Serial Console

John Brookes johnb at
Sat Jul 13 14:42:46 PDT 2002

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

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).
3) You don't mention which nodes you've got. (Especially?) If you've got
Alphas, you are may also have to turn off kudzu, or at least change the
config file (/etc/sysconfig/kudzu) so that it does a safe search (which
doesn't look at the node's serial ports.....searching them can scramble the
port's initialisation)

Use the fastest possible connection speed (linux install will annoy you
greatly otherwise), but make sure a speed is supported for whichever
nodetype you've got (most nodes can handle 115200 nowadays, but don't take
it for granted.)

Ah, actually just noticed that you're taking about going to 7.3 (i.e. nodes
are not Alphas), so you can keep kudzu on (AFAIK).


John Brookes
QSW (Quadrics) Ltd.
T: +44 (0)117 9155500
F: +44 (0)117 9075395
E: johnb at

> -----Original Message-----
> From: Timothy W. Moore [mailto:moor007 at]
> Sent: 13 July 2002 18:54
> To: beowulf at
> Subject: Serial Console
> This should be in the Redhat docs...and if it is, I have been 
> unable to 
> find it.
> I built an 8-CPU cluster, and because I am not a linux guru, took the 
> lazy route and used a KVM switch.  I upgraded my networking with GigE 
> that now occupies the riser slot...former resting place of my video 
> card.  I now want to upgrade to Redhat 7.3 without the benefit of a 
> video card and have no idea where to begin.  The first question is 
> I need a special card?  switch? The second question is 
> software...what files do I change to redirect the ouput to 
> com2(?)?  If 
> there is an Idiot's guide (step by step) on the net, the URL would be 
> greatly appreciated.  Remember...I know absolutely nothing about this 
> topic.
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