Execute a Script in a Container on Startup in OpenShift

1. Confirm the process ID (PID) of the target process in a running container. It is common, though not required, that Liberty is PID 1.
2. Edit the pod or deployment YAML. For example:

   oc edit deployment deployment1

3. Add a lifecycle.postStart.exec.command element to the target container that executes a diagnostic script. For example, the following sleeps 5 seconds and then gathers 5 javacores 10 seconds apart (change PID as required):

   spec:
     containers:
     - name: ...
       lifecycle:
         postStart:
           exec:
             command: ["/bin/sh", "-c", "echo 'sleep 5; PID=1; i=0; while [ $i -le 5 ]; do kill -3 $PID; sleep 10; i=$(( i + 1 )); done' > /tmp/diag.sh; chmod +x /tmp/diag.sh; /tmp/diag.sh &"]

4. Save the YAML and the pod/deployment will restart

Notes:

1. The script is run in the background because Kubernetes won't set the container to RUNNING until the postStart script "completes".

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