I recently installed netbsd-1.4.2 on an LC475 (with full 040) I just 
got, and I thought since the Mac installer makes an ffs of type 1 by 
default and newfs makes one of type 2, I should convert the root file 
system.  Though I wondered if I could safely do it in single user 
mode with / mounted read-only, I figured something would complain if 
the volume needed to be unmounted.  So in single user, I did this:

fsck -T ffs:"-c 2" /

which promptly core dumped.  Doing an fsck on the volume now produces 
the following error:

/dev/rsd0a: BAD SUPER BLOCK: VALUES IN SUPER BLOCK DISAGREE WITH 
THOSE IN FIRST ALTERNATE

and fsck can't do a thing about it, apparently.  At least I haven't 
found a way through reading the man pages to get fsck or fsck_ffs to 
fix it.  Do I really need to reformat the partition and start over? 
And is this a bug, or did I do something wrong?

--
Nathan Raymond