Chaosnet shutdown service

[larsbrinkhoff]

There is a potential problem, especially with use cases like the PiDP-10, that people might turn off their computer without shutting down ITS cleanly. See e.g. #1683. FYI @ashkitten

Part of the problem is that it's difficult to automatically grab hold of the PDP-10 console teletype, log in, and execute the shutdown sequence. It's fraught with problems, e.g. what if someone is already using the console teletype.

One possible way would be to have a Chaosnet service to shut down. Of course, there's no guarantee that the network is up, or that the service will work 100% of the time. But it seems more likely to work than the console teletype. Making a host-side Chaosnet client should be easy enough.

I believe @eswenson1 did some work on forcibly logging out all users in order to shut down quickly.

[larsbrinkhoff]

Another way for the PiDP-10 case is to simulate toggling 37 to -1. See below ITS label ALCR6: SKIPGE 37 ;CHECK FOR PLANNED SYSTEM DEATH

[drboone]

Do the -10 sims have any support for powerfail actions?

[larsbrinkhoff]

I don't think they do. I have contemplated SIGPWR and mapping that to the power fail interrupt in the PDP-10. I don't think ITS handles the interrupt, although that could be changed.

[drboone]

Including SIGPWR would be elegant, but I'm betting that's not the signal that will arrive if someone shuts down the host machine without first shutting down the emulator(s).

[ams]

I would also welcome such a Chaosnet service, please add support for not just power-off / halt, but also cold boot and warm boot.

This would aid in remote CADRs on the Global Chaosnet.

[larsbrinkhoff]

Ok, the mode of shutting down could be e.g. a character: H for halt, C for cold boot, W for warm boot.

Another possible parameter is time, something like number of minutes to wait until shutting down.

I'm also considering some security token to restrict who can shut down.

[larsbrinkhoff]

Fixed by #2246.