I have a machine running Ubuntu Server that experienced severe problems today, for no apparent reason. Two of the services that it's running are apache2 and ssh, and during the period the server was slow I wasn't able to access either.
I've been checking the logs in /var/logs/
. This hasn't shed any light into the matter, but then again, I'm not sure what I'm looking for...
How can I diagnose the problem, so that I can take measures to prevent it from happening again in the future?
The full story/details:
- Today during a class I've given out an exercise (sort of an exam) to around 35 computer-science students. They were supposed to access two instances of Trac that I had previously installed in my server. Each student had their own login credentials.
- The server is actually a VMWare virtual machine with Ubuntu 11.10, and lives in the same network from which the students were accessing it.
- When the exam started, the students entered an address that they were given into their web-browsers. Three of them actually managed to see trac's first webpage, but after that, the server became totally unresponsive (the browsers just kept waiting until they timed out)
- I've also tried accessing a server console, via SSH and via the VMWare VSphere Client, but on both cases the console was also totally unresponsive.
- I wasn't sure what else to try, so I've reset the virtual machine. It booted, but nothing changed after that: all the services I've mentioned above remained unresponsive.
- I've booted it again --- nothing new.
- At this point I sent everyone home, as we no longer had enough time for the exam. When about half of them had the laptop shutdown, the server started responding again. I don't think this was a coincidence, but still can't explain what the server problems were exactly and how to prevent them.
Update
The hardware assigned to this particular VM is:
- 1 CPU
- 512MB Memory
- 60GB Hard Disk space (with currently 80% free)