grub boot problem with md

Kuba Ober kuba at
Mon Oct 29 12:35:24 CDT 2007

On Saturday 27 October 2007, Greg Vickers wrote:
> Hi Ben,
> Ben Scott wrote:
> > On 10/26/07, Greg Vickers <daehenoc at> wrote:
> >> I recently installed grub on sdb with the following commands:
> >> grub> device (hd0) /dev/sdb
> >> grub> root (hd0,1)
> >> grub> setup (hd0)
> >
> >   When installing GRUB and encountering problems, I find booting GRUB
> > from floppy often helps (I got this idea from the docs, so the
> > developers think so, too).  When you're running GRUB under Linux, it's
> > seeing things the way the kernel sees them, which isn't always the way
> > GRUB will see them when self-hosted.  Boot from floppy, and GRUB is
> > self-hosted and running in real-mode, exactly as it will be when it
> > boots from the MBR.
> >
> >   So pull the first hard disk and boot GRUB from floppy.  Thus, GRUB
> > will see exactly what it will see when it boots that way from the HD.
> >
> >   You only have to install GRUB once, so it's usually not a big
> > annoyance.
> Thanks for the tip - so grub may see the disk that is plugged into the
> sata1 port (i.e. the second HDD) slightly differently as when that disk
> is presented by the kernel.

In fact, all grub can do is to guess as to the mapping between the two. 
Controller BIOSs can be disabled, etc, and it's just impossible to know which 
of the BIOS disks the particular linux device is gonna be.

For me, the "guessing" of the mapping has never worked. The only grub 
installation procedure for me, which works, is to install the grub rpm, then 
boot from a grub floppy/cd/usb stick and do setup (hdX), usually (hd0).

I have always had problems with using grub-install, whether on systems with 
SCSI cards, or add-in PATA/SATA cards, or hardware RAID.

Cheers, Kuba

More information about the Linux-PowerEdge mailing list