I'm having an issue with what I believe is Apache. Things will be running nicely, then all of a sudden things will just 'blow up'. Apache seems to fork a bunch of new processes, and it starts ripping into the memory. I've had it essentially eat through all the free memory and swap, and the system will then freeze up as there's no more memory. This is a CentOS server running CPanel, the configuration had been up and running for a long time without problems then this suddenly started happening. Has anyone come across anything similar or can anyone suggest the best place to start looking.
I can provide more details if needed, just let me know what you want.
Can you use top command and monitor the server and see which process is consuming maximum cpu or memory? Once this is confirmed you can run a starce -p <pid> where pid is the process id which is consuming excessive memory this will show you what makes apache go unresponsive.
First check the apache status from WHM and find out if there is any specific website causing huge traffic on the server. IF thats not the case it can be a DDOS attack as well so you can find more by using the netstat command. Plenty of resources are available to avoid ddos attacks.
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If you can have a SSH session open at the same time as viewing the extended server-status (which I believe Srv24x7 is talking about), you should be able to see which processes are being hogs, take note of the PID and look up what is being accessed in the extended server-status. Do this enough you should be able to get a handle on and track down what ever is causing this. I can not jump to the conclusion that it is a DDOS without a lot more information. That would sort of be like how doctors toss about eczema for any skin condition that they can not directly identify or explain.