hooks: start with pre-start and post-stop hooks.

Signed-off-by: Mrunal Patel <[email protected]>

runtime.md

@@ -15,3 +15,20 @@ Runs a process in a container. Can be invoked several times.
 Not sure we need that from oc cli. Process is killed from the outside.
 
 This event needs to be captured by oc to run onstop event handlers.
+
+## Hooks
+Hooks allows one to run code before/after various lifecycle events of the container. The state of the container is passed to the hooks over a well-known fd, so the hooks could get the information they need to do their work.
+
+### Pre-start
+The pre-start hook is called before the container process is started. It provides an opportunity to customize the container. In Linux, for e.g., the network namespace could be configured in this hook.
+
+### Post-stop
+The post-stop hook is called after the container process is stopped. Cleanup or debugging could be performed in such a hook.
+
+```
+    "hooks" : {
+        "pre-start": ["/path/to/pre-start-hook", "arg1", "arg2"],
+        "post-stop": ["/path/to/post-stop-hook", "arg1"]
+    }
+```
+