1. Создать Secret

kubectl create secret generic\
   secret-name \ 
   --from-literal=DB_host=mysql
   --from-literal=DB_user=root
   --from-literal=DB_password=P@ssw0rd

kubectl create secret generic\
   secret-name \ 
   --from-file=secret-file

echo -n 'mysql' | base64
bXlzcWw=
echo -n 'root' | base64
cm9vdA==
echo -n 'P@ssw0rd' | base64
UEBzc3cwcmQ=

secret.yaml

apiVersion: v1
kind: Secret
metadata:
  name: db-secret
data:
  DB_host: bXlzcWw=
  DB_user: cm9vdA==
  DB_password: UEBzc3cwcmQ=

2. Использовать Secret в конфигурации Пода:

yaml_with_secret.yaml

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    name: myapp-pod
spec:
 containers:
   - name: nginx
     image: nginx
     ports:
       - containerPort: 8080
     envFrom: 
       - secretRef:
           name: db-secret