Good morning,

I'm very new to Docker and Kubernetes, and I do not really know where to start looking for help. I created a database container with Docker and I want manage it and scale with Kubernetes. I started installing minikube in my machine, and tried to create a Deployment first and then a StatefulSet for a database container. But I have a problem with the StatefulSet when creating a Pod with a database (mariadb or mysql). When I use a Deployment the Pods are loaded and work fine. However, the same Pods are not working when using them in a StatefulSet, returning errors asking for the MYSQL constants. This is the Deployment, and I use the command kubectl create -f deployment.yaml:

apiVersion: apps/v1beta1
kind: Deployment
metadata:
 name: mydb-deployment
spec:
 template:
  metadata:
   labels: 
    name: mydb-pod
  spec:
   containers:
    - name: mydb
      image: ignasiet/aravomysql
      ports:
       - containerPort: 3306

And when listing the deployments: kubectl get Deployments:

NAME               DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
mydb-deployment    1         1         1            1           2m

And the pods: kubectl get pods:

NAME                                READY   STATUS    RESTARTS   AGE
mydb-deployment-59c867c49d-4rslh    1/1     Running   0          50s

But since I want to create a persistent database, I try to create a statefulSet object with the same container, and a persistent volume. Thus, when creating the following StatefulSet with kubectl create -f statefulset.yaml:

apiVersion: apps/v1beta1
kind: StatefulSet
metadata:
 name: statefulset-mydb
spec:
 serviceName: mydb-pod
 template:
  metadata:
   labels: 
    name: mydb-pod
  spec:
   containers:
    - name: aravo-database
      image: ignasiet/aravomysql
      ports:
       - containerPort: 3306
      volumeMounts:
       - name: volume-mydb
         mountPath: /var/lib/mysql
   volumes:
    - name: volume-mydb
      persistentVolumeClaim: 
       claimName: config-mydb

With the service kubectl create -f service-db.yaml:

apiVersion: v1
kind: Service
metadata:
 name: mydb
spec:
 type: ClusterIP
 ports:
  - port: 3306
 selector:
  name: mydb-pod

And the permission file kubectl create -f permissions.yaml:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
 name: config-mydb
spec:
 accessModes: 
  - ReadWriteOnce
 resources:
  requests:
   storage: 3Gi

The pods do not work. They give an error:

NAME                    READY   STATUS             RESTARTS   AGE
statefulset-mydb-0      0/1     CrashLoopBackOff   1          37s

And when analyzing the logs kubectl logs statefulset-mydb-0:

`error: database is uninitialized and password option is not specified
You need to specify one of MYSQL_ROOT_PASSWORD, MYSQL_ALLOW_EMPTY_PASSWORD and MYSQL_RANDOM_ROOT_PASSWORD`

How it is possible that it does ask for these variables when the container has already an initialization script and works perfectly? And why it asks only when launching as statefulSet, and not when launching the Deployment?

Thanks in advance.