Re: kernel problems


Subject: Re: kernel problems
From: Fielder George Dowding (fgdowding@iceworm-enterprises.net)
Date: Mon Jul 15 2002 - 08:36:31 AKDT


Greetings schu,

According to D.J. Bernstein http://cr.yp.to the problem is sendmail.
I can't find his discussion of this very problem with sendmail, but
it was somewhere on his site. His solution is use qmail as a dropin
replacement for sendmail.

I am not making a recommendation. I have not yet set up any e-mail
servers, but when I do, I will not use sendmail.

Cheerio! fgd

On Sun, 14 Jul 2002 22:45:38 -0800
Matthew Schumacher <schu@schu.net> wrote:

>
> Hello all,
>
> Last week a mail server I manage suddenly failed so I tried to get
> a shell to the server and found that I can login but bash would
> hang. I thought this to be interesting to I passed a 'ps -ef'
> though ssh to the machine to see if that would work. To my
> surprise it did. I got a list back of 248 processes. After
> further investigation it seems that my box hit a process limit and
> simply would not start a bash shell (but it did start a ps which
> is odd). Anyway I started passing kill commands though ssh to try
> and shut it down but kill wouldn't work, kill -9 wouldn't work,
> killall wouldn't work, shutdown wouldn't work, nothing I did would
> kill a process. After fighting with it for about an hour I drove
> to the co-lo room and hit the switch.
>
> Does anyone know what might cause this? Why would the kernel
> simply refuse to kill anything. Btw, the box normally has 110-130
> processes running so something had to happen to cause it to hit
> 248. The extra processes looked to be stale sendmail/qpopper/imap
> processes.
>
> The machine is running redhat 7.3 with the redhat 2.4.18-4 kernel.
> I tried using a generic kernel I compiled but my scsi performance
> dropped in half. After some conversation with Alan Cox he says
> that redhat patches some hi-mem/scsi code to their kernels which
> fixes some performance problems with the generic kernel. I also
> had a lot of trouble using quotas under heavy load with the
> generic kernel so alas I am running a redhat kernel.
>
> Anyway, I really can't deal with software failure on this machine.
> Hopefully someone will have a suggestion on how to trouble shoot
> this. If not maybe I'll start testing FreeBSD....
>
> Later,
>
> schu
>
>
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