Serial Console

Iain Rae iainr at
Sun Jul 14 07:23:39 PDT 2002

John Brookes wrote:

>Hi Tim(othy?),
>You're going to want a single piece of specialist hardware; a terminal
>concentrator (aka terminal server). There are plenty currently on the market
>and I'm not going to mention any of them, because they're all OK and
>probably the best guide is the price that you can source them for locally.
>You really want (a cheap) one of these if you don't sit next to your

It's also possible to do this slightly cheaper with serial port cards 
and software like conserver (

You'll need to check that serial console support for the kernel is built 
in (I think this is the case with redhat) and have something like


in your lilo.conf or

  serial --unit=0 --speed=9600
  terminal --timeout=1 serial   
 kernel......console=ttyS0, 9600

in your grub menu.lst file

you may want to take a  look at the magic SySRq stuff and have than 
enabled in the kernel as well


which allows you to do things like reboots on machines that are 
completely locked up.

>Terminal servers are v. cool. No special software is usually required (other
>than that which you get with the terminal server manufacturer), but I'd
>advise you to make sure that they don't require stupidly hassly wiring
>(unless you've got lots of PhD students :). Oh, stick the terminal server on
>a network that doesn't require the head node of the cluster to be up to
>access the thing, otherwise you'll become irritated sooner or later.

>1) Some terminal servers mess things up with some BIOSes - check the web
>before you buy! Get a version of your BIOS that doesn't require you to press
>'F2' or the like (your family - should you have one - will thank me for this
>nugget ;)
>If you're Linuxing:
>2) You'll need to add a line like "0:2345:respawn:/sbin/agetty 115200 vt100"
>to /etc/inittab. The '0' is just a label, '2345' specifies the runlevel that
>this console should be accessible in, 'respawn' means don't kill the process
>just because I log out and the last bit specifies the getty, connection
>speed and terminal emulation to use. Often a line like,
>"0:2345:respawn:/sbin/mingetty" will do the trick (slap self on wrist - 'man
>mingetty', or summat, says not to use it for serial consoles).

we use
T1:2345:respawn:/sbin/agetty -L 9600 ttyS0 vt100

Iain Rae			Tel:01316505202
Computing Officer		JCMB:2148
Division of Informatics
The University of Edinburgh

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