On Sat Jan 7 13:30:33 EST 2012, tlaro...@polynum.com wrote: > Hello, > > Since I'm playing with the installation, I have been hit once again > with disk/fdisk corrupting the MBR and rendering other systems > unbootable. > > The explanation is arithmetic truncation. disk/fdisk.c does this: > > p->start = lba/sec2cyl; > > and, if modifications are done (for example creating a Plan9 partition, > of marking a primary partition active), when written back, the entries > are "restored" by: > > *endlba = (vlong)p->start*sec2cyl; > > Of course, if the values were not integer multiples of sec2cyl, the > entry point for the PBS is corrupt. (For example, on *BSD, the principle > is the same as for Plan9: a "primary" partition is a sequence of > adjacent bytes, furthermore subdivided; but one special subdivision > [a] is at the same offset (at start) and holds the bootcode and a > disklabel describing the subdivision; if the MBR is corrupt, neither > boot nor disklabel so user can conclude: everything lost). And the first > travel in the flying saucer will also be the last...
can you just set sec2cyl=1? - erik
