This labels allow to use some environment variables from another service
and use the configMap / secret instead of the original value. This is
useful to avoid duplication of values for several variables.
Ingress has some default values, like path and classname. We need to
ensure that values are taken or nil, and to apply them if they are not
set explicitally. Port is a sepcial case.
This volumes are "emptyDir" and can have init command. For example, in a
"same-pod", it allow the user to copy data from image to a directory
that is mounted on others pods.
metal3d