Multiple serial consoles via null modem cable

[Jeremy Chadwick]

On Fri, Jan 15, 2010 at 08:34:17AM +0200, Marin Atanasov wrote:
> Thank you a lot for your feedback!
> 
> Now to the real question again, because I'm a little confused now - can I
> still get a usb-to-serial port converter having let's say 8 serial ports and
> then connect each machine to the usb-to-serial hub and manage them remotely
> from a single location (the host having the usb-to-serial hub)? That way I
> just specify a serial port number and I get to a specific machine?
>
> The model provided by Boris looks nice, and that was my initial idea, but
> I'm not sure if I could get it working under FreeBSD. Is conserver or
> conserver-com able to handle this? I know that cu uses COM1 only, but will
> conserver able to handle serial consoles on different ports, since the
> usb-to-serial port would appear as multiple serial ports.

I'm referencing the product Charles showed, but the topology would look
like this:

+------------------------+
|   USB to serial hub    |
|                       U1---- FreeBSD box running conserver
|                        |
|                        |
+-P1---P2---P3---P4---..-+
  |    |    |    |
  |    |    |    |
  |    |    |    `-- box #4
  |    |    `------- box #3
  |    `------------ box #2
  `----------------- box #1

"U1" is the uplink port, which has to connect to something -- in this
case the FreeBSD box where conserver would run.  The uplink port would
connect to a single USB port on the FreeBSD box.

The cabling between a port (Px) and a box would be serial (probably
DB9).

What you end up with on the FreeBSD box is a series of /dev entries
which are associated with all of the ports on the USB to serial hub,
using ucom(4).  For example:

/dev/ttyU0 = P1 = box #1
/dev/ttyU1 = P2 = box #2
...

You'd then tell conserver using its configuration file that "box name
foo is attached to /dev/ttyU0, box name bar is attached to /dev/ttyU1"
and so on.

Then to get access to the serial console of either foo or bar, you'd SSH
to the FreeBSD machine and type "console foo" or "console bar".  Voila.

Make sense?

-- 
| Jeremy Chadwick                                   jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |