[root@k8smaster4 mysql]# cat mysql.yaml 
apiVersion: v1
kind: ConfigMap
metadata:
  name: mysql-configmap
  labels:
    environment: test
    app: mysql
data:
  up: "1"
  lower: "3"

[root@k8smaster4 mysql]# cat mysql-envFrom.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: mysql-envfrom
  labels:
    environment: test-envfrom
    app: mysql-envfrom
spec:
  containers:
  - name: mysql-envfrom
    image: docker.io/library/busybox
    imagePullPolicy: IfNotPresent
    command: ["/bin/sh","-c","sleep 3600"]
    env:
    - name: login_in
      valueFrom:
        configMapKeyRef:
          name: mysql-configmap
          key: up
    - name: login_off
      valueFrom:
        configMapKeyRef:
          name: mysql-configmap
          key: lower
  restartPolicy: Never

[root@k8smaster4 mysql]# kubectl get pods -l app=mysql-envfrom
NAME            READY   STATUS    RESTARTS   AGE
mysql-envfrom   1/1     Running   0          103s

[root@k8smaster4 mysql]# kubectl exec -it mysql-envfrom -c mysql-envfrom -- /bin/sh
/ # printenv
login_in=1
KUBERNETES_SERVICE_PORT=443
KUBERNETES_PORT=tcp://10.96.0.1:443
HOSTNAME=mysql-envfrom
SHLVL=1
HOME=/root
NGINX_TEST_SERVICE_HOST=10.105.242.121
NGINX_TEST_PORT=tcp://10.105.242.121:80
NGINX_TEST_SERVICE_PORT=80
TERM=xterm
KUBERNETES_PORT_443_TCP_ADDR=10.96.0.1
NGINX_TEST_SERVICE_PORT_WEB=80
NGINX_TEST_PORT_80_TCP_ADDR=10.105.242.121
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
KUBERNETES_PORT_443_TCP_PORT=443
login_off=3
KUBERNETES_PORT_443_TCP_PROTO=tcp