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I have a ThinkPad X130e. I installed Ubuntu 12.04 LTS amd64 on it. All worked fine until yesterday. While diagnosing another issue I reset the BIOS / UEFI to defaults. Afterwards Ubuntu did not boot any more. The ThinkPad shows Operating System not found and that's it.

Did the BIOS / UEFI reset somehow nuke GRUB? If so how is that possible? How do I fix it?

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2 Answers 2

up vote 3 down vote accepted

A BIOS reset, voluntary or through an update will wipe the EFI boot entries more often than not.

To restore the boot entry one has to use a recovery disc and reinstall grub-efi or grub-efi-amd64. The entry can also be added manually.

This question shows a couple of ways to fix it: http://superuser.com/questions/376470/how-to-reinstall-grub2-efi.

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It's more likely that you switched a boot option from (U)EFI mode to BIOS mode or vice-versa. The two boot modes are entirely different, and if the firmware looks for one type of boot loader when it's not present but the other type is installed, you'll get an error like the one you described.

To fix this, I recommend you enter your firmware setup utility and look for any options that refer to "EFI", "UEFI", or "legacy boot". Once you've identified all such options, try to figure out which one is the best candidate for experimenting and change it.

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Thanks for the answer. However that's not the case. The default setting is UEFI. However I already found what the problem was. The ubuntu boot option is wiped once the firmware is reset. Afterwards it needs to be readded via the recovery option of the CD. –  lightrush May 21 '12 at 16:02

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