Red Hat Bugzilla – Bug 827579
grub2 fails when prep and /boot are on different disks
Last modified: 2013-01-20 11:33:58 EST
== Comment: #0 - Brent J. Baude <email@example.com> - 2012-06-01 15:04:31 ==
Grub2 is unable to read its menu file (grub.cfg) or kernel and initrds when the prep partition (where grub lives) and /boot are on different disk.
Consider the following scenario. A system with two disks. You install prep on disk 1 and on disk 2 you put /boot and /.
/dev/sda1 == prep
It will not be able to read the grub.cfg in /dev/sdb1 and drops to grub2 rescue prompt.
You can also trip into this scenario where multiple installations are present. Consider the following:
You install a Linux distro on a disk. (sda) and end up with
/dev/sda1 prep (with yaboot or grub2)
/dev/sda3 large lvm for / and swap
Then install Fedora (with grub) on a second disk:
/dev/sdb3 large lvm for / and swap
In this case, when you point SMS to boot from sdb, it will load the grub menu succesfully and present grub menus for Fedora and the other OS. The Fedora OS will boot fine. The other OS, though has a proper configuration within grub2, will not boot because grub2 cannot cross the disk boundary to load the kernel and initrd.
Here are some possible things we can consider:
1. remove 30_os_prober from ppc64 grub2, which only resolve the second scenario described.
2. set an OF alias so grub can traverse disks, though these have the downside of being deleted under certain circumstances.
3. alter grub to deal with OF device names?
Well it's funny to see this right after IBM has pushed to disable OFW tree traversing on IBM systems because it returns incomplete names (missing @X part) and attempting to open them causes IBM firmware to segfault. Supporting configurations like this needs either:
- A way to enumerate all drives on a computer. Do you have a spec on how to add those missing @X on IBM?
- A way to get OFW device name reliably from OS.
It preference we need both.
Vladimir: could you elaborate on the issues with IBM Fw or link to the relevent discussion? Thanks.
FWIW and without knowing anything about PPC: I have seen similar symptoms on EFI, caused by Fedora's grub-2.00-add-fw_path-search.patch hack.
------- Comment From firstname.lastname@example.org 2012-12-04 20:10 EDT-------
Thanks all. Closing as per previous comments. We'll open a Fedora 18 bug if we find a regression there.