terminals randomly disconnecting

[Krsnendu dasa]

I have noticed a few other problems and narrowed down the problem (I think)
to either os problem or motherboard problem. (Don't think it is the switch
or the network card.) Read below for more details. Thanks for all tips.

On 07/01/2008, Gavin McCullagh <gmccullagh at gmail.com> wrote:
>
> Hi,
>
> On Mon, 07 Jan 2008, Krsnendu dasa wrote:
>
> > I am experiencing an unusual problem. Occasionally (every 15 mins or so)
> all
> > the terminals just disconnect. The terminals need restarting before they
> > work again.
>
> What you say all, you mean every thin client connected to the server?


Yes. Also windows computers that were connecting to the internet and using
dns through the edubuntu server also had disconnection problems. I changed
dhcpd.conf to get dns from another server and it seemed to fix the windows
laptop to internet problem.
I am having intermittent problems with samba also. One minute I can connect
to the shares on edubuntu then the next minute I can't then I can again. It
seems to take a long time for the server to register when new windows
computers in the workgroup have connnected. At one point I noticed that nmbd
wasn't running so I manually restarted it. This is after I had already
restarted samba using init.d and webmin.

Every 15 minutes is pretty nasty.  I guess at least it's easy enough to
> repeat if you're testing.


May not be exactly every 15 minutes, maybe closer to 30mins.

You say the clients need restarting and I gather the server doesn't.  Can
> you ping a thin client after this happens (ie without rebooting it)?  If
> you press <ctrl><alt><backspace> is that enough to restart the thin
> client?


I haven't tried this as I haven't been at school much. I will try it next
time I  am at school when it freezes.

> In what I think may be a related issue, some times when someone is logged
> in
> > their terminal freezes and the panel at the bottom of the screen which
> shows
> > which windows are open just has three tabs that all say untitled window.
>
> Have you had opportunity to watch top for a few minutes and see does some
> process go wild around this point?

I haven't noticed anything. I will look again and see if anything stands
out.

> Background: I am using 32 Edubuntu 7.04 on Intel Quad Core. 4 Gb RAM. I am
> > using directx ldm and smbldap.
>
> Would it be possible for you to try not using direct-x and go back to the
> default ssh method?


I can also try this, but my instinct (and the dns /samba problems) seem to
point to bigger connection problems than ldm.
I also get disconnected when I log in from home using nx.

> I am using a 100/1000 unmanaged switch which feeds 10/100 switches in each
> > class.
> >
> > Things I have already tried.
> > At first I thought it could be the 1000 switch, so I swapped it for
> another
> > one, but the problem remains.
>
> Was it another similar switch?  Could it be a problem between the
> switches?


The second time I used a different brand of switch and a 10/100 switch, so I
don't think the switch is to blame.

> Possible solutions:
> > Could upgrading to Gutsy help?
>
> It's hard to say without knowing what the cause of the problem is.


If may be my old windows conditioning, but I feel like a reinstall might
help... or not.

> Could it be the network card in the server?
>
> Sounds plausible.


I tried another network card and the same problems are there.


> Can someone help me debug this? Are there any log files I can check to
> trace
> > the origin of this problem?
>
> Yes:
>         /var/log/syslog
>         /var/log/messages
>         /var/log/kern.log
>         /var/log/daemon.log


I had a look there and couldn't find anything that stood out for me. A few
times I saw something that said "disconnected" or something like that.
Perhaps I will copy and paste a section around the time when a disconnect
happens and post it for any experts to analyse.

> Thanks for any help. This is really frustrating, because I had a very
> stable
> > system with K12LTSP 6, and now with Edubutnu 7.04 I have having quite a
> few
> > problems.
>
> How long have you had this problem?  You've been using 7.04 for a while,
> right?  Has it always happened?  Has anything changed to prompt this?


We installed some time in October. This problem has been only since
December. I can't think of anything that changed at that time. The last
thing I remember that changed is... A course management software web-based
application was installed and there were some changes to dns.
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