How Plan9 Buggered my dos partition.

How Plan9 Buggered my dos partition.

[David]

I brought my PC to run plan9, so I'm one of those fortunate people
who only uses DOS to play Doom. I can corrupt my DOS partition
with impunity. However this is how Plan9 buggered my DOS partition,
for those of you might want to avoid it.

I've started with a 1 gig IDE DOS drive and stuck on a 1/2 gig as 
drive one and did a floppy install on it thus sticking the plan9 
partition info on the 1/2 gig drive.

I then managed to get the CD out of Harcourt Brace (Don't ask how, 
it's difficult and you have to talk to someone who doesn't know what 
it is, so that they sell it to you before the HB thought police find 
out and stop the sale).

I then tried a full install on the 1/2 gig, but it wouldn't work 
because it wanted 6Mbytes more space before it would start 
installing.

So I repartitioned the 1/2 gig as a DOS drive, copied my DOS files 
onto and and swapped the drives around, installed Plan9 on the 1 gig 
and used the 1/2 gig as my boot disk (hd0).

Everything worked until I recompiled 9pcdisk to fix the keyboard 
mappings for a UK keyboard. The job was big enough to make the 
machine swap to disk when the linker kicked in. DOS went into a 
wobbly next time I rebooted. Something had splatted all over the 
directory and files.

'Why?' you may ask....

termrc contains a bit of script which check if a hd0 partition exists 
and tells plan9 to swap onto if it does. repartitioning the 1/2 gig 
drive didn't wipe the last sector which held the redundant plan9
partition info. So the default plan9 termrc finds a hd0 partition map 
along with a swap partition and swaps to it when you do a big 
compile. Oops...

The moral is: If plan9 is on hd1 and DOS is on hd0, be sure there 
isn't a plan9 partition table at the end of the DOS disk and edit 
your termrc file to swap on hd1.

David