Let's perform the following steps to create a deployment with multiple containers and get a shell into running containers:

1. In this recipe, we will deploy PostgreSQL on OpenEBS persistent volumes to demonstrate shell access. Change the directory to the example files directory in src/chapter10/postgres, which is where all the YAML manifest for this recipe are stored. Create a ConfigMap with a database name and credentials similar to the following or review them and use the cm-postgres.yaml file:

$ cd postgres
$ cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: ConfigMap
metadata:
 name: postgres-config
 labels:
 app: postgres
data:
 POSTGRES_DB: postgresdb
 POSTGRES_USER: testuser
 POSTGRES_PASSWORD: testpassword123
EOF

2. Create the service for postgres:

$ cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Service
metadata:
  name: postgres
  labels:
    app: postgres
spec:
  type: NodePort
  ports:
   - port: 5432
  selector:
   app: postgres
EOF

3. Review the postgres.yaml file and apply it to create the PostgreSQL StatefulSet. We can use this to deploy the pods and to auto-create the PV/PVC:

$ kubectl apply -f postgres.yaml

4. Get the pods with the postgres label:

$ kubectl get pods -l app=postgres
NAME READY STATUS RESTARTS AGE
postgres-0 1/1 Running 0 7m5s
postgres-1 1/1 Running 0 6m58s

5. Get a shell into the postgres-0 container:

$ kubectl exec -it postgres-0 -- /bin/bash

The preceding command will get you shell access to the running container.