Its not possible to access the GRUB command line until stage 2 loads.
The CLI lives in stage 2.

----- Original Message ----- 
From: "Ken Teh" <[log in to unmask]>
To: "John Summerfield" <[log in to unmask]>
Cc: "Scientific Linux" <[log in to unmask]>
Sent: Tuesday, January 08, 2008 11:44 AM
Subject: Re: grub hangs with attached scsi disk


> John Summerfield wrote:
>> Troy Dawson wrote:
>>> Ken Teh wrote:
>>>> I just installed a 4.5 machine and it hangs when booting at "grub
>>>> loading stage 2".  Here's the strange part.  It hangs only when a SCSI
>>>> disk (LVD/SE) disk is attached.  SCSI card is an Adaptec 29160.  When
>>>> the  disk is removed, it rips right through the boot.  The disk is fine
>>>> because I use the 4.5 install disk in rescue mode and I can see the
>>>> disk, mount it, and all its data is there.  I tried with another disk
>>>> and I have the exact same result.  I'm baffled!!
>>>>
>>>> Ken
>>>
>>> The odd's are that it's because the disks are getting re-ordered when 
>>> you plug in and unplug the scsi disks.
>>>
>>> Without any disks there, grub is saying "here is my disk on (hd0,0) and 
>>> away I go"  And since hd0,0 is the right disk, away it goes.
>>>
>>> With the other disks there grub is saying "Well, I have two disks, 
>>> (hd0,0) and (hd1,0).  I'm told I need to boot off (hd0,0) and away I go" 
>>> But, in reality, your main system disk is what grub thinks is (hd1,0) 
>>> and so it's booting off the wrong disk.
>>
>> Ken, you can test this by getting to the grub command  line and typing 
>> stuff like
>> help
>> root (hd0,0)
>> root (hd1,0)
>> find
>>
>> etc etc
>>
>>
>
> Thanks to John and Troy who responded.  Unfortunately, I was not able to 
> resolve it.  I've reinstalled grub after specifying grub's root.  When I 
> do this, it hangs at stage 1.5 instead of 2.  I've verified it's the 
> correct root by 'finding' the stage# files. I've tried fixing the order 
> after reprobing and then editing the device.map file.  I've disabled SCSI 
> boot from the BIOS and verified that the BIOS boot order corresponds to 
> the device.map order.  I've even tried installing the machine without the 
> SCSI card so that the SL installer does not load the AIC7xxx driver.  All 
> to no avail.  I'm pretty sure it's something in grub.  The system was 
> running SL3.x with an IDE system disk and this external SCSI drive.  All I 
> did was reinstall it with SL4.5.
>
> Do you know if it's possible to get to the grub console at bootup but 
> before it loads stage 1.5 or stage 2?  If it is reordering, then I need a 
> "live" (or in this case, "dead") system to verify instead of booting 
> succesfully via linux rescue, then grubbing the system.
>