Re: Need "console switch" - any ideas?

[Jurgen Botz <jurgen@botz.org>]

John Geletej wrote:
> I find myself in need of a "box" that will allow several UNIX
> workstations/servers to be controlled at a single
> keyboard/mouse/monitor. My primary need is for SGI equipment, but I may
> need to incorporate a couple of Sun SPARCStations into the mix as well.

My preferred way of doing this is to use a serial console server, as
follows:

Stick a 32 or 64 port serial card into a PC (Cyclades makes good ones),
run Linux or *BSD on the PC, and install Paul Vixie's excellent rtty
package to serve up the serial ports (available from ftp.vix.com).

The advantage of this method over a "keyboard/monitor switch" is
obviously that you can get at the serial console remotely.  The
advantages of this method over a more simple terminal-server based
solution are:

1) More than one person can be connected to a console port at a time

2) Not only can you remotely connect to console ports, but everything
   that happens on them gets logged... this is a big one because not
   infrequently when something unusual happens to a machine the only
   information about it is written to the console, and can thus be lost
   if not logged.

3) You can make it very secure by allowing connections to the console
   server only via Ssh.  By using Ssh's feature of tying a particular
   command to a particular public key you can give out keys for specific
   consoles to specific operators without giving them access to all
   consoles.

4) Since you can put several 64 port cards into a single PC (easily 3
   or 4) you can manage a LOT of devices from a single console server
   this way...

It's really a very good solution and can be used not only for workstations
but also for routers, hubs, NetApp servers, etc., etc.

The only downside of using serial consoles with Suns is that Suns have
the annoying habit of dropping into the ROM monitor when power to the
console server is lost (they interpret this as a "break" condition).
As best I can tell this is the case for any serial console hooked up
to a Sun, even a dumb terminal.

The workaround is to never shut down the power to the console server
(reboot is fine), and if you absolutely must, disconnect all the
serial cables first.  Older Suns also sometimes drop into the monitor
if you just disconnect the cable, but we've found that this can be
prevented by putting a resistor across the right pins.  Actually one
can prevent break conditions altogether by putting a resistor across a
certain set of pins, but then you can't drop into the boot monitor
anymore, so that's not desireable.  If anyone has an optimal solution
to this problem, I'd love to hear it...

- Jürgen