Didier Kryn <kryn@???> wrote:

>    I don't understand all your explanations, sorry :-) . I understood the concept of "seat" as the combo you describe (graphics-keyboard-mouse).

>
> If the concept of "seat" includes serial terminals, I see no reason to not include remote logins: until the middle of the 80's, serial terminals could be far remote, by the means of modems, and, conceptually, this isn't different of a telnet connection. If multi-seat involves all that, then the concept is not relevant in this discussion. Which is relevant is wether the user can push the shutdown button of the DM or "send" ctrl-alt-del, and neither serial terminals, nor remote sessions can do that - except, possibly remote graphic sessions through XDMCP.

Yes, it is a bit of a side track, but the discussion is moving along with (as it appear to me) an implicit assumption that "multi seat" == "multiple graphics cards, keyboards, mice (KVM - Keyboard, Video, Mouse)". Taking a step back, this combination is just a subset of multi-seat.

Whether graphics or serial terminal (which did in fact often do graphics BTW) the principle is the same : A user "does something", that something gets signalled to the computer via it's cable, the computer "does something" with that input, and then sends some updated display information up the cable to the display device. The only real difference is that with a serial terminal the interface between the "user interface" and "the system" is via serial, with a KVM the interface is over the system's internal bus.*

To an extent, telnet and SSH are also a subset of this, though the mechanism is somewhat different.

A correction though. While a serial terminal typically cannot reset the system (other than via commands), it is perfectly possible to run a remote KVM which *CAN* do that. Just extend the KVM cables, and if they won't go far enough of you can't run the cables, convert to something intermediate (eg KVM over IP) very much like connecting a serial terminal via a modem.


What I struggle to understand is why "multiseat" as it's being discussed here (as an aside to the "can I shutdown from the login screen" discussion) should be considered so "hard". It's really (or shouldn't be) any different to (say) serial terminals - instantiate a "login process" for each instance of the hardware, "getty" on a serial line, choice of display manager (or whatever) for each KVM set.
Or have I missed something obvious ?


* As an aside, I recall reading many years ago that PCIe would allow the "PC" to be split up - with high speed serial links connecting the processing unit and the graphics card. It eventually arrived with Intel/Apple's Thunderbolt.
Get a Thunderbolt equipped system, plug multiple Thunderbolt displays into it, plug a keyboard and mouse into each screen. Hmm, looks very very much like a modern day serial terminal !