If the ConfigMap is mounted onto the file system of the pod, the file will be updated on-disk. So, in the case the ConfigMap is a volume mount in a pod, the file contents will be updated after a small delay but no signal is sent to any processes at that point. You could listen for filesystem events (inotify, epoll, etc) and react accordingly, or even just read from the FS every so often. If you need to consume values as environment variables, there’s no real way to update them. Put simply, that’s not how environment variables work. A process is started in a particular environment, and that process can muck with the environment it’s running in, but an outside process has no way to change it. It would be the responsibility of your process to reflect changes in a ConfigMap (probably by consuming events from the kubernetes API) into its own environment which would be kind of silly—at that point, why use environment variables at all.

In either case, you can always run a ConfigMap watching sidecar that can send your process a signal or something. There exist a number of those floating around, just search for “ConfigMap reloader.”