Kubernetes - Secrets vs ConfigMaps

Secret ConfigMap
What is? Secrets are k8s object to manage small amount of sensitive data like password, keys and tokens with less than 1mb size. Secrets encoded and stored inside k8s master etcd data store. Since Secrets will be created outside of pods and containers, these can be used any number of times ConfigMaps used to seperate container images and its custom configurations so that images are portable and can be run in any environment providing appropriate configuration. `ConfigMap` stores data in key, value format. If any configuration values are sensitive the use `Secret` instead `ConfigMap`. Its must to create `ConfigMap` before hand if we need to refer in pod spec
Create using `kubectl` #syntax
kubectl create secret < data from-file|from-literal>
echo -n ‘admin’ > ./username.txt
echo -n ‘1f2d1e2e67df’ > ./password.txt
kubectl create secret generic db-user-pass –from-file=./username.txt –from-file=./password.txt
kubectl create secret generic dev-db-secret –from-literal=username=user –from-literal=password=’S!B\*d$zDsb=’ 		#syntax
kubectl create configmap < data from-file|from-literal>
path/to/config/file/application.yaml
path/to/config/file/application-prod.properties
kubectl create configmap app-config –from-file=path/to/config/file/
#list the content of properties and yml file configuration
kubectl get configmaps app-config -o wide
kubectl create configmap custom-config –from-literal port=8080 –from-literal https=false
Create using yaml manifesto files 
                    
    #sample yaml manifesto secret.yaml file 
    apiVersion: v1
    kind: Secret
    metadata:
        name: mysecret
    type: Opaque
    data:
        username: appuser
        password: MWYyZDFlMmU2N2Rm
 
 
create using kubectl apply
    kubectl apply -f ./secret.yaml
                
            
                
    #sample yaml manifesto configmap.yaml file 
    apiVersion: v1
    kind: ConfigMap
    metadata:
        name: myconfig
    type: Opaque
    data:
        port: 8080
        https: false
 
 
 
create using kubectl apply
    kubectl apply -f ./configmap.yaml
Deploy within Pods, Using Volumes 
                
                #sample pod manifesto yaml file
                apiVersion: v1
                kind: Pod
                metadata:
                    name: nginx
                spec:
                    containers:
                    - name: nginx
                      image: nginx
                      volumeMounts:
                      - name: secret-volume
                        mountPath: /etc/secret
                        readOnly: true
                    volumes:
                    - name: secret-volume
                      secret:
                        secretName: mysecret    
                     
                
                
    #sample pod manifesto yaml file
    apiVersion: v1
    kind: Pod
    metadata:
        name: nginx
    spec:
        containers:
        - name: nginx
          image: nginx
          volumeMounts:
          - mountPath: /target/
            name: custom-config
        volumes:
        - name: custom-config
          configMap:
            name: app-config
            items:
            - key: application.yaml  
              path: application.yaml
            - key: application-prod.properties
              path: application-prod.properties
Deploy within Pods, Using environment variables 

    #sample pod manifesto yaml file
    apiVersion: v1
    kind: Pod
    metadata:
        name: nginx
    spec:
        containers:
        - name: nginx
          image: nginx
          env:
          - name: SECRET_USERNAME
            valueFrom:
                secretKeyRef:
                    name: mysecret
                    key: username
          - name: SECRET_PASSWORD
            valueFrom:
                secretKeyRef:
                    name: mysecret
                    key: password


Instead of volume mapping use environment variables
and use secret(ie. mysecret) to assign values. 
Verify the environment variables.
 
    kubectl exec nginx env | grep SECRET
        => SECRET_PASSWORD=MWYyZDFlMmU2N2Rm
        => SECRET_USERNAME=appuser
                    

    #sample pod manifesto yaml file
    apiVersion: v1
    kind: Pod
    metadata:
        name: nginx
    spec:
        containers:
        - name: nginx
          image: nginx
          env:
          - name: CONFIG_PORT
            valueFrom:
                configMapKeyRef:
                    name: myconfig
                    key: port


Instead of volume mapping use environment variables
and use configmap(ie. myconfig) to assign values.
Verify the environment variables.
 
    kubectl exec nginx env | grep CONFIG
        => CONFIG_PORT=8080