[HECnet] 'rexec' or 'ssh <command>' over DECNET

[Johnny Billquist]

On 2012-08-15 14:53, Paul_Koning at Dell.com wrote:

On Aug 15, 2012, at 5:05 AM, Johnny Billquist wrote:

On 2012-08-15 10:57, Sampsa Laine wrote:
Yes, I was aware of the batch submission, but wanted to do it the "ssh way" for a particular reason..

Ok. Note, however, that the solution you came up with now is not really generally usable in DECnet, but is rather VMS-specific. But on the other hand, more or less any solution will be rather specific...

The details are, but the general mechanism is common.   See the Session Control layer specification. Basically, server application addresses come in two forms (three, maybe, but the third doesn't really make sense) -- a name, or a number.   For example, FAL is number 17.

Right.
This is a named task object. The basic idea carries across, but for RSX, for instance, the named object must be an installed task name, and is not a file name.

That part is standardized, and the object numbers are registered (though no names are).   What isn't standard is how those session control requests are mapped to operating system objects or actions.

Yes. Which is why I made my comments that not only was Sampsas solution VMS-specific, but any solution will be rather specific...

For example, in RSTS (DECnet/E), incoming connections can go to already running programs that have registered the object name and/or number.   If there isn't one, the request is looked up in a database set by NCP which defines the mapping from name or number to a program.   Unlike VMS, there is no default rule that a name maps to that same string as an executable file.   But what Sampsa did could be done to a RSTS node so long as there is a session control database entry that maps that task name to the script file as the thing to execute.

In RSX, you have a database for numbered objects to specific task names. Object 0 is special, just like in VMS, in that you then give a name, and that name is outside the scope of DECnet. For RSX, the name is searched in the installed task list of the OS, while for VMS, it is assumed to be a filename in a specific directory.

For both numbered and named objects, the task does not have to be running in RSX. DECnet will activate the task if it isn't running. But it must be a task known to the system, or else it fails. And you have a database of mappings for numbered objects to which task to run.

	Johnny