k8s概念-ConfigMap

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一般用于去存储 Pod 中应用所需的一些配置信息，或者环境变量，将配置于 Pod 分开，避免应为修改配置导致还需要重新构建 镜像与容器。

1 创建ConfigMap

#使用 kubectl create configmap -h 查看示例，构建 configmap 对象
Examples:
  # Create a new config map named my-config based on folder bar
  kubectl create configmap my-config --from-file=path/to/bar
  
  # Create a new config map named my-config with specified keys instead of file basenames on disk
  kubectl create configmap my-config --from-file=key1=/path/to/bar/file1.txt --from-file=key2=/path/to/bar/file2.txt
  
  # Create a new config map named my-config with key1=config1 and key2=config2
  kubectl create configmap my-config --from-literal=key1=config1 --from-literal=key2=config2
  
  # Create a new config map named my-config from the key=value pairs in the file
  kubectl create configmap my-config --from-file=path/to/bar
  
  # Create a new config map named my-config from an env file
  kubectl create configmap my-config --from-env-file=path/to/foo.env --from-env-file=path/to/bar.env

1.1 将指定目录下所有文件加载到配置文件中

# Create a new config map named my-config based on folder bar
# kubectl create configmap my-config --from-file=path/to/bar
#example:
#在test目录下有两个配置文件db.properties redis.properties

#1.创建configmap，名字为test-cm，从test目录下加载
[root@k8s-master1 configmap]# kubectl create cm test-cm --from-file=test/
configmap/test-cm created

#2.查看configmap
[root@k8s-master1 configmap]# kubectl get cm
NAME               DATA   AGE
kube-root-ca.crt   1      5d9h #k8s默认的认证
test-cm            2      7s	 #我们创建的

#3.查看test-cm的详细信息
[root@k8s-master1 configmap]# kubectl describe cm test-cm
#内容如下：
Name:         test-cm
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
db.properties:   #key
----
username: root
password: 1234

redis.properties:
----
port: 6379


BinaryData
====

Events:  <none>

1.2 指定一个或多个文件和key

# Create a new config map named my-config with specified keys instead of file basenames on disk
#  kubectl create configmap my-config --from-file=key1=/path/to/bar/file1.txt --from-file=key2=/path/to/bar/file2.txt

#指定一个或多个文件，不加key时以文件名作为key

#example：

#创建configmap，名称为testfile-cm，从指定的test目录下的db.properties加载
[root@k8s-master1 configmap]# kubectl create cm testfile-cm --from-file=test/db.properties
configmap/testfile-cm created

#查看configmap
[root@k8s-master1 configmap]# kubectl get cm
NAME               DATA   AGE
kube-root-ca.crt   1      5d10h
testfile-cm        1      5s

#查看详情
[root@k8s-master1 configmap]# kubectl describe cm testfile-cm
Name:         testfile-cm
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
db.properties: #不指定key，以文件名为key，如果指定则以具体指定作为key
----
username: root
password: 1234


BinaryData
====

Events:  <none>

1.3 命令上手动添加key-value

# Create a new config map named my-config with key1=config1 and key2=config2
#kubectl create configmap my-config --from-literal=key1=config1 --from-literal=key2=config2

#直接写入key和value

#example：

#创建configmap，名称为test-cm，手动添加key：user，value：root；key：password，value：1234
[root@k8s-master1 configmap]# kubectl create cm test-cm --from-literal=user=root --from-literal=password=1234
configmap/test-cm created
[root@k8s-master1 configmap]# kubectl get cm
NAME               DATA   AGE
kube-root-ca.crt   1      5d10h
test-cm            2      7s
[root@k8s-master1 configmap]# kubectl describe cm test-cm
Name:         test-cm
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
password: #key
----
1234   #value
user: #key
----
root  #value

BinaryData
====

Events:  <none>

2 configmap的使用

在pod中

• 将configmap中的数据设置为容器的环境变量

• 将ConfigMap中的数据设置为命令行参数

• 使用Volume将ConfigMap作为文件或目录挂载

• 编写代码在 Pod 中运行，使用 Kubernetes API 来读取 ConfigMap

将configmap挂载到容器中，configmap变化，容器自动更新

而 写入环境变量不会自动更新

2.1 配置到容器的环境变量中

# test-pod-configmap.yaml
apiVersion: v1
kind: Pod
metadata:
 name: test-pod-configmap
spec:
 containers:
  - name: test-busybox
    image: busybox
    imagePullPolicy: IfNotPresent
    args:
    - sleep
    - "86400"
    env:                  # env，配置容器环境变量
    - name: KEY1		  # 容器环境变量key为key1
      valueFrom:		  # value内容
       configMapKeyRef:	  # 通过configmap的key映射
        name: my-config	  # configmap的名称
        key: key1		  # configmap中的key
    - name: KEY2
      valueFrom:
       configMapKeyRef:
        name: my-config
        key: key2

2.2 设置为命令行参数

# test-pod-configmap-cmd
apiVersion: v1
kind: Pod
metadata:
 name: test-pod-configmap-cmd
spec:
 containers:
  - name: test-busybox
    image: busybox
    imagePullPolicy: IfNotPresent
    command: [ "/bin/sh","-c","echo $(KEY1) $(KEY2)"]
    env:
    - name: KEY1
      valueFrom:
       configMapKeyRef:
        name: my-config
        key: key1
    - name: KEY2
      valueFrom:
       configMapKeyRef:
        name: my-config
        key: key2
 restartPolicy: Never

2.3 将configmap挂载到容器中

# test-pod-projected-configmap-volume.yaml
apiVersion: v1
kind: Pod
metadata:
 name: test-pod-projected-configmap-volume
spec:
 containers:
 - name: test-pod-busybox
   image: busybox
   imagePullPolicy: IfNotPresent
   args:
   - sleep
   - "86400"
   volumeMounts:                        # 挂载
   - name: config-volume				# 挂载的数据卷名
     mountPath: "/projected-volume"		# 挂载到哪的路径
     readOnly: true						# 只读权限
 volumes:								# 数据卷
 - name: config-volume					# 数据卷名称
   projected:
    sources:
    - configMap:						# 数据卷为configmap
       name: my-config					# 数据卷名