unintentional installation on floppy by installation floppy

unintentional installation on floppy by installation floppy

[forsyth]

>>(20 megs) of Plan9.  However, for some reason the Disk1 is setting itself 
>>up on the floppy instead of on the partition I left available for Plan9.  

this has been mentioned before and struck me as strange at the time,
until i saw it happen recently and realised what caused it.

the plan 9 installation diskette tries to install on itself because
it has tried to mount something on /n/c (which is on the diskette)
and failed.  unfortunately the directory /n/c has been left writable,
on the diskette, and the installation program proceeds
to write to it.  unsurprisingly it runs out of space.

there seem to be many possible causes for a failure to mount on /n/c.
for instance, the DOS file system doesn't begin the disc; or it starts the disc, but
the dos partition doesn't look quite right (yielding `unknown format' on mount).
the latter seemed to be true for windows 95 on a student's machine here,
but i haven't had a chance to investigate.  (it was also the June Beta copy of windows
95; i'll wait until he buys the real version, in case it changes again.)