[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]# kubectl get configmap mysql-configmap
NAME              DATA   AGE
mysql-configmap   2      20s
[root@k8smaster4 mysql]# kubectl describe cm mysql-configmap
Name:         mysql-configmap
Namespace:    default
Labels:       app=mysql
              environment=test
Annotations:  <none>

Data
====
lower:
----
3
up:
----
1

BinaryData
====

Events:  <none>

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

[root@k8smaster4 mysql]# kubectl get pods
NAME                               READY   STATUS      RESTARTS         AGE
busybox                            0/1     Completed   0                16d
mysqlcm-test                       1/1     Running     0                5s
nfs-provisioner-6f77f76894-v96h6   1/1     Running     17 (3d13h ago)   37d
test-storageclass                  1/1     Running     5 (3d13h ago)    37d
web-0                              1/1     Running     3 (3d13h ago)    16d
web-1                              1/1     Running     3 (3d13h ago)    16d

[root@k8smaster4 mysql]# kubectl exec -it mysqlcm-test -c mysql-config -- /bin/sh
/ # printenv
KUBERNETES_PORT=tcp://10.96.0.1:443
KUBERNETES_SERVICE_PORT=443
off_bin=3
HOSTNAME=mysqlcm-test
SHLVL=1
HOME=/root
NGINX_TEST_SERVICE_HOST=10.105.242.121
NGINX_TEST_SERVICE_PORT=80
NGINX_TEST_PORT=tcp://10.105.242.121:80
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
login_bin=1
KUBERNETES_PORT_443_TCP_PORT=443
NGINX_TEST_PORT_80_TCP_PORT=80
KUBERNETES_PORT_443_TCP_PROTO=tcp
NGINX_TEST_PORT_80_TCP_PROTO=tcp
KUBERNETES_SERVICE_PORT_HTTPS=443
KUBERNETES_PORT_443_TCP=tcp://10.96.0.1:443
NGINX_TEST_PORT_80_TCP=tcp://10.105.242.121:80
KUBERNETES_SERVICE_HOST=10.96.0.1
PWD=/