What do hostPID and hostIPC options mean in a kubernetes pod?

Question

In kubernetes pod yaml specification file, you can set a pod to use the host machine's network using hostNetwork:true.

I can't find anywhere a good (suitable for a beginner) explanation of what the hostPID:true and hostIPC:true options mean. Please could someone explain this, assuming little knowledge in linux networking and such. Thanks.

spec:
  template:
    metadata:
      labels:
        name: podName
    spec:
      hostPID: true
      hostIPC: true
      hostNetwork: true
      containers:

Source: github link here

Answer 1

they're roughly described within the Pod Security Policies

hostPID - Use the host’s pid namespace. Optional: Default to false.

hostIPC - Use the host’s ipc namespace. Optional: Default to false.

Those are related to the SecurityContext of the Pod. You'll find some more information in the Pod Security design document.