> You know, linux can use serial ports as a console device...  So why
> hasn't IBM come up with a virtual serial port type of console system
to
> use instead?  Something like having the console on /dev/ttyS0, and
that
> via some z/VM magic, is available on an IP as a port number.  Telnet
to
> the port, and Linux's getty takes it from there.  Or better yet,
through
> some z/VM magic, the serial ports could be mapped to another Linux
> host's serial ports, say one set up as a console appliance... Then
that
> appliance could be configured to allow access to them in a variety of
> ways, whether it be by port numbers, account names, ssh key, whatever.

Just thinking out loud, but: 

You could construct something like this using PVM fairly trivially,
assuming you were willing to tolerate a 3270 console on the Linuxen (and
that the 3270 console driver in Linux tolerates DIALed terminals coming
and going at the appropriate addresses in the virtual machine) and that
PVM was easily available on IFLs. PVM is astonishingly powerful for
doing stuff like this, and Endicott has fixed the licensing problem on
IFLs due to PVM being necessary for CSE. The PVM link signon protocol is
remarkably simple, and could easily be supported on Linux with a little
work.

You could probably also simulate this using YVETTE without spending any
money -- connect to VM, DIAL YVETTE, then DIAL to the guests as
appropriate. I'll have to try this out later. 

Wrt to your idea of a console server appliance, that could be done
fairly easily if you run telnetd on a nonstandard well-known port, and
then configure /etc/ttys to allow root logins on that set of ptys. Cisco
has a nice way of mapping serial links to hostnames in IOS that might be
a interesting model. The console appliance would need some type of
relatively secure solicitor as a login shell... hmm. I think this is
possible to do. How badly do you want it? 8-)

> I've been imagining this for a long time now, and just wondered why
IBM
> never did it.

I think this is how the Integrated ASCII Console thing is supposed to
work. 
It doesn't scale all that well, and with the line-mode support in the VM
TELNET server, it's really not all that necessary -- you can already get
a TTY console connection to use to get the network up, and then you can
get directly to the system in question w/o getting the VM system
involved at all. 

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