k8s: configMap does not work in deployment

Question

We ran into an issue recently as to using environment variables inside container.

OS: windows 10 pro
k8s cluster: minikube
k8s version: 1.18.3

1. The way that doesn't work, though it's preferred way for us

Here is the deployment.yaml using 'envFrom':

apiVersion: apps/v1
kind: Deployment
metadata:
  name: db
  labels:
    app.kubernetes.io/name: db
spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: db
  template:
    metadata:
      labels:
        app.kubernetes.io/name: db
    spec:
      serviceAccountName: default
      securityContext:
        {}
      containers:
        - name: db
          image: "postgres:9.4"
          ports:
            - name: http
              containerPort: 5432
              protocol: TCP
          envFrom:
            - configMapRef:
                name: db-configmap

here is the db.properties:

POSTGRES_HOST_AUTH_METHOD=trust

step 1:

kubectl create configmap db-configmap ./db.properties

step 2:

kebuctl apply -f ./deployment.yaml

step 3:

kubectl get pod

Run the above command, get the following result:

db-8d7f7bcb9-7l788        0/1    CrashLoopBackOff   1      9s

That indicates the environment variables POSTGRES_HOST_AUTH_METHOD is not injected.

2. The way that works (we can't work with this approach)

Here is the deployment.yaml using 'env':

apiVersion: apps/v1
kind: Deployment
metadata:
  name: db
  labels:
    app.kubernetes.io/name: db
spec:
  replicas: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: db
  template:
    metadata:
      labels:
        app.kubernetes.io/name: db
    spec:
      serviceAccountName: default
      securityContext:
        {}
      containers:
        - name: db
          image: "postgres:9.4"
          ports:
            - name: http
              containerPort: 5432
              protocol: TCP
          env:
            - name: POSTGRES_HOST_AUTH_METHOD
              value: trust

step 1:

kubectl apply -f ./deployment.yaml

step 2:

kubectl get pod

Run the above command, get the following result:

db-fc58f998d-nxgnn                   1/1        Running        0            32s

the above indicates the environment is injected so that the db starts.

What did I do wrong in the first case?

Thank you in advance for the help.

Update:

Provide the configmap:

 kubectl describe configmap db-configmap

Name:         db-configmap
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
db.properties:
----
POSTGRES_HOST_AUTH_METHOD=trust

Answer 1

For creating config-maps for usecase-1. please use the below command

kubectl create configmap db-configmap --from-env-file db.properties