update-grub help

Dave Howorth dhoworth at mrc-lmb.cam.ac.uk
Wed Jun 2 15:24:55 UTC 2010

Tom H wrote:
> On Wed, Jun 2, 2010 at 9:44 AM, Goh Lip <g.lip at gmx.com> wrote:
>> On 06/02/2010 08:14 PM, Tom H wrote:
>>> On Wed, Jun 2, 2010 at 5:54 AM, Dave Howorth<dhoworth at mrc-lmb.cam.ac.uk>  wrote:
>>>> Tom H wrote (rearranged):
>> Tom, Dave, hope I am not interrupting your flow, if I may suggest couple
>> of things which may or may not work......
>> o When at ubuntu, type at terminal
>> sudo grub-install --recheck /dev/sda
>> If it doesn't help, at least it will do no harm.
>> o at terminal, type "sudo grub-emu"
>> then when grub emulation appears, do
>> grub> ls (hd5,1)
>> Suse is at sdf1, right?

Right sdf is opensuse, sdg is the 3ware BUT hd4 is 3ware, hd6 is opensuse

>> Since this is actually at ubuntu and not really at grub, it may list out
>> the output of the suse partition. If there is some output, Dave, please
>> write out this output.
>> Then we'll try to boot with this information.
>> To quit grub-emu, type 'exit'. Then at terminal type 'reset' to clear mess.
> No flow, no interruption!
> I'd forgotten about grub-emu. Good idea! It saves on rebooting to
> check whether an ls at the grub prompt shows all the disks and
> partitions.

Thanks for the suggestion, both of you, but I have two difficulties with

First is access to grub-emu. On another karmic machine:

$ grub-emu
The program 'grub-emu' is currently not installed.  To run 'grub-emu'
please ask your administrator to install the package 'grub-common'
grub-emu: command not found

but grub-common IS installed and when I list the files it includes, it
doesn't include grub-emu

Second is that I don't believe it will help :( grub-emu uses the host OS
to access devices and we know that Linux can access the disk. IMHO,
that's why the device.map files generated by both grub1 (opensuse) and
grub2 (ubuntu) include 7 devices and specifically include hd6. But an ls
command run from the grub command-line does NOT see hd6.

The problem as I see it is this ...

The BIOS can't see the opensuse disk; grub uses the BIOS to access the
disks, so it can't see the opensuse disk. I believe that until I break
this chain, there'll be no success. There are four ways I'm considering:

-1- use the grub2 ata module - after I insmod ata, the ls command can't
see any disks at all. The docs say that the ata module applies to SATA
disks in legacy mode but my disks are in native mode. So I'm stumped on
this approach.

-2- figure out a way to make the BIOS see the disk. I haven't found any
indication that a BIOS upgrade would help and I haven't found any hints
of other useful BIOS changes. So I'm stumped on this approach.

-3- reinstall opensuse to a partition on the 'ubuntu' disk. I think this
will work. The only question is whether being able to boot from the
other disk will be important to me at any future time, in which case I
would prefer to solve the issue now. So I'm considering this option.

-4- install grub1 instead of grub2. I haven't checked yet whether this
is even likely to help. So I'm researching this.

Cheers, Dave

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