CentOS server not responding

You sure there's nothing in the logs?

You could configure Apache's MPM worker to restrict the number of processes it starts/manages.

There is also a little-known DDoS attack which keeps connections alive (HTTP's Keep-Alive mechanism) instead of closing them when it's finished, and this can cause hundreds of additional processes to start as Apache believes it's handling requests from these DDoS processes and generates new ones for new processes.

When you restart Apache, it kills off these rogue processes and hence the connections, so it depends how long it takes for the attacker to realise it's gotten disconnected and try again.

You could also enable the server-status and server-info handlers and watch them when it starts getting busy to identify what the server's doing.

http://httpd.apache.org/docs/2.2/mod/mod_status.html

http://httpd.apache.org/docs/2.2/mod/mod_info.html

I am not a linux guru, more of a noob actually, but in order to execute the shutdown script you must create a lock file in /var/lock/subsys/ folder in your startup script. I found the answer here: CentOS Forum

Script example:

#!/bin/sh
# chkconfig: 345 98 11
# description: my auto start-stop script.

echo "my service is doing something :)" >> /root/tempfile
case "$1" in
 start)
  echo "my service started" >> /root/tempfile
  touch /var/lock/subsys/myservice
  echo "OK"
  ;;
 stop)
  echo "my service stoped" >> /root/tempfile
  rm -f /var/lock/subsys/myservice
  echo "OK"
  ;;
esac