hi,

> I run a headless sparc64 with serial console (ttya). Occassionally,
> however, I want to temporarily use ttyb to enable my box as a serial
> console for other headless machines -- but connecting/disconnecting
> anything on ttyb invariably causes enough of a power flux on the port 
> to
> emulate a serial BREAK, at which point the kernel drops into ddb.
> If I am on location I suppose I can just say continue in ddb and be 
> happy,
> but it is still inconvenient, at best.
>
> I couldn't find much on google apart from an old kernel patch to
> completely disable ddb on serial BREAK, and ddb(4) had no enlightenment
> for me either.
>
> I presume it is not possible to tell the kernel to ignore BREAKs on 
> serial
> ports that don't have a console device attached to them? Could I easily
> patch it to work this way myself?
>
> -- 
> /ali
> :wq

IIRC ttya comes up immediately when the system starts while ttyb gives 
you a login shell when entering runlevel 3. so i'd consider a try going 
the ttyb way and see whether it 'ignores' unplugging the cable.

unplugging the serial cable from ttya gives the machine an NMI (that's 
what i remember from the Solaris side of life). there was a patch or 
package for Solaris 2.5.1 IIRC to workaround this behaviour... but this 
is NetBSD.

maybe ttyb is worth a try (i can't test it myself right now because i'm 
not at home where my sparcies are :(

regards,

timo

:x!