Re: system goes unresponsive

[steve%prd.co.uk@localhost (Steve Blinkhorn)]

Just to add that commenting out the crontab entries for daily
maintenance worked, in that the system did not go unresponsive last
night.   Not a long-term solution, obviously, so any further insights
(e.g., which bits of daily maintenance are likely to stress the
system?) might help save me some hours of toil.

--
Steve Blinkhorn <steve%prd.co.uk@localhost>

You wrote:
> 
> On Mon, Dec 17, 2012 at 4:59 AM, Steve Blinkhorn <steve%prd.co.uk@localhost> 
> wrote:
> > I have an i386 machine running NetBSD 4.0.1 that has run consistently
> > for several years.   There have been no recent changes to any part of
> > the configuration: it provides the backbone of my local network, name
> > service, file service etc. etc.
> >
> > A few days ago it started crashing, or so I thought, overnight.   It
> > was almost unresponsive, but not quite.   It would issue a login
> > prompt on a virtual terminal on its console, and echo the login but
> > not issue the password prompt.
> >
> > Since we had been the subject of a substantial DoS attack from China,
> > I assumed that was the problem, added a couple of extra rules on my
> > router firewall, but next morning same problem.
> >
> > So I thought, maybe there'se some form of attack that's causing the
> > system to run out of processes.   So last night I left top(1) running on
> > a virtual terminal.   This morning there was the same problem, but top
> > was still updating regularly and showing the system as essentially
> > 100% idle, with ample free memory and swap space, and only 75
> > processes (which is about baseline for this machine).
> >
> > I can't find any panic message in the logs, but from the absence of
> > the normal rhythm of log entries, it seems that the problem occurs
> > sometime around 0315, which strikes me as significant in terms of
> > daily housekeeping.
> >
> > Help in diagnosing this problem would be much appreciated.   I think
> > it's something very basic that I just haven't run into as a problem
> > before.
> 
> When it comes to older i386 hardware (I'm assuming older since you're
> using 4.x), I'm pessimistic.
> 
> 0315 is probably related to daily maintenance.
> 
> Machine hangs in NetBSD/i386 are overwhelmingly related to bad
> hardware in my experience.
> 
> Once it's getting stressed by daily maintenance, it's giong bad.
> 
> Check the smart status on the hard drives (assuming you're using IDE drives):
> 
> atactl wdX smart status
> 
> Look for bad errors.
> 
> Check the dmesg. Do a memory test. It's probably related to memory or
> a hard drive. Or maybe a marginal power supply.
> 
> Andy
>