Build successfully completed for simh emulator but emulator halts immediately on start

[jordanhubbard]

jkh@ubuntu-> ./start vt52 VT52 started, pid 3100

PDP-10 simulator Open SIMH V4.1-0 Current git commit id: 348f5f29 /home/jkh/Src/its/out/simh/boot-10> at -u dz0 10004 %SIM-INFO: Listening on port 10004 /home/jkh/Src/its/out/simh/boot-12> at -u dz0 line=7,10018 %SIM-INFO: Line 7 Listening on port 10018 /home/jkh/Src/its/out/simh/boot-14> at -u dz0 line=6,10019 %SIM-INFO: Line 6 Listening on port 10019 /home/jkh/Src/its/out/simh/boot-16> at rp0 out/simh/rp0.dsk %SIM-INFO: RP0: Unit is read only

HALT instruction, PC: 777721 (HALT 777721) sim>

Ubuntu 22.04 on x86_64 architecture

[larsbrinkhoff]

/home/jkh/Src/its/out/simh/boot-16> at rp0 out/simh/rp0.dsk %SIM-INFO: RP0: Unit is read only

This shouldn't happen. Why is the rp0.dsk file not writable?

[larsbrinkhoff]

I will speculate there might be a file permission or ownership problem.