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Re: Re: Grub2 on UEFI

From: Michal Suchanek
Subject: Re: Re: Grub2 on UEFI
Date: Fri, 29 Jan 2010 21:51:38 +0100

On 29 January 2010 19:45,  <address@hidden> wrote:

>>  >
>>  >
>>  >
>>  > ?????????????????? If it possible to exit grub with EFI ERROR to process 
>> loading the
>>  > next loader?
>>  >
>>  > Exiting grub is in itself an error, an OS loader should never end.
>>  > So look for some quit command.
>> Why? I think it was in old BIOS times. EFI was a boot order concept, in one 
>> loader is failed, another
>> one is trying to boot.
>> If the boot loader exited it has obviously not loaded any OS hence it
>> has failed.
> Here I disagree. In old BIOS times we got only one try to load OS - the MBR 
> got the jump to the loader (lilo, grub, ntldr, whatever), and if the loader 
> fail - the whole booting it failed (however loader can "pass" execution to 
> another loader)
> Now, EFI has the concept or order  of loaders. The EFI firmware loader has a 
> list of loaders, if the first one (say grub) is failed, it will try next one 
> (say Windows Boot Manager). So, Windows Boot Manager is executed by EFI 
> Firmware loader, not by the grub>

Yes, you said it yourself - if it has failed. So any time the loader
exits it is a failure.

>> ·         What about  device names in grub2 for EFI? The problem  is that
>> old device names were based on BIOS device names, and it seems that in EFI
>> it's not the same. For example, what disk is hd0?
>> Unfortunately, the disk order is firmware specific and nothing can be
>> done about that. You should look at disk content or use UUIDs.
> Please, I need more info on it =)
> How can I identify the disk using disk content or UUID.
> For example, I got my kernel on NTFS partition and now smth like
> (hd2,1)/Loader/Kernel/vmlinux
> is written in grub config. Imagine that new disk is inserted oor new 
> partition is created, the booting will fail. For example I need to examine 
> all partitions and if one has a dir structure /Loader/Kernel/vmlinux and/or 
> UUID ... - load the kernel. How can I do that? I can't find mych information 
> on the topic

You probably want the search command.

The Debian scripts produce something like this:

search --no-floppy --fs-uuid --set <some long string of
numbers,letters and dashes here>

In GNU/Linux (with modern udev) you get can see the UUID mapping in

Disk check tools also typically report it.

If you use MS tools it might be named and formatted slightly
differently, though.



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