting grub back and booting back into gentoo X will no longer start using the nvidia drivers. Is this just a coincidence?
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ian.au
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Location: Australia

PostPosted: Fri Jul 10, 2015 1:06 pm    Post subject: Reply with quote

I think there are problems with nVidea drivers in 4.0.5 and some cards so I'd guess unrelated.

re swapping between uefi and legacy I read somewhere that some bios' are flaky when it comes to keeping track of the uefi settings between mode-changes. I can't recall exactly why. Glad you got it back.
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doralsoral
Tux's lil' helper
Tux's lil' helper


Joined: 12 May 2004
Posts: 118

PostPosted: Fri Jul 10, 2015 2:52 pm    Post subject: Reply with quote

Yeah I wish companies would come up with some standards of UEFI to keep headaches like these away. Also im still on 3.9. I havent booted into gentoo for like a week and havent updated any packages since then.
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ian.au
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Joined: 07 Apr 2011
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Location: Australia

PostPosted: Sat Jul 11, 2015 12:21 am    Post subject: Reply with quote

Yup, the black art of bootstrapping surely doesn't need extra hardware vendor 'features' :)

Sorry I really can't help with nVidia stuff. I got tired of jumping between the blob and nouveau to cope with code re-factoring there years ago, I just won't buy/install nVidia cards any more. Fortunately I only maintain systems that need basic business graphics capability these days.
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