Big problem!

Gavin McCullagh gmccullagh at
Wed Jan 31 09:28:20 GMT 2007


I might ask a few questions to see can we tease this out better.

On Tue, 30 Jan 2007, don Paolo Benvenuto wrote:

> Since two weeks I have a big problem with my edubuntu ltsp installation.
> All were working without problem, but the hd failed, and I have to
> reinstall all the stuff.

Just to be clear what has changed:

 - What version of Edubuntu were you running before and what version are
   you running now after reinstall?  Was your previous version upgraded or
   did you install that version directly.
 - This is still the same physical server, right?
 - You replaced a hard disk.  Was this with an identical new hard disk or
   did something change?  Are you still using the same disk controller?  Is
   it IDE, SATA or SCSI?  Are you using RAID of any sort?

> Normally I mantain the server all the time swithced on. When I boot the
> clients in the morning, almost all boot up, one or two don't boot and
> they stop with an arror in the nfs mounting, so that the busybox shell
> appears.
> But if I switch the clients off and boot them again, almost all don't
> boot, and stop with the nfs mounting problem.

Did all thin clients always boot before you reinstalled or did you see this
problem sometimes and now it's got much worse?

If you boot each client one at a time, do you get less failures than if you
boot many together?  Can you get back to most clients working by rebooting
the server or restarting the nfs server?
	sudo /etc/init.d/nfs-kernel-server restart

> I'm quite sure it's not a software problem, and I was wondering if it
> could be a hardware one. So that I ask you: how do I realize what is
> failing? What should I check?

On the server, you could 

1. check the output of the command dmesg for errors.
2. check the logfiles, particularly /var/log/syslog and /var/log/messages
   for errors
3. look at the output of "/sbin/ifconfig" and look at the error count.  It
   should generally be zero.
3. look at the output of 
	sudo /usr/sbin/ethtool eth0
   to see what speed the NIC is negociated at, etc.

> My net wiring: the server's nic is connected to two 24-ports switches
> (D-Link), and every switch is connected to 20 clients, 40 clients for
> all.
> When the problem appears, it affects the clients of both switches.

Is everything 100Mbit/sec or have you some Gigabit (or 10Mbit/s) equipment?
I presume one switch plugs into the other which does create a bottleneck
for the switch further away from the server.  This would not have been new
after a reinstall though.

> If a client doesn't boot, preferebly isn't one of the clients nearest to
> server.

You mean the clients nearer the server boot correctly more reliably than
those further away?  Do those machines have something in common, eg type of
machine, what switch they're on? 


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