[lug] Cylinders and pertitioning

D. Stimits stimits at idcomm.com
Fri Nov 10 12:12:22 MST 2000

John Starkey wrote:
> I'm installing a 20 gig drive that I'd originally used for solaris. The
> drive is set for 2491 cylinders  and I'm trying to get it back to 1024.
> Can anyone tell me how to do this? I used fdisk and set it for 1024 but it
> won't write that setting.    I'd think that merely setting the cylinder
> count would throw off some other setting but I'm not sure how this all
> balances out.
> Thanks,
> John
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Long ago, before LBA mode existed (try LBA mode first), and the limit
was reached around 540 MB, once could lie to the bios by telling it you
had more heads (multiply in powers of 2) and fewer cylinders (divide in
powers of 2), but always keeping sector size the same. Then at bootup,
you had to pass the real geometry to the linux kernel. Lilo and the bios
were perfectly happy with lies, so long as cylinders x heads remained
approximately constant, and never higher. When the kernel takes over
after lilo, it needs its own, real knowledge of geometry.

I don't know if a modern bios will let you get away with that, but it
might. It is unlikely you can run (or need) LBA mode if this is done.

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