Is it possible in Kubernetes to mount a file from a ConfigMap into an directory that already has other files? E.g.
Base image filesystem:
/app/
main/
main.py
test.py
ConfigMap contains one file, mounted.py, which should be mounted in /app/main/ alongside main.py and test.py.
Desired filesystem after deployment:
/app/
main/
main.py
test.py
mounted.py
What I have seen so far is that the ConfigMap is mounted to a new directory, so the closest I have come is like this:
/app/
main/
main.py
test.py
mounted/
mounted.py
If I mount the ConfigMap to /app/main, then it clobbers the existing files from the base image. E.g.
/app/
main/
mounted.py
Is there a good way to inject a single file like that? (Actually multiple files in my real use case.) I would prefer not to have separate directories for everything that will be injected by the ConfigMaps, since it deviates from the standard program architecture.
Use subPath:
volumeMounts:
- name: config
mountPath: /app/main/mounted.py
subPath: mounted.py
The mountPath shows where it should be mounted, and subPath points to an entry inside the volume.
Please be aware of the limitation: when using subPath the configMap updates won't be reflected in your file. See the official documentation for details.