dialling into a pe2600 (ot?)

Andy Stubbs andrew.stubbs at activehotels.com
Wed Mar 12 11:42:01 CST 2003


I'm dialling in to one of our PE 2600 machines running Red Hat 7.3
(2.4.18-10smp) and using mgetty. Although I can enter a username,
sometimes the password prompt doesn't "work" - i.e., password is echo-ed
to screen and login times out. When I can log-in, bash hangs after running
non-builtin commands.

I've determined that when the password prompt doesn't work, I can type ^C
and then I can type the password and the login works correctly.  I've also
determined that I can type ^C and ^\ to make the shell respond again.
Also, from within emacs (and at some point as it starts up I have to do ^G
to make it respond), I can run a shell with no problems.

It's less than a coincidence that these correspond to the terminal special
characters intr and quit - which appear to flush the output buffer. Why
should this work? Well, after much scratching-of-head, stracing, puzzled
examination of linux/soundcard.h, examining the bash source code, and
googling, I finally worked out that bash is hanging on an ioctl - TCSETSW
to be precise - which is waiting for the output buffer to be flushed
before altering the termios struct associated with the dialin terminal
(ttyS1 in this case).

Having determined all this, I'm trying to work out how to prevent this
from happening. Does anybody else here have any experience of this issue 
and how to fix it? Funny how the login occasionally works correctly - 
makes me think this is something of a modem status/stty ttyS1/mgetty 
config thing. I say funny, but it's anything but funny when you're trying 
to reconfigure the switch which has brought the network down along with 
your e-commerce website and you have directors breathing down your neck 
and frothing at the mouth.

Apologies if this is ever-so-slightly off-topic - the PowerEdge link is 
tenuous, but I'm desperate!

How do other people manage this kind of situation? Dialling in to DRAC 



Andy Stubbs, B.A., Ph.D.
Network Manager, Active Hotels Ltd.
+44 1223 578106

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