grub error 18

kamkar1 · Nov 11, 2009

hi, I have a gateway single drive loaded with xp, and later loaded ubuntu 9.04. I have used linux op system for about 2 months and then I got the error:
GRUB ERROR 18,
I googled the error and they point to HD errors and the bios. So I changed the "large disk access mode" from "DOS" to "other" and I was able to boot up linux couple more times. Now I can't boot xp or linux. I am a newbie, with little to no experience.
any thoughts on how to correct this issue.

I have "live cd" ubunt 9.04 to access computer if necessary, but no xp boot disk

thanks
jk

BoredOutOfMyMind · Nov 11, 2009

I found this that you need a better definded /boot partition.

Ubuntu Forum Archives on Grub Error 18

Error 18

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 itself 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. If using a SUSE linux and installing on VM Ware this problem is solved by creating a small partition at the very beginning of the harddisc, and mounting it as /boot.
Error 18 on Dual Boot Systems Using a Single Hard Drive

This error often occurs when creating a dual boot system (with Windows) on a single hard disk drive, as in a notebook PC, because the Linux partitions end up being beyond the LBA range. On a large notebook drive you may need to re-install Windows into a smaller primary partition (or resize the partition), then create an extended partition in the unallocated space and create partitions for Linux Root, Linux Swap, and Linux Home, then in the remaining unallocated space create another NTFS partition for Windows. In other words, the Linux partitions must be immediately after the Primary Windows partition so they are still within the LBA range, then you can place additional NTFS or FAT32 partitions after the Linux partitions.

On a 160GB notebook drive, the following gave Error 18:

Primary: 80GB Windows NTFS

Extended: 4GB (FAT32), 50GB (NTFS), 4GB Linux Root (ext3), 2GB Linux Swap, 20GB Linux home (ext3).

The following worked:

Primary: 80GB Windows NTFS

Extended: 4GB Linux Root (ext3), 2GB Linux Swap, 20GB Linux home (ext3), 4GB (FAT32), 50GB (NTFS).

It can be somewhat of an annoyance to have the NTFS file system split into two partitions, but it's a workaround.

[Note: the reason for the 4GB FAT 32 partition is that it makes it possible for both Windows and Linux to access that partition, which can be useful when transferring files between the two operating systems.]

Read more: http://wiki.linuxquestions.org/wiki...ux.29_Using_a_Single_Hard_Drive#ixzz0WX2OhJMH
Click to expand...

kamkar1 · Nov 12, 2009

Thank you Boardoutofmymind for your reply.
I did some google search and found a couple of tricks using grub commands.
In any case, both my attempts to correct the grub were unsuccessful.
Finally reinstalled the Ubutu portion. After reboot both XP and ubuntu are functional.
Again, thank you for your support.

PS: one link that I thought was very helpfull for future reference is:
http://ubuntuforums.org/showthread.php?t=956276

regards,
jk

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