configMap 是一种快捷的修改容器内 变量的方式，由k-v组成，当修改configmap时 容器中的变量也会相应修改。
查看帮助文档

[root@node-1 ~]# kubectl explain pod.spec.containers.env.valueFrom.configMapKeyRef

[root@node-1 ~]# kubectl explain configmap

configmap 可以直接用命令创建也可以把value保存到文件中,此时文件名为key ,文件中的内容为value.
直接用命令：

[root@node-1 ~]# kubectl create configmap --help
 kubectl create configmap nginx-nc --from-literal=nginx_port=80 --from-literal=nginx_server=erick.com
 查看创建的cm
[root@node-1 ~]# kubectl get cm
NAME       DATA   AGE
nginx-nc   2      60s
[root@node-1 cm]# kubectl get cm nginx-nc -o yaml
apiVersion: v1
data:
  nginx_port: "80"
  nginx_server: erick.com
kind: ConfigMap
metadata:
  creationTimestamp: "2019-06-20T22:34:44Z"
  name: nginx-nc
  namespace: default
  resourceVersion: "432545"
  selfLink: /api/v1/namespaces/default/configmaps/nginx-nc
  uid: 9a180b6e-93ab-11e9-b0ae-080027edb92f
[root@node-1 cm]# 

把value以文件的方式存放

[root@node-1 cm]# cat www.conf 
server {
        server_name myapp.com;
        port 80;
        root /data/web/html;

}
[root@node-1 cm]# kubectl create configmap nginx-cm-from-file --from-file=./www.conf 
configmap/nginx-cm-from-file created
[root@node-1 cm]# kubectl get cm
NAME                 DATA   AGE
nginx-cm-from-file   1      7s
nginx-nc             2      9m7s
[root@node-1 cm]# kubectl get cm nginx-cm-from-file -o yaml
apiVersion: v1
data:
  www.conf: "server {\n\tserver_name myapp.com;\n\tport 80;\n\troot /data/web/html;\n\n}\n"
kind: ConfigMap
metadata:
  creationTimestamp: "2019-06-20T22:43:44Z"
  name: nginx-cm-from-file
  namespace: default
  resourceVersion: "433432"
  selfLink: /api/v1/namespaces/default/configmaps/nginx-cm-from-file
  uid: dbd2aa33-93ac-11e9-b0ae-080027edb92f
[root@node-1 cm]# 
也可以用describe 看
[root@node-1 cm]# kubectl describe cm nginx-nc
Name:         nginx-nc
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
nginx_port:
----
80
nginx_server:
----
erick.com
Events:  <none>
[root@node-1 cm]# kubectl describe cm nginx-cm-from-file
Name:         nginx-cm-from-file
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
www.conf:
----
server {
  server_name myapp.com;
  port 80;
  root /data/web/html;

}

Events:  <none>

可以看到用这种方式创建，key为文件名， key 为文件中的内容.

创建一个pod 关联刚刚创建的cm

[root@node-1 cm]# cat cm-1.yml 
apiVersion: v1
kind: Pod
metadata:
  name: myapp-cm-1
  namespace: default
  annotations:
    erick: "by erick"
spec:
  containers:
  - name: myapp-cm-1
    image: ikubernetes/myapp:v1
    ports:
    - name: http
      containerPort: 80
    env:
    - name: nginx_port
      valueFrom: 
        configMapKeyRef:
          name: nginx-nc
          key: nginx_port
    - name: nginx_server
      valueFrom: 
        configMapKeyRef:
          name: nginx-nc
          key: nginx_server

[root@node-1 cm]# 

进入容器并查看环境变量

[root@node-1 cm]# kubectl get pod
NAME                           READY   STATUS              RESTARTS   AGE
myapp-cm-1                     1/1     Running             0          2m16s
[root@node-1 cm]# kubectl exec -it myapp-cm-1 -- /bin/sh
/ # env|grep nginx_port
nginx_port=80
/ # env|grep nginx_server
nginx_server=erick.com
/ # 

我们把cm 的环境变量修改下

[root@node-1 cm]# kubectl edit  configmap  nginx-nc
# Please edit the object below. Lines beginning with a '#' will be ignored,
# and an empty file will abort the edit. If an error occurs while saving this file will be
# reopened with the relevant failures.
#
apiVersion: v1
data:
  nginx_port: "8080"
  nginx_server: erick.com
kind: ConfigMap
metadata:
  creationTimestamp: "2019-06-20T22:34:44Z"
  name: nginx-nc
  namespace: default
  resourceVersion: "436267"
  selfLink: /api/v1/namespaces/default/configmaps/nginx-nc
  uid: 9a180b6e-93ab-11e9-b0ae-080027edb92f
~                                          
把port修改成8080

再次查看环境变量是否更改
[root@node-1 cm]# kubectl exec -it myapp-cm-1 -- /bin/sh
/ # env|grep nginx_port
nginx_port=80
/ # 

结论： pod中的环境变量只会在第一次创建时生效，即使 重启pod也不会生效，后期修改不会生效。

2。基于存储卷的的 pod 引用环境变量。

apiVersion: v1
kind: Pod
metadata:
  name: myappcmwww
  namespace: default
  annotations:
    erick: "by erick"
spec:
  containers:
  - name: myappcmwww
    image: ikubernetes/myapp:v1
    ports:
    - name: http
      containerPort: 80
    volumeMounts:
    - name: nginx-conf
      mountPath: /etc/nginx/conf.d/
  volumes:
  - name: nginx-conf
    configMap:
      name: nginx-cm-from-file
[root@node-1 cm]# 

进入容器查看 环境变量
[root@node-1 cm]# kubectl exec -it myappcmwww -- /bin/sh
/ # cat /etc/nginx/conf.d/
..2019_06_22_09_11_04.278015527/  ..data/                           www.conf
/ # cat /etc/nginx/conf.d/www.conf 
server {
        server_name myapp.com;
        listen 80;
        root /data/web/html;

}
/ # 

修改configmap 的端口为8080

[root@node-1 ~]# kubectl edit cm nginx-cm-from-file
# Please edit the object below. Lines beginning with a '#' will be ignored,
# and an empty file will abort the edit. If an error occurs while saving this file will be
# reopened with the relevant failures.
#
apiVersion: v1
data:
  www.conf: "server {\n\tserver_name myapp.com;\n\tlisten 8080;\n\troot /data/web/html;\n\n}\n"
kind: ConfigMap
metadata:
  creationTimestamp: "2019-06-20T22:43:44Z"
  name: nginx-cm-from-file
  namespace: default
  resourceVersion: "494403"
  selfLink: /api/v1/namespaces/default/configmaps/nginx-cm-from-file
  uid: dbd2aa33-93ac-11e9-b0ae-080027edb92f

在容器内查看环境变量是否更改。
/ # cat /etc/nginx/conf.d/www.conf 
server {
        server_name myapp.com;
        listen 8080;
        root /data/web/html;

}
/ # 

已经动态的发生了改变。

secret
secret 是用base64 进行编码的格式

[root@node-1 cm]# kubectl create secret --help
[root@node-1 cm]# kubectl create secret --help
Create a secret using specified subcommand.

Available Commands:
  docker-registry Create a secret for use with a Docker registry ## 链接私有镜像时
  generic         Create a secret from a local file, directory or literal value  ## 储存密码时
  tls             Create a TLS secret ## 放入证书时

Usage:
  kubectl create secret [flags] [options]

Use "kubectl <command> --help" for more information about a given command.
Use "kubectl options" for a list of global command-line options (applies to all commands).
[root@node-1 cm]# 

secrete 是 用bash64 加密的， 可以被反向解密。