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Kubernetes资源对象ConfigMap

著作：行癫 <盗版必究>

一：ConfigMap

用来存储配置文件的kubernetes资源对象，所有的配置内容都存储在etcd中；ConfigMap与 Secret 类似

1.ConfigMap与 Secret 的区别

ConfigMap 保存的是不需要加密的、应用所需的配置信息

ConfigMap 的用法几乎与 Secret 完全相同：可以使用 kubectl create configmap 从文件或者目录创建 ConfigMap，也可以直接编写 ConfigMap 对象的 YAML 文件

2.创建ConfigMap

方式1：通过直接在命令行中指定configmap参数创建，即--from-literal

方式2：通过指定文件创建，即将一个配置文件创建为一个ConfigMap--from-file=<文件>

方式3：通过指定目录创建，即将一个目录下的所有配置文件创建为一个ConfigMap，--from-file=<目录>

方式4：事先写好标准的configmap的yaml文件，然后kubectl create -f 创建

通过命令行参数--from-literal创建：

创建命令

[root@master yaml]# kubectl create configmap test-config1 --from-literal=db.host=10.5.10.116 --from-literal=db.port='3306'
configmap/test-config1 created

结果如下面的data内容所示

[root@master yaml]# kubectl get configmap test-config1 -o yaml
apiVersion: v1
data:
  db.host: 10.5.10.116
  db.port: "3306"
kind: ConfigMap
metadata:
  creationTimestamp: "2019-02-14T08:22:34Z"
  name: test-config1
  namespace: default
  resourceVersion: "7587"
  selfLink: /api/v1/namespaces/default/configmaps/test-config1
  uid: adfff64c-3031-11e9-abbe-000c290a5b8b

通过指定文件创建：

编辑配置文件app.properties内容如下

[root@master yaml]# cat app.properties 
property.1 = value-1
property.2 = value-2
property.3 = value-3
property.4 = value-4

[mysqld]
!include /home/wing/mysql/etc/mysqld.cnf
port = 3306
socket = /home/wing/mysql/tmp/mysql.sock
pid-file = /wing/mysql/mysql/var/mysql.pid
basedir = /home/mysql/mysql
datadir = /wing/mysql/mysql/var

创建（可以有多个--from-file）

[root@master yaml]# kubectl create configmap test-config2 --from-file=./app.properties

结果如下面data内容所示

[root@master yaml]# kubectl get configmap test-config2 -o yaml
apiVersion: v1
data:
  app.properties: |
    property.1 = value-1
    property.2 = value-2
    property.3 = value-3
    property.4 = value-4

    [mysqld]
    !include /home/wing/mysql/etc/mysqld.cnf
    port = 3306
    socket = /home/wing/mysql/tmp/mysql.sock
    pid-file = /wing/mysql/mysql/var/mysql.pid
    basedir = /home/mysql/mysql
    datadir = /wing/mysql/mysql/var
kind: ConfigMap
metadata:
  creationTimestamp: "2019-02-14T08:29:33Z"
  name: test-config2
  namespace: default
  resourceVersion: "8176"
  selfLink: /api/v1/namespaces/default/configmaps/test-config2
  uid: a8237769-3032-11e9-abbe-000c290a5b8b

通过指定文件创建时，configmap会创建一个key/value对，key是文件名，value是文件内容。如不想configmap中的key为默认的文件名，可以在创建时指定key名字

[root@master yaml]# kubectl create configmap game-config-3 --from-file=<my-key-name>=<path-to-file>

指定目录创建：

configs 目录下的config-1和config-2内容如下所示

[root@master yaml]# tail configs/config-1
aaa
bbb
c=d
[root@master yaml]# tail configs/config-2
eee
fff
h=k

创建

[root@master yaml]# kubectl create configmap test-config3 --from-file=./configs

结果下面data内容所示

[root@master yaml]# kubectl get configmap test-config3 -o yaml
apiVersion: v1
data:
  config-1: |
    aaa
    bbb
    c=d
  config-2: |
    eee
    fff
    h=k
kind: ConfigMap
metadata:
  creationTimestamp: "2019-02-14T08:37:05Z"
  name: test-config3
  namespace: default
  resourceVersion: "8808"
  selfLink: /api/v1/namespaces/default/configmaps/test-config3
  uid: b55ffbeb-3033-11e9-abbe-000c290a5b8b

指定目录创建时，configmap内容中的各个文件会创建一个key/value对，key是文件名，value是文件内容，忽略子目录

通过事先写好configmap的标准yaml文件创建：

yaml文件内容如下：注意其中一个key的value有多行内容时的写法

[root@master yaml]# cat configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: test-config4
  namespace: default
data:
  cache_host: memcached-gcxt
  cache_port: "11211"
  cache_prefix: gcxt
  my.cnf: |
   [mysqld]
   log-bin = mysql-bin
   haha = hehe

创建

[root@master yaml]# kubectl apply -f configmap.yaml 
configmap/test-config4 created

结果如下面data内容所示

[root@master yaml]# kubectl get configmap test-config4 -o yaml
apiVersion: v1
data:
  cache_host: memcached-gcxt
  cache_port: "11211"
  cache_prefix: gcxt
  my.cnf: |
    [mysqld]
    log-bin = mysql-bin
    haha = hehe
kind: ConfigMap
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"v1","data":{"cache_host":"memcached-gcxt","cache_port":"11211","cache_prefix":"gcxt","my.cnf":"[mysqld]\nlog-bin = mysql-bin\nhaha = hehe\n"},"kind":"ConfigMap","metadata":{"annotations":{},"name":"test-config4","namespace":"default"}}
  creationTimestamp: "2019-02-14T08:46:57Z"
  name: test-config4
  namespace: default
  resourceVersion: "9639"
  selfLink: /api/v1/namespaces/default/configmaps/test-config4
  uid: 163fbe1e-3035-11e9-abbe-000c290a5b8b

查看configmap的详细信息

[root@master yaml]# kubectl describe configmap

3.使用ConfigMap

通过环境变量的方式，直接传递pod

通过在pod的命令行下运行的方式

使用volume的方式挂载入到pod内

示例ConfigMap文件：

apiVersion: v1
kind: ConfigMap
metadata:
  name: special-config
  namespace: default
data:
  special.how: very
  special.type: charm

通过环境变量使用：

使用valueFrom、configMapKeyRef、name、key指定要用的key

[root@master yaml]# cat testpod.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: dapi-test-pod
spec:
  containers:
    - name: test-container
      image: daocloud.io/library/nginx
      env:
        - name: SPECIAL_LEVEL_KEY   //这里是容器里设置的新变量的名字
          valueFrom:
            configMapKeyRef:
              name: special-config    //这里是来源于哪个configMap
              key: special.how           //configMap里的key
        - name: SPECIAL_TYPE_KEY
          valueFrom:
            configMapKeyRef:
              name: special-config
              key: special.type
  restartPolicy: Never

测试

[root@master yaml]# kubectl exec -it dapi-test-pod /bin/bash
root@dapi-test-pod:/# echo $SPECIAL_TYPE_KEY
charm

通过envFrom、configMapRef、name使得configmap中的所有key/value对都自动变成环境变量

apiVersion: v1
kind: Pod
metadata:
  name: dapi-test-pod
spec:
  containers:
    - name: test-container
      image: daocloud.io/library/nginx
      envFrom:
      - configMapRef:
          name: special-config
  restartPolicy: Never

这样容器里的变量名称直接使用configMap里的key名

[root@master yaml]# kubectl exec -it dapi-test-pod /bin/bash
root@dapi-test-pod:/# env  
HOSTNAME=dapi-test-pod
NJS_VERSION=1.15.8.0.2.7-1~stretch
NGINX_VERSION=1.15.8-1~stretch
KUBERNETES_PORT_443_TCP_PROTO=tcp
KUBERNETES_PORT_443_TCP_ADDR=10.96.0.1
KUBERNETES_PORT=tcp://10.96.0.1:443
PWD=/
special.how=very
HOME=/root
KUBERNETES_SERVICE_PORT_HTTPS=443
KUBERNETES_PORT_443_TCP_PORT=443
KUBERNETES_PORT_443_TCP=tcp://10.96.0.1:443
TERM=xterm
SHLVL=1
KUBERNETES_SERVICE_PORT=443
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
special.type=charm
KUBERNETES_SERVICE_HOST=10.96.0.1

作为volume挂载使用：

apiVersion: apps/v1 
kind: Deployment
metadata:
  name: nginx-configmap
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx-configmap
        image: daocloud.io/library/nginx:latest
        ports:
        - containerPort: 80
        volumeMounts:     
        - name: config-volume3
          mountPath: /tmp/config3
      volumes:
      - name: config-volume3
        configMap:
          name: test-config-3

进入容器中/tmp/config4查看

[root@master yaml]# kubectl  exec -it nginx-configmap-7447bf77d6-svj2t /bin/bash

root@nginx-configmap-7447bf77d6-svj2t:/# ls /tmp/config4/
cache_host  cache_port	cache_prefix  my.cnf

root@nginx-configmap-7447bf77d6-svj2t:/# cat /tmp/config4/cache_host 
memcached-gcxt

可以看到，在config4文件夹下以每一个key为文件名value为值创建了多个文件。

假如不想以key名作为配置文件名可以引入items 字段，在其中逐个指定要用相对路径path替换的key：

     volumes:
      - name: config-volume4
        configMap:
          name: test-config4
          items:
          - key: my.cnf    //原来的key名
            path: mysql-key
          - key: cache_host   //原来的key名
            path: cache-host

注意：

删除configmap后原pod不受影响；然后再删除pod后，重启的pod的events会报找不到cofigmap的volume

pod起来后再通过kubectl edit configmap …修改configmap，过一会pod内部的配置也会刷新

在容器内部修改挂进去的配置文件后，过一会内容会再次被刷新为原始configmap内容

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