RE: error: no such disk

[Leslie Rhorer]

> The issue I'm still having, and still had when the suggested changes
> were made, is that grub says there is no such disk; I'm then presented
> with the grub rescue prompt and I'm unable to ls any of hard drives. I
> can, however, do an ls and see all the hard drives themselves, I just
> can't ls their contents. When I do an ls of any of the partitions I
> get an unknown file system error.
> 
> Could the insmod ext2 line be the cause? (hd1,4) is an ext4 partition,
> but the ext2 module is being loaded. I checked to see if I have an
> ext4 module: I don't. But this shouldn't matter because ext4 is
> backwards compatible with ext2.

        Well, there's "backwards-compatible", and there's "backwards
compatible".  I am not familiar with ext4, but it is entirely possible the
ext4 module can read ext2 partitions, but an ext2 module cannot read ext4
file systems.  If the failure you are getting happens after the Linux kernel
and initrd are loaded, then this sounds like an issue in the initrd image.
If this is the case, you might try updating the initrd image via whatever
method your distro employs.  If the failure is happening in the grub loader
before the Linux kernel is loaded, then it is an issue with grub.

> The issue I'm still having, and still had when the suggested changes
> were made, is that grub says there is no such disk; I'm then presented
> with the grub rescue prompt and I'm unable to ls any of hard drives. I
> can, however, do an ls and see all the hard drives themselves, I just
> can't ls their contents. When I do an ls of any of the partitions I
> get an unknown file system error.

        Um, OK.  That's a little convoluted, but I think I see what you are
saying.  If grub cannot read the file systems (ext4 or whatever), then it
can never see the structures allowing it to find the stage 1 loaders or the
Linux kernel, which may reside in /boot/grub, /grub, /boot, /, or whatever.
In my particular case, I have tiny ext2 partitions containing only the Linux
kernel and initrd files in / and the grub files in /grub.  Grub sees these
as simply / and /grub on /dev/md1 ( hd0,0 or hd1,0, as the case may be ).
Once the kernel is loaded and the md module is active, /dev/md2 (consisting
of hd0,1 and hd1,1) is mounted on / and then /dev/md1 is loaded on /boot.
The point is, grub must be able to recognize the file system where the
kernel and the grub files are found.  If the grub menu (menu.lst) comes us,
then grub is finding menu.lst, and it recognizes the boot partition at least
well enough to try to pass over control to the kernel.  If not, then in
order to fix the problem, you are going to have to provide grub with a file
system it does recognize.  Whether that file system can be ext4 or not, I
don't know.  That's one reason why I have a separate boot partition.  It
allows the boot file system to be as rudimentary and / or widely supported
as possible, while allowing the other file systems to be as new or have as
many bells and whistles as I want.