[HECnet] Automatic Orderly Shutdown of Emulated VAX/VMS System in SIMH

[G.]

On Sun, 10 Jun 2018 13:00:39 -0700, Mark J. Blair wrote:

> It's easy enough to set up the host server to automatically launch a SIMH 
> emulation at boot time, but I don't know yet how to deal with automatically 
> and cleanly shutting down the emulation when the host server needs to shut 
> down. In particular, I'd want to somehow trigger an orderly VMS shutdown 
> when the host server needs to perform an unattended shutdown, such as when 
> the UPS signals a power failure. If there's a way to checkpoint the entire 
> emulation and then restore it later, that might also be a good option, as 
> long as I can prevent corrupting the emulated system's filesystems by 
> suddenly yanking the virtual power plug.

If you already have a working DECnet network between the Linux host and the
VMS guest, you could use the task-to-task feature to start a procedure which
would perform an orderly shutdown of VMS.

Look for dntask on the Linux side and make some experiments with something
simple like a directory listing. On the VMS side make sure that the TASK
object (number zero) is enabled in NETCONFIG, and that the called procedure
does define SYS$OUTPUT as SYS$NET and write something to it, because that's
the mechanism that triggers the connect confirm message to the remote node.

With this method it should be possible to even receive VMS shutdown messages
on Linux and then proceed accordingly (i.e. wait for the VMS shutdown or a
timeout before proceeding with the Linux shutdown).

HTH, :)
G.