I have a new computer with Windows 8.1 and have gone to work at dual-booting with Ubuntu 12.04.3. I can boot Windows 8 from the grub menu just fine, and Ubuntu appears on the menu and I can select it, but it will remain on a blank screen, same color as the grub menu, and does nothing, no error message. However, if I put my Ubuntu DVD in the disk drive before starting up, I can select Ubuntu from the grub menu and it always starts up perfectly.

One thing I noticed is that if the disk is NOT in the drive, I see a little message "efi disk read error" appear several times just before the grub menu is displayed. The message does not appear if the disk has been inserted. Could someone let me know what's going on?

Additional details:

Just following my Ubuntu install, the initial problem had been that Windows was not recognized and didn't show up in grub. I ran boot-repair (results) from my Ubuntu installation (BIOS would not boot from the optical drive after installing Ubuntu). Following this, it appeared that everything was fine - I could boot Windows and Ubuntu, and I couldn't tell you whether it was because a disk was in or not. I didn't take note of this at the time.

After this I did some various installing of software on Windows, and also got the grub menu customizer on Ubuntu to shift around my menu options, and shove some ones I don't plan to use much into folders. But that's all. And this morning I noticed that I could not boot Ubuntu unless the disk was in the drive.


Concerning the "efi disk read error" message, I think you need to disable the Windows "Fast Startup" feature, as described here:

Doing so will not fix your more important "black screen" problem, but this problem is at least as serious in the long term, since failing to address it can result in filesystem corruption and, in extreme cases, an inability to boot the computer at all.

The "black screen" problem is a known one, but there are numerous different causes and solutions. The most general solution seems to be to use the nomodeset kernel option, but there are several others, many of which are unique to particular chipsets. Searching this site reveals several questions on this topic, such as:

I can't promise that any of these (or numerous others here or elsewhere) will help you, but I recommend you start with these answers.

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It looks like boot repair ran its "buggy" UEFI rename function. I am not sure it is always required, but it is for those UEFI that internally hard code UEFI to only boot the Windows efi file. So Boot-Repair renames the Windows file and makes grub2's shim be the Windows file. The UEFI thinks it is booting Windows but is really booting grub2/shim and then from grub2 menu you can boot Windows.

buggy-kernel detected. Do you want to activate [Backup and rename Windows EFI files]? yes (if any choice fails, please retry with the other)

Then renamed /EFI/microsoft/boot/shimx64.efi to bootmgfw.efi Actual Windows boot file, originally bootmgfw.efi, becomes this:


With the renamed file you cannot directly boot Windows from UEFI menu as it really is shim. And a Windows update may rewrite the bootmgfw.efi file overwriting the shim version, so then if you can only boot the Windows version you have to rerun boot repair. If you can boot Ubuntu entry in UEFI menu, undo the rename.

To undo & to rename files to their original names, you just need to tick the "Restore EFI backups" option of Boot-Repair. Windows UEFI install should have backup of bootmgfw.efi here:

C:\Windows\Boot\EFI\bootmgfw.efi from a working Windows x86_64 installation.

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