How do I attach a configmap to a deployment in Kubernetes? - kubernetes

Question

Based on the instructions found here (https://kubernetes.io/docs/tasks/access-application-cluster/connecting-frontend-backend/) I am trying to create an nginx deployment and configure it using a config-map. I can successfully access nginx using curl (yea!) but the configmap does not appear to be "sticking." The only thing it is supposed to do right now is forward the traffic along. I have seen the thread here (How do I load a configMap in to an environment variable?). although I am using the same format, their answer was not relevant.
Can anyone tell me how to properly configure the configmaps? the yaml is
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx
namespace: sandbox
spec:
selector:
matchLabels:
run: nginx
app: dsp
tier: frontend
replicas: 2
template:
metadata:
labels:
run: nginx
app: dsp
tier: frontend
spec:
containers:
- name: nginx
image: nginx
env:
# Define the environment variable
- name: nginx-conf
valueFrom:
configMapKeyRef:
# The ConfigMap containing the value you want to assign to SPECIAL_LEVEL_KEY
name: nginx-conf
# Specify the key associated with the value
key: nginx.conf
resources:
limits:
memory: "128Mi"
cpu: "500m"
ports:
containerPort: 80
the nginx-conf is
# The identifier Backend is internal to nginx, and used to name this specific upstream
upstream Backend {
# hello is the internal DNS name used by the backend Service inside Kubernetes
server dsp;
}
server {
listen 80;
location / {
# The following statement will proxy traffic to the upstream named Backend
proxy_pass http://Backend;
}
}
I turn it into a configmap using the following line
kubectl create configmap -n sandbox nginx-conf --from-file=apps/nginx.conf

Answer 1

You need to mount the configMap rather than use it as an environment variable, as the setting is not a key-value format.
Your Deployment yaml should be like below:
containers:
- name: nginx
image: nginx
volumeMounts:
- mountPath: /etc/nginx
name: nginx-conf
volumes:
- name: nginx-conf
configMap:
name: nginx-conf
items:
- key: nginx.conf
path: nginx.conf
You need to create (apply) the configMap beforehand. You can create it from file:
kubectl create configmap nginx-conf --from-file=nginx.conf
or you can directly describe configMap manifest:
apiVersion: v1
kind: ConfigMap
metadata:
name: nginx-conf
data:
nginx.conf: |
# The identifier Backend is internal to nginx, and used to name this specific upstream
upstream Backend {
# hello is the internal DNS name used by the backend Service inside Kubernetes
server dsp;
}
...
}