Re: map'ping disks

[Carel Fellinger]

On Mon, Feb 26, 2001 at 07:43:41PM +0100, Thomas Krebs wrote:
> Hello grubbers,
> don't know if this is a bug but i have problems mapping disks with
> the map command.
> I have installed Linux and Solaris 8 on two different disks. I
> installed them both independently when each (SCSI) disk was set to
> disk 1 when installing. So the root Linux partition is on a filesystem
> mounted to /dev/sda1 and the Solaris root partition is mounted on
> /dev/c0t0d0. I want to be able to boot both of them with grub when one
> of those disks is set to disk 1 and one set to disk 2. As the filesystem
> entries are set as each disk was disk 1 I think I have to use the map
> command to let both OSes assume they are on the first disk.
> To accomplish that I do something like that:
> 
> map (hd0) (hd1)
> map (hd1) (hd0)
> kernel (hd0,0)/boot/vmlinuz-2.2.14 root=/dev/sda1
> 
> e.g. for Linux.
> But this does not work properly, i.e. linux boots but when it tries to
> access the filesystems it (apparently) accesses the partitions on the
> first (Solaris) disk.

I'm no grubber and I've hardly linux knowledge, but...

As I understand it map only influences the why the BIOS handles the
disks, but Linux doesn't rely on the BIOS for its disk access, so once
linux is loaded you'll have the real disk order again.  So make sure
your /etc/fstab points to the real disks, and don't assume they are
reordered with maps. The same for the kernel line in grub, don't use
mapped drives there. In my experience linux drives are easily reordered
as long as you adjust their /etc/fstab entries.

-- 
groetjes, carel