"grub rescue > " did not mean that grub needed to be fixed !

[smile4yourself]

adventures in Kubuntu ... Mar. 2013
Asus 99X79 Deluxe, i7 8-core cpu, 16 Gig mem.
using Asus boot menu in UEFI Bios to select which boot drive to use.
Win7 is on a separate drive.
--------------------------------------------------------------

a few days ago, I could no longer boot up into Kubuntu.

It looked as if Grub2 had been corrupted, because every time I would try to boot into Kubuntu, I'd get this prompt:


error: unknown filesystem.
grub rescue > _

I tried to reload kubuntu numerous times over the last two days, without much success. I had found some ubuntu pages with a boot_repair procedure, and tried this twice using different versions of Kubuntu live, but this would not fix the problem with the grub rescue menu... The only thing that seemed to work sometimes was reloading the OS completely from new. In one of these attempts I loaded Kubuntu 13.04 amd-64, and while it worked, it I also discovered that depending how I used the Asus boot manager, I could boot into the OS if I clicked on the boot menu prepended with "UEFI", but if I used another icon for the same drive that did not have "UEFI" I would end up with what looked like the broken grub menu. I could also get the same results from the Asus boot menu inside the UEFI screen.

Once the bootup has failed, the motherboard seems to want to continue to use the bad settings, so I found that clearing the RTC RAM (pressing a push button switch on the motherboard) sets the motherboard to a default state so it looks at the drives without the history of failures or successes. At this point I'm not sure what the settings do as they are not described in the motherboard manual, but the procedure that seems to work is:

1. from the boot menu in UEFI bios, click the Kubuntu drive starting with "UEFI:"

2. if you get the grub menu, reset the motherboard by pressing the RTC RAM switch and try "1" again.

What is important is that if you get the grub rescue > menu, do not assume that you have to fix grub. It simply may be what you pressed in the Asus boot menu.


I reloaded Kubuntu 12.04 amd-64 DVD, and am currently updating this page from Firefox running on that OS.

Has anyone seen this kind of problem and do you have any advice on the best way to set up Asus UEFI bios? I have not contacted Asus yet, but their manual is sparse on the topic.

Thanks for your help.

[Detonate]

I wish there was a dedicated forum someplace that discussed UEFI and Linux. If you do a search, you will find information spread all over the web about UEFI issues and Linux. If there was one place where you could go where Linux UEFI problems and solutions are discussed.

[Snowhog]

There is, right here. SteveRiley started the UEFI assistance board.

[Detonate]

Yes, I am aware of Steve's great post, but I was thinking of someplace that covered all distros and could be a "goto" place for any UEFI/Linux questions and answers and possibly include a hardware list of computers an MB's that users have tested. If I do a Google on UEFI Linux problem I get 409,352 hits. And Steve's post is not listed in the first 10 pages. Of course a knowledgeable user of search engines could boil that down, but even then there is going to be a lot of information to have to wade through and it is going to be scattered all over the web.

Those of us who are lucky enough to be members of this forum have a resource.

[SteveRiley]

I also discovered that depending how I used the Asus boot manager, I could boot into the OS if I clicked on the boot menu prepended with "UEFI", but if I used another icon for the same drive that did not have "UEFI" I would end up with what looked like the broken grub menu. I could also get the same results from the Asus boot menu inside the UEFI screen.

On machines with UEFI (not BIOS) firmware, the boot interrupt key (it's F12 on my ThinkPads) starts the UEFI boot manager. The boot manager will list:

* Each UEFI NVRAM variable that points to an EFI boot loader (the binary image that starts an operating system)
* Any FAT16/32 volume that contains the file \EFI\boot\bootx64.efi
* Any bootable volume that contains a "standard" boot loader

My T520 contains the following:

steve@t520:~$ [B]ll -R /boot/efi/EFI[/B]
/boot/efi/EFI:
total 20
drwxr-xr-x 4 root root 4096 Sep 29 13:15 ./
drwxr-xr-x 3 root root 4096 Dec 31  1969 ../
-rwxr-xr-x 1 root root  334 Mar  8 16:31 addbootvar.sh*
drwxr-xr-x 2 root root 4096 May 19  2012 boot/
drwxr-xr-x 2 root root 4096 Mar  8 17:36 ubuntu/

/boot/efi/EFI/boot:
total 756
drwxr-xr-x 2 root root   4096 May 19  2012 ./
drwxr-xr-x 4 root root   4096 Sep 29 13:15 ../
-rwxr-xr-x 1 root root 763360 May 19  2012 bootx64.efi*

/boot/efi/EFI/ubuntu:
total 45492
drwxr-xr-x 2 root root     4096 Mar  8 17:36 ./
drwxr-xr-x 4 root root     4096 Sep 29 13:15 ../
-rwxr-xr-x 1 root root 17940258 Mar  8 16:20 initrd.img-3.5-generic*
-rwxr-xr-x 1 root root 18075146 Mar  8 17:11 initrd.img-3.8-mainline*
-rwxr-xr-x 1 root root  5125712 Mar  8 16:01 vmlinuz-3.5-generic.efi*
-rwxr-xr-x 1 root root  5427472 Mar  8 17:11 vmlinuz-3.8-mainline.efi*

When I start the computer and press F12, I can select four items:

* Ubuntu with kernel 3.8
* Ubuntu with kernel 3.5
* Ubuntu with kernel 3.5 in recovery mode
* The model name/number of my computer's disk drive

The first three items appear in the list because they have corresponding entries in my UEFI's NVRAM variables. The fourth item exists because the UEFI boot manager found the file \EFI\boot\bootx64.efi on my FAT32 volume (which, in my case, is /dev/sda1). This file exists because my normal habit now is to place the EFI Shell on every computer I own. This is a handy tool to have around.

Bootable installation media for current Windows and most Linux distros is now constructed so that it will boot on machines that have either UEFI or BIOS. If you have UEFI and you have not enabled BIOS compatibility mode (or "compatibility service module" or "CSM"), then the computer will boot in UEFI mode and will load the file \EFI\boot\bootx64.efi. If you have enabled CSM, the computer will boot in BIOS mode and will load the MBR from the media. If you have regular BIOS, the computer will load the MBR from the media.

If a drive happens to have both an MBR and a \EFI\boot\bootx64.efi, then you can detect this if you press your compter's boot interrupt key. The boot manager will list both choices. The choice with "UEFI" in front will start the computer in UEFI mode with the EFI boot loader. The choice without the "UEFI" in front will start the computer in BIOS mode with the MBR.

[smile4yourself]

After working on trying to understand the Asus UEFI Bios boot option, I offer you here my findings:

http://kubuntufun.blogspot.ca/2013/0...t-options.html

while the motherboard works fine with Kubuntu, the boot menu leaves some room for improvement. I have not been able to duplicate the grub error that sent me off trying to fix grub, but I have not had to reset the RTC RAM either. The board sometimes remembers that the last boot was Kubuntu 13.10 and goes there directly without presenting the grub menu. At other times the grub menu is presented first. It must be something I'm doing. <smile> I contacted ASUS, but it seems they do not have information on how to set the board to boot Linux.