generic: 通用型，通常用于存储密码数据
tls: 此类型仅用于存储私钥和证书
docker-register: 若要保存docker仓库认证信息，就必须使用此种类型来创建

Service Account: 用于被service Account引用
0paque： base64 编码格式的seret，用来存储密码、秘钥。可以通过base64 --decode解码
kubernetes.io/dockerconfig.json: 存储私有docker registry认真信息

kubectl create secret generic mysql-password --from-literal=password=xianchaopod**lucky66

[root@k8smaster4 sc]# kubectl describe secret mysql-password
Name:         mysql-password
Namespace:    default
Labels:       <none>
Annotations:  <none>

Type:  Opaque

Data
====
password:  20 bytes

[root@k8smaster4 sc]# cat pod-secret.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: pod-secret
  labels:
    environment: secret-test
    app: myapp
spec:
  containers:
  - name: secret-test
    image: docker.io/janakiramm/myapp:v1
    imagePullPolicy: IfNotPresent
    ports:
    - name: http
      containerPort: 80
    env:
    - name: MYSQL_ROOT_PASSWORD
      valueFrom:
        secretKeyRef:
          name: mysql-password
          key: password