Bootloader Error 18

Bjørn Ingmar Berg bjorn.ingmar.berg at gmail.com
Mon Aug 8 09:52:19 UTC 2005


On 08/08/05, Slabber A <14565471 at sun.ac.za> <14565471 at sun.ac.za> wrote:
> Hi, I installed Ubuntu 5.04 and when the installation was finish and my PC rebooted it said:
> "GRUB loading stage 1.5 "
> "GRUB loading pleas wait."
> "Error 18"

>From http://wiki.linuxquestions.org/wiki/GRUB :

Error 18: Selected cylinder exceeds maximum supported by BIOS
This error is returned when a read is attempted at a linear block
address beyond the end of the BIOS translated area. This generally
happens if your disk is larger than the BIOS can handle (512MB for
(E)IDE disks on older machines or larger than 8GB on others.). In more
practical terms this means the BIOS is unable to start executing the
kernel because the kernel is not located within the block it can
access at boot up time.

This can be circumvented by creating a boot partition at the beginning
of the disk that is completely within the first 1023 cylinders of the
harddrive. This partition will contain the kernel.

The kernel it self does not suffer from the same limitations as the
BIOS so after the BIOS has loaded the kernel the kernel will have no
problem accessing the whole harddrive. Newer BIOSes will automatically
translate the harddrives size in a way that it can be completely
contained within the first 1023 cylinders and hence modern computers
do not suffer from this problem.
The same error can happen when the BIOS detects a disk in a different
way as Linux does. This can happen when changing motherboards or when
moving a GRUB-bootable disk from one computer to another. If this
happens, just boot with a GRUB floppy, read the C/H/S numbers from the
existing partition table and manually edit the BIOS numbers to match.


Regards,
Bjørn Ingmar Berg




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