[svlug] "tailing" a /dev?

Ivan Passos lists at cyclades.com
Wed Jul 18 10:12:01 PDT 2001


On Tue, 17 Jul 2001, Robert L. Harris wrote:
>   I am setting up a console server,  basically a linux box (2.4.4 for now)
> running debian.  I'll take ttya from some sun boxes and use a null modem
> to connect to my linux box, then use "cu" from the uucp package to remotely
> access my consoles.

OK, so you're building a Console Access Server (CAS).

>   I need to basically "tail" the output, and idealy any input, on
> /dev/ttyS0 for instance.  That way if my console spits out some CPU error
> or ECC error before a reboot that doesn't log, I can catch it on my
> console serve.  Idealy it'll tail also so that if one of the admins logs
> in and changes something in the middle of the night and doesn't remember
> the exact steps, I can just cut, paste, print.

OK, first let me make the "input" and "output" terms clear. When I say
input, I'm talking about CAS input, i.e. data from the server to the CAS.
When I say output, it means data from the CAS to the server.

In this case, I don't think you need to log the output, because when you
type something on the console, it usually goes to the server as CAS
output, and then the server echoes it back to your display (as CAS input).
Thus, you only need to log the CAS input, at least for shell access. This
would not be true for GUI's, for instance.

Do you agree??

>   A while back I went digging for console servers and such and never found
> anything that worked.  Does anyone know how I can do this or a tool that'll
> tail the console for me without locking it so I can't access it?

I believe that conserver (http://www.conserver.com/) could help you do
what you need.

Also, if you're willing to try a commercial solution, Cyclades has a CAS
family called Cyclades-TS. It's a Linux-based 1U CAS with up to 32 ports
per 1U. The TS does support data buffering, but only for CAS input. If
that is not enough to address your problem, I believe it would be fairly
easy to change our software to support CAS output data buffering as well.

For more information about the TS, check out:


Hope this helps.


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