Old box, new install, Grub fails error 18

abo ulist at gs1.ubuntuforums.org
Fri May 20 20:53:16 UTC 2005

For the record, I experienced boot problems with both lilo and grub on a
Thinkpad T42p, which is not that old. Lilo was giving me "L 99 99
99...", and grub was giving me error 18.

It turns out the Thinkpad bios has an option to protect the special
4.5G setup non-partition at the end of the disk (Accessed under
"Security" options). When set to "normal" this hides the last 4.5G of
the disk. It seems Linux is not tricked by this, and sees the whole
disk, so LILO and grub get installed with the whole disk geometry.
However, when booting, LILO and grub use the BIOS, which reports the
fake geometry minus the 4.5G, causing both LILO and grub to barf.

Setting the bios setting to "disabled" makes the bios geometry match
the real geometry, allowing LILO or grub to boot.

Note: the "Free" 4.5G at the end of the disk that the debian-installer
partition tool shows you actually has the IBM Setup stuff. I have seen
some info that suggests on the T42p this is shown as a fat32 partition,
but on my system it showed as empty. You can overwrite this stuff, but
it means the IBM recover features (that basically does a fresh winXP
install from this partition) will not work. Search the web for info on
how this Setup data can be burned to 7 CD's so you can restore it later
if you want to.

Also, this bios option also has a "secure" option in addition to the
"normal" and "disabled" option. This claims to both hide and protect
the non-partition from modification. I suspect that Linux will bypass
this protection also, but it could cause other problems during
installation if it really did "protect" that area from writes.


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