[Simh] PDP11 UNIXv6 problem -- cannot find sources for the kernel

[Michał Mazurek]

i have downloaded the unixv6 images from simh's website, but i noticed that there is no /usr/sys
directory with source code for the kernel. i grep'ed unix1_v6_rk.dsk and found that they are present
somewhere there (files like filsys.h etc), but when i run find / -print in the emulator those files
are nonexistent. greping /dev/rk1 for parts of source code (like, say, s_ilock) shows me good
results. /etc/mount says that rk1 is mounted on /usr. but there is no /usr/sys, and i cannot find
the sources of the kernel (userland sources are present). the id32 port of unixv6 (also downloaded
from simh's website) has those sources present when run. i am booting the emulator as it is written
in the manual, running pdp11 as this:

set cpu u18
att rk0 unix0_v6_rk.dsk
att rk1 unix1_v6_rk.dsk
att rk2 unix2_v6_rk.dsk
att rk3 unix3_v6_rk.dsk
boot rk0

how can i make the pdp11 emulator program see /usr/sys?

-- 
michal