Turns out not linking my a.out was a bad idea; I fixed it by doing this: exit = 1. mount = 21. sys mount; rk0+040014; usr+040014 sys exit rk0: </dev/rk0\0> usr: </usr\0> This seems to work. I think the rk fs image is not right, but Warren seems to have a grip on that and I'll try his latest mkfs next. -brad