Kubernetes 101 : Pause containers

Pause container:

The pause container is a  container that exits in each pod, it's like a template or a parent containers from which all the new containers in the pod inherit the namespaces.

The pause container starts, then goes to "sleep".

It is a "template" container that reserves the namespaces which are shared among all the containers inside the pod.

Even if the last container in a network namespace crashes, the namespace would still be there, because we would still have the pause container "holding" the namespace.

Container A and B crash, The network namespace is still there, held by the pause container.

Since the Pause container is still there, the Pod also keeps it's IP address.

Communication between the containers in a pod:

The pause container makes it possible for the containers to communicate between each other through the localhost (loopback address).

The IP address is "exposed" at the pod level, containers within a pod share an IP address but run on different ports related to the different applications running inside them.


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