Caveat to mounting individual config map entries as files

Mounting individual config map entries as files doesn’t hide files in that directory as contrast to mounting the entire config map as a directory. However, there is one caveat to this: the mounted files are not updated when the config map values are changed. The pods in question needs to be restarted for the mounted files to be updated.

Below is an example of a custom nginx config file mounted as an individual file at /etc/nginx/conf.d/gzip.conf in the container.

apiVersion: v1
kind: ConfigMap
metadata:
  name: myconfig
data:
  mynginx.conf: |
    # my custom nginx configuration

    server {
        listen 80 default_server;
        listen [::]:80 default_server;

        root /usr/share/nginx/html;

        # Add index.php to the list if you are using PHP
        index index.html index.htm index.nginx-debian.html;

        server_name _;

        gzip on;

        location / {
            # First attempt to serve request as file, then
            # as directory, then fall back to displaying a 404.
            try_files $uri $uri/ =404;
        }
    }    

apiVersion: apps/v1
kind: Deployment
spec:
  template:
    spec:
      containers:
      - name: mount
        image: nginx:latest
        ports:
        - containerPort: 80
          name: http
        volumeMounts:
        - name: config
          ## mounting entire directory
          # mountPath: /etc/nginx/conf.d
          ##

          ## mounting a single file
          mountPath: /etc/nginx/conf.d/gzip.conf
          subPath: mynginx.conf
          ##
      volumes:
        - name: config
          configMap:
            name: myconfig
      restartPolicy: Always
---

kubectl exec -it mount-5d4ffd47b8-rrjls -- /bin/bash

root@mount-5d4ffd47b8-rrjls:/# ls -l /etc/nginx/conf.d/
total 8
-rw-r--r-- 1 root root 1093 Aug 27 06:51 default.conf
-rw-r--r-- 1 root root  460 Aug 27 06:51 gzip.conf

Had the config map be mounted as a directory, the default.conf file would be invisible.

Now go ahead and make changes to the mynginx.conf value, you’ll notice the gzip.conf file is not updated.

kubectl edit configmaps myconfig
#K8s