Re: getting grub's view of disk geometry from "grub rescue>" prompt?

[Nathan Stratton Treadway]

On Fri, Mar 15, 2019 at 19:43:18 +0100, Pascal Hambourg wrote:
> Le 15/03/2019 à 01:53, Nathan Stratton Treadway a écrit :
> >Question in brief: how can you get Grub, from the "grub recovery>"
> >prompt, to display its boot-time view of disk drive geometry, etc?
> 
> You can run 'ls' to print all detected disks and partitions, then
> run 'ls' with each disk or partition as argument to print its size,
> sector size, starting position...

Thanks, this sounds like part of what we're looking for... but what's
the exact syntax?

When we tried it, "ls" did give the list of detected partitions:

  grub rescue> ls
  (hd0) (hd0,msdos1)

, but doing ls on a partition only showed the filesystem type:

  grub rescue> ls (hd0,msdos1)
  (hd0,msdos1): Filesystem is ext2

Would it be "ls (hd0)" that would show the full partition table
information for the device?


Also, is there any way to determine which mode grub is actually using to
access the disk?


> As a workaround, you can try to create a small partition for /boot
> at the beginning of the card.

Yes, this is our plan... but we're trying to figure out what size the
partitition can safely be.  If the limit is large enough, we might
decide to split the partitions between "root" (medium sized) and "misc"
(the rest of the space), rather than very-tiny /boot and the rest as
the root... or something.

(Also, we have another machine, very similar to the first, where the
initial Debian installation to a single partition worked without a hitch
-- so now we are wondering if there is some subtle difference in the
boot-time environment between the two, or if the first time through we
just got lucky and the boot may start to fail in the future if new
versions of files in the /boot directory happen to get allocated farther
toward the end in the filesystem.  So it would be nice to know how to
find out directly from grub what the actual boot-time limits are....)

Thanks again for your help.

                                                Nathan

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