📘 Notes: Mounting Volumes with Multiple Files¶

🔹 ConfigMap/Secret Volumes¶

• A ConfigMap or Secret can contain multiple key-value pairs, each key → a file.

• When mounted as a volume:

• By default → all keys become files inside the mounted directory.

• If you only want a specific key (file):

  • Use subPath → maps a single key to a file at the given mountPath.

👉 Example:

volumeMounts:
  - name: cm-vol
    mountPath: /etc/config         # Mount full ConfigMap directory
  - name: cm-vol
    mountPath: /etc/app/config.yaml
    subPath: app-config.yaml       # Mount only this key

🔹 General Rule (applies to all Volumes)¶

• Mount directory → when you need all contents (multiple files/keys).
• Mount with subPath → when you need just one file or want to avoid overwriting existing directory.

🔹 Why use subPath?¶

• Prevents overwriting default dirs (e.g., /etc/nginx/nginx.conf).
• Lets you map one ConfigMap/Secret key into a specific file location.
• Works with any volume type (ConfigMap, Secret, EmptyDir, HostPath, PVC).

✅ Shortcut Rule for Exam:

• No subPath → whole directory mounted.
• With subPath → single file/key mounted.