DevOps技术

# 一、ConfigMap实例演示
ConfigMap是一种比较特殊的存储卷，它的主要作用是用来存储配置信息的
## 1.1 创建configmap
编写configmap.yaml文件，内容如下：
```yaml
apiVersion: v1
kind: Namespace
metadata:
  name: dev

---

apiVersion: v1
kind: ConfigMap
metadata:
  name: configmap
  namespace: dev
data:
  info: |
    username: admin
    password: admin123
```
然后使用如下命令创建configmap
```bash
[root@master volume]# kubectl apply -f configmap.yaml
namespace/dev created
configmap/configmap created
[root@master volume]#
```
查看创建的configmap
```bash
[root@master volume]# kubectl get configmap -n dev
NAME               DATA   AGE
configmap          1      43s
[root@master volume]# 
```
通过如下命令查看configmap的详细信息
```bash
[root@master volume]# kubectl describe configmap configmap -n dev
Name:         configmap
Namespace:    dev
Labels:       <none>
Annotations:  <none>

Data
====
info:
----
username: admin
password: admin123

Events:  <none>
[root@master volume]#
```
## 1.2 configmap挂载到pod上
编辑pod_configmap.yaml文件，内容如下：
```yaml
apiVersion: v1
kind: Pod
metadata:
  name: pod-configmap
  namespace: dev
spec:
  containers:
  - name: nginx
    image: nginx:1.17.1
    volumeMounts:
    - name: config
      mountPath: /configmap/config
  volumes:
  - name: config
    configMap:
      name: configmap
```
使用如下命令创建pod
```bash
[root@master volume]# kubectl apply -f pod_configmap.yaml
pod/pod-configmap created
[root@master volume]#
```
查看创建pod资源
```bash
[root@master volume]# kubectl get pod -n dev
NAME            READY   STATUS    RESTARTS   AGE
pod-configmap   1/1     Running   0          4m29s
[root@master volume]#
```
如下进入pod中，查看挂载到的配置文件
```bash
[root@master volume]# kubectl exec -it pod-configmap -n dev /bin/sh
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
# cd /configmap/config
# ls
info
# cat info
username: admin
password: admin123
#
```
## 1.3 configmap实现动态更新
编辑configmap.yaml文件，如下，将密码修改为123456
```yaml
apiVersion: v1
kind: Namespace
metadata:
  name: dev

---

apiVersion: v1
kind: ConfigMap
metadata:
  name: configmap
  namespace: dev
data:
  info: |
    username: admin
    password: 123456
```
然后使用如下命令更新configmap
```bash
[root@master volume]# kubectl apply -f configmap.yaml
namespace/dev unchanged
configmap/configmap configured
[root@master volume]#
```
稍微等一会，然后继续查看pod中的info文件中的内容，发现此时已经更新了
```bash
# cat info
username: admin
password: 123456
#
```
至此，configmap即完成了配置文件的动态更新

不积跬步，无以至千里

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