Initialization containers are containers that can be defined on your Pod, and will be invoked in the specific sequence that they are defined prior to your main container (or containers) being started. Initialization containers became a normal part of Pod specification in Kubernetes version 1.6.
These containers can use the same container image and simply have alternate commands, but they can also use entirely different images, leveraging the Kubernetes Pod guarantees of shared network and filesystem mounts to do initialization and setup work prior to the main container operating. These containers also use namespaces, so they can be given specific access that the main container doesn't have; consequently, they can be given access to Kubernetes Secrets that the main container cannot access.
Initialization containers are expected to have code that runs to completion and exits with a success response. As mentioned previously, these containers are also invoked in sequence...
