Re: Grub doesn't offer menu

On 20 May, 15:46, Ian <ian.gro...@xxxxxxxxxxxxxx> wrote:
On 19 May, 21:11, Martin Gregorie <mar...@xxxxxxxxxxxxxxxxxxx> wrote:

Ian wrote:
The working version of GRUB (for dapper) has root = /dev/hda7 in
it ...
Looks like the Feisty installer may have got it wrong. This could well
help to explain why Feisty doesn't boot.

The one with root=/dev/hda7 does boot just fine!

Are you sure that the Feisty boot partition is someplace where the BIOS
can find it, i.e. not too far from the start of a large disk? Don't
forget that GRUB uses the BIOS for disk access and if the BIOS can't see
the partition than GRUB can't either.

I tried find menu.lst and got a rude message saying that the BIOS
wouldn't allow access to the cylinders requested. Combined with the
damaged predesktop area, I strongly suspect that the Feisty installer
has managed to write GRUB into the hidden area of the disk.

Oh well, All I have to do is persuade IBM/Lenovo to sell me the system
restore CD's ...

Ian

Hold your horses a little, Ian.

Normally the 'predesktop area' you refer to is in fact a 'hidden'
partition. It may possibly be resurrectable.

I'd suggest using a partition editor in readonly mode to check you
have all the partitions you expect, and in the places you expect.

To quote from the GRUB manual " GRUB uses a special syntax for
specifying disk drives which can be accessed by BIOS.
Because of BIOS limitations, GRUB cannot distinguish between IDE,
ESDI, SCSI, or others.
You must know yourself which BIOS device is equivalent to which OS
device. Normally,
that will be clear if you see the files in a device or use the command
find"
GRUB refers to disks using a specila nomenclature - *all* fixed disks
are designated as 'hd', whether they are scsi or sata or whatever.
(hd0,0) is the first partition on the first disk; (hd0,6) is the
seventh partition on the first disk; (hd2,3) is the fourth partition
on the third disk.

Also "How to specify devices
The device syntax is like this:
(device[,part-num][,bsd-subpart-letter])
'[]' means the parameter is optional. device should be either 'fd' or
'hd' followed
by a digit, like 'fd0'. But you can also set device to a hexadecimal
or a decimal number
which is a BIOS drive number, so the following are equivalent:
(hd0)
(0x80)
(128)
part-num represents the partition number of device, starting from zero
for primary
partitions and from four for extended partitions, and bsd-subpart-
letter represents the BSD
disklabel subpartition, such as 'a' or 'e'.
A shortcut for specifying BSD subpartitions is (device,bsd-subpart-
letter), in
this case, GRUB searches for the first PC partition containing a BSD
disklabel, then finds
the subpartition bsd-subpart-letter. Here is an example:
(hd0,a)
The syntax '(hd0)' represents using the entire disk (or the MBR when
installing
GRUB), while the syntax '(hd0,0)' represents using the first partition
of the disk (or the
boot sector of the partition when installing GRUB).
If you enabled the network support, the special drive, '(nd)', is also
available. Before
using the network drive, you must initialize the network. See Chapter
6 [Network], page 21,
for more information.
If you boot GRUB from a CD-ROM, '(cd)' is available."

This URL expands upon the above:

<URL:http://www.gnu.org/software/grub/manual/grub.html.gz#Naming-
convention>

This URL may also help:

<URL:http://ubuntuguide.org/wiki/Ubuntu:Feisty/BootMenu>

Quite why booting works when using the wrong nomenclature, I couldn't
say.

You might ant to try the GRUB 'rootnoverify' command:

<URL:http://www.gnu.org/software/grub/manual/
grub.html.gz#rootnoverify>

As one of the other responders points out, the partition you are using
for the Feisty install may be on a portion of the disk that cannot be
accessed via the BIOS, so GRUB can;t see it. Some people have a
'boot' partition in the early part of the disk to get round this.

There is no particular reason why you can't have a separate instance
of GRUB for each partition, it's just that most people don't do that.

So, I'd suggest checking that your MBR is as you expect, and your
partition table is as you expect. Check if you are affected by the
BIOS disk addressing limitations, and ensure the nomenclature for your
partition ids in menu.lst is correct.

I've had fun and games trying to get GRUB to work as the GRUB device
names don't have a guaranteed one-to-one correspondence with linux
device names. Also, just booting with a USB drive inserted can mix up
the order of devices and cause a boot failure, as the USB drive could
be regarded as hd0.

I hope you can sort this out without resorting to a reinstall CD.

Sid

.

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