Red Hat Bugzilla – Bug 830123
RFE: add some documentation about GRUB2 on EFI systems
Last modified: 2016-05-19 15:33:49 EDT
The documentation for GRUB2 with EFI is very poor. I spent a few hours trying to figure out how it actually works. And it took me very long time until I configured the system to boot autonomously without my help.
It would be nice, if some basic information about grub2-efi can be included in the documentation for Fedora 18. I was told, that grub-efi is used in F17 because there are still some problems with grub2-efi.
I tried with grub2-efi-2.0-0.36.beta6.fc17.x86_64, and some stuff will probably change in future, but here are some points we could include:
- As EFI systems use EFI System Partition (ESP) to store bootloader images, the GRUB2 installation means copying the boot image on the partition. No MBR modification and similar is required. In case of Fedora, ESP parition is mounted to /boot/efi.
- You need to set up grub image to be used when booting. EFI systems provide some configuration tool when starting the system. This can be also achieved using "bootmgr" tool (not sure) and probably grub2-efi-install can do that (not sure even more). By default, the image location is "/boot/efi/EFI/fedora/grubx64.efi" and therefore the boot option in EFI boot manager is "fedora".
- Functional GRUB EFI image is provided in grub2-efi package. And it just works. grub2-efi-install probably selects different modules when building the image. I was able to boot with this image, but without grub menu. I do not know if I did something wrong, or if the tool should be invoked with some special options.
- Nice way to determine the expected location of grub.conf is to take a look at the target of "/etc/grub2-efi.cfg" symlink.
- To regenerate the GRUB2 configuration file invoke grub2-mkconfig like this:
grub2-mkconfig -o $(readlink -f /etc/grub2-efi.cfg)
Not sure, who can provide more information. I know that Mathew Garrett works on EFI and he probably knows a lot about the low level stuff. And Peter Jones (grub2 maintainer) as well. I'm adding them to CC, maybe they will have some other useful information.
I'm willing to help if needed. :)
Thank you very much for taking the time to report this issue, Jan.
Stephen has been working on this area.
I am sorry I was not aware of this bug before.
For the current state see the "Working with the GRUB 2 Boot Loader" chapter here: http://docs.fedoraproject.org/en-US/Fedora/21/html/System_Administrators_Guide/ch-Working_with_the_GRUB_2_Boot_Loader.html
there are few fixes in the master docs repo and some more coming in tie for Fedora 22
Please see: http://docs.fedoraproject.org/en-US/Fedora/22/html/System_Administrators_Guide/ch-Working_with_the_GRUB_2_Boot_Loader.html
Have you had time to review the docs as per comment 5?
Here is the new link: