Kubernetes之ConfigMap和Secret

Posted wlbl

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Kubernetes之ConfigMap和Secret

简介
ConfigMap和Secret是kubernetes系统上两种特殊类型的存储卷,ConfigMao对象用于为容器中的应用提供配置数据以定制程序行为,不过年敏感的配置信息,例如密钥,证书等通常由Secret对象来进行配置,它们将相应的配置信息保存于对象中,而后在Pod资源上以存储卷的形式将其挂载并获取相关配置,以实现配置与镜像文件的解耦。

传统的实践过程中们需要对一个应用进行配置,只需要修改其配置文件通常有以下几种方式:

  • 启动容器时,通过命令传递参数 command args自定义参数
  • 把配置文件写入镜像内
  • 通过环境变量的方式传递配置数据
    • cloud native的程序,一般通过环境变量加载配置
    • 通过enteypoint脚本预处理变量为配置文件中的配置信息
  • 挂载Docker卷传送配置文件

而在Kubernetes系统之中也存在这样的组件,就是特殊的存储卷类型。其并不是提供pod存储空间,而是给管理员或用户提供从集群外部向Pod内部的应用注入配置信息的方式。这两种特殊类型的存储卷:configMap和secret

ConfigMap:主要用于向Pod注入非敏感数据,使用时,用户将数据直接存储在ConfigMap对象当中,然后Pod通过使用ConfigMap卷进行引用,实现容器的配置文件集中定义和管理。
Secret:用于向Pod传递敏感信息,比如密码,私钥,证书文件等,这些信息如果在容器中定义容易泄露,Secret资源可以让用户将这些信息存储在急群众,然后通过Pod进行挂载,实现敏感数据和系统解耦的效果。

ConfigMap

configmap是让配置文件从镜像中解耦,让镜像的可移植性和可复制性。许多应用程序会从配置文件、命令行参数或环境变量中读取配置信息。这些配置信息需要与docker image解耦,ConfigMap API给我们提供了向容器中注入配置信息的机制,ConfigMap可以被用来保存单个属性,也可以用来保存整个配置文件或者JSON二进制对象。

ConfigMap API资源用来保存key-value pair配置数据,这个数据可以在pods里使用,或者被用来为像controller一样的系统组件存储配置数据。虽然ConfigMap跟Secrets类似,但是ConfigMap更方便的处理不含敏感信息的字符串。 注意:ConfigMaps不是属性配置文件的替代品。ConfigMaps只是作为多个properties文件的引用。可以把它理解为Linux系统中的/etc目录,专门用来存储配置文件的目录。下面举个例子,使用ConfigMap配置来创建Kuberntes Volumes,ConfigMap中的每个data项都会成为一个新文件。

[[email protected] ~]# kubectl explain cm.
KIND:     ConfigMap
VERSION:  v1

FIELDS:
   apiVersion   <string>

   data <map[string]string>

   kind <string>

   metadata     <Object>

ConfigMap创建方式

1、 通过 --from-literal:

[[email protected] configmap]# kubectl create configmap nginx-config --from-literal=nginx_port=8080 --from-literal=server_name=myapp.white.com
configmap/nginx-config created
[[email protected] configmap]# kubectl get cm
NAME           DATA   AGE
nginx-config   2      4s

[[email protected] configmap]# kubectl describe cm nginx-config 
Name:         nginx-config
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
nginx_port:
----
8080
server_name:
----
myapp.white.com
Events:  <none>

2、通过 --from-file:

[[email protected] configmap]# vim www.conf
server {
        server_name myapp.white.com;
        listen 80;
        root /data/web/html/;
}


[[email protected] configmap]# kubectl create configmap nginx-www --from-file=./www.conf 
configmap/nginx-www created
[[email protected] configmap]# kubectl get cm
NAME           DATA   AGE
nginx-config   2      3m5s
nginx-www      1      3s
[[email protected] configmap]# kubectl get cm nginx-www -o yaml
apiVersion: v1
data:
  www.conf: "server {\\n\\tserver_name myapp.white.com;\\n\\tlisten 80;\\n\\troot /data/web/html/;\\n}\\n"
kind: ConfigMap
metadata:
  creationTimestamp: "2019-04-03T02:25:57Z"
  name: nginx-www
  namespace: default
  resourceVersion: "207536"
  selfLink: /api/v1/namespaces/default/configmaps/nginx-www
  uid: d0171cb8-55b7-11e9-80a7-000c295ec349

将cm注入到pod内

[[email protected] configmap]# vim pod-configmap.yaml
apiVersion: v1
kind: Pod
metadata:
  name: pod-cm-1
  namespace: default
  labels:
    app: myapp
    tier: frontend
spec:
  containers:
  - name: myapp
    image: ikubernetes/myapp:v1
    ports:
    - name: http
      containerPort: 80
    env:
    - name: NGINX_SERVER_PORT
      valueFrom:
        configMapKeyRef:
          name: nginx-config
          key: nginx_port
    - name: NGINX_SERVER_NAME
      valueFrom:
        configMapKeyRef:
          name: nginx-config
          key: server_name

[[email protected] configmap]# kubectl get pods
NAME                                 READY   STATUS    RESTARTS   AGE
myapp-backend-pod-6b56d98b6b-2dh5h   1/1     Running   0          25h
myapp-backend-pod-6b56d98b6b-hwzws   1/1     Running   0          25h
myapp-backend-pod-6b56d98b6b-ztwn2   1/1     Running   0          25h
pod-cm-1                             1/1     Running   0          19s
pod-hostpath-vol                     1/1     Running   0          20h
pod-pvc-vol                          1/1     Running   0          17h
tomcat-deploy-5f554cd88d-7gzc7       1/1     Running   0          24h
tomcat-deploy-5f554cd88d-c42t6       1/1     Running   0          24h
tomcat-deploy-5f554cd88d-qhc4j       1/1     Running   0          24h

进入容器查看:

[[email protected] configmap]# kubectl exec -it pod-cm-1  -- /bin/sh
/ # printenv
MYAPP_SVC_PORT_80_TCP_ADDR=10.98.57.156
KUBERNETES_SERVICE_PORT=443
KUBERNETES_PORT=tcp://10.96.0.1:443
MYAPP_SERVICE_PORT_HTTP=80
TOMCAT_PORT_8080_TCP=tcp://10.107.88.118:8080
TOMCAT_PORT_8009_TCP=tcp://10.107.88.118:8009
MYAPP_SVC_PORT_80_TCP_PORT=80
HOSTNAME=pod-cm-1
SHLVL=1
MYAPP_SVC_PORT_80_TCP_PROTO=tcp
HOME=/root
MYAPP_SERVICE_HOST=10.100.41.152
NGINX_SERVER_PORT=8080   #已经被调用
NGINX_SERVER_NAME=myapp.white.com   #已经被调用
MYAPP_SVC_PORT_80_TCP=tcp://10.98.57.156:80
MYAPP_PORT=tcp://10.100.41.152:80
MYAPP_SERVICE_PORT=80
TERM=xterm
NGINX_VERSION=1.12.2
KUBERNETES_PORT_443_TCP_ADDR=10.96.0.1
MYAPP_PORT_80_TCP_ADDR=10.100.41.152
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
TOMCAT_SERVICE_PORT_HTTP=8080
KUBERNETES_PORT_443_TCP_PORT=443
KUBERNETES_PORT_443_TCP_PROTO=tcp
MYAPP_PORT_80_TCP_PORT=80
MYAPP_PORT_80_TCP_PROTO=tcp
MYAPP_SVC_SERVICE_HOST=10.98.57.156
TOMCAT_PORT_8080_TCP_ADDR=10.107.88.118
TOMCAT_SERVICE_HOST=10.107.88.118
TOMCAT_PORT_8009_TCP_ADDR=10.107.88.118
KUBERNETES_SERVICE_PORT_HTTPS=443
KUBERNETES_PORT_443_TCP=tcp://10.96.0.1:443
TOMCAT_PORT_8080_TCP_PORT=8080
PWD=/
KUBERNETES_SERVICE_HOST=10.96.0.1
MYAPP_PORT_80_TCP=tcp://10.100.41.152:80
TOMCAT_PORT_8080_TCP_PROTO=tcp
TOMCAT_PORT_8009_TCP_PORT=8009
MYAPP_SVC_SERVICE_PORT=80
MYAPP_SVC_PORT=tcp://10.98.57.156:80
TOMCAT_PORT_8009_TCP_PROTO=tcp
TOMCAT_PORT=tcp://10.107.88.118:8080
TOMCAT_SERVICE_PORT=8080
TOMCAT_SERVICE_PORT_AJP=8009

如果此时使用kubectl edit cm来修改configmap 此时在容器内查看环境变量不会被修改,因为该env是在pod创建的时候获取的,不会被修改

存储卷方式挂载configmap

[[email protected] configmap]# vim pod-configmap-2.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: pod-cm-2
  namespace: default
  labels:
    app: myapp
    tier: frontend
spec:
  containers:
  - name: myapp
    image: ikubernetes/myapp:v1
    ports:
    - name: http
      containerPort: 80
    volumeMounts:
    - name: nginxconf
      mountPath: /etc/nginx/config.d/
      readOnly: true
  volumes:
  - name: nginxconf
    configMap:
      name: nginx-config


[[email protected] configmap]# kubectl apply -f pod-configmap-2.yaml 
pod/pod-cm-2 created

查看并进入Pod

[[email protected] configmap]# kubectl get pods
NAME                                 READY   STATUS    RESTARTS   AGE
myapp-backend-pod-6b56d98b6b-2dh5h   1/1     Running   0          29h
myapp-backend-pod-6b56d98b6b-hwzws   1/1     Running   0          29h
myapp-backend-pod-6b56d98b6b-ztwn2   1/1     Running   0          29h
pod-cm-2                             1/1     Running   0          53s
pod-hostpath-vol                     1/1     Running   0          23h
pod-pvc-vol                          1/1     Running   0          20h
tomcat-deploy-5f554cd88d-7gzc7       1/1     Running   0          27h
tomcat-deploy-5f554cd88d-c42t6       1/1     Running   0          27h
tomcat-deploy-5f554cd88d-qhc4j       1/1     Running   0          27h

[[email protected] configmap]# kubectl exec -it pod-cm-2 -- /bin/sh
/ # cd /etc/nginx/config.d/
/etc/nginx/config.d # ls
nginx_port   server_name
/etc/nginx/config.d # cat nginx_port
8080
/etc/nginx/config.d # cat server_name
myapp.white.com/etc/nginx/config.d 

此时使用kubectl edit修改端口,进入容器进行查看

[[email protected] ~]# kubectl edit cm nginx-config 

# 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: "11111"
  server_name: myapp.white.com
kind: ConfigMap
metadata:
  creationTimestamp: "2019-04-03T02:22:55Z"
  name: nginx-config
  namespace: default
  resourceVersion: "207257"
  selfLink: /api/v1/namespaces/default/configmaps/nginx-config
  uid: 63e91046-55b7-11e9-80a7-000c295ec349

进入容器查看(需要等待一小会,有一定延迟时间)

/etc/nginx/config.d # cat nginx_port 
11111
/etc/nginx/config.d #

使用nginx-www配置nginx

nginx-www是使用文件创建的cm,文件名是键名,内容是值。

[[email protected] configmap]# vim pod-configmap-3.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: pod-cm-3
  namespace: default
  labels:
    app: myapp
    tier: frontend
spec:
  containers:
  - name: myapp
    image: ikubernetes/myapp:v1
    ports:
    - name: http
      containerPort: 80
    volumeMounts:
    - name: nginxconf
      mountPath: /etc/nginx/conf.d/
      readOnly: true
  volumes:
  - name: nginxconf
    configMap:
      name: nginx-www

创建并查看

[[email protected] configmap]# kubectl apply -f pod-configmap-3.yaml
pod/pod-cm-3 created
[[email protected] configmap]# kubectl get pods
NAME                                 READY   STATUS    RESTARTS   AGE
myapp-backend-pod-6b56d98b6b-2dh5h   1/1     Running   0          29h
myapp-backend-pod-6b56d98b6b-hwzws   1/1     Running   0          29h
myapp-backend-pod-6b56d98b6b-ztwn2   1/1     Running   0          29h
pod-cm-3                             1/1     Running   0          5s
pod-hostpath-vol                     1/1     Running   0          23h
pod-pvc-vol                          1/1     Running   0          20h
tomcat-deploy-5f554cd88d-7gzc7       1/1     Running   0          28h
tomcat-deploy-5f554cd88d-c42t6       1/1     Running   0          28h
tomcat-deploy-5f554cd88d-qhc4j       1/1     Running   0          28h

进入容器查看

[[email protected] configmap]# kubectl exec -it pod-cm-3 -- /bin/sh 
/ # cd /etc/nginx/conf.d/
/etc/nginx/conf.d # ls
www.conf
/etc/nginx/conf.d # cat www.conf 
server {
        server_name myapp.white.com;
        listen 80;
        root /data/web/html/;
}

查看nginx加载的内容
/etc/nginx/conf.d # nginx -T
... ...
# configuration file /etc/nginx/conf.d/www.conf:
server {
        server_name myapp.white.com;
        listen 80;
        root /data/web/html/;
}

此时使用kubectl edit修改cm内的内容,容器内部会被修改,但是nginx 需要重载才能生效,如果需要这样配置,需要手动或配置脚本进行nginx -s reload。

Secret

Secret对象存储数据的方式是以键值方式存储数据,在Pod资源进行调用Secret的方式是通过环境变量或者存储卷的方式进行访问数据,解决了密码、token、密钥等敏感数据的配置问题,而不需要把这些敏感数据暴露到镜像或者Pod Spec中。另外,Secret对象的数据存储和打印格式为Base64编码的字符串,因此用户在创建Secret对象时,也需要提供该类型的编码格式的数据。在容器中以环境变量或存储卷的方式访问时,会自动解码为明文格式。需要注意的是,如果是在Master节点上,Secret对象以非加密的格式存储在etcd中,所以需要对etcd的管理和权限进行严格控制。
Secret有4种类型:

  • Service Account :用来访问Kubernetes API,由Kubernetes自动创建,并且会自动挂载到Pod的/run/secrets/kubernetes.io/serviceaccount目录中;
  • Opaque :base64编码格式的Secret,用来存储密码、密钥、信息、证书等,类型标识符为generic;
  • kubernetes.io/dockerconfigjson :用来存储私有docker registry的认证信息,类型标识为docker-registry。
  • kubernetes.io/tls:用于为SSL通信模式存储证书和私钥文件,命令式创建类型标识为tls。

创建 Secret

使用--from-literal

[[email protected] configmap]# kubectl create secret generic mysql-root-password [email protected]
secret/mysql-root-password created
[[email protected] configmap]# kubectl get secret
NAME                    TYPE                                  DATA   AGE
default-token-dqd2f     kubernetes.io/service-account-token   3      6d22h
mysql-root-password     Opaque                                1      4s
tomcat-ingress-secret   kubernetes.io/tls                     2      28h

查看

[[email protected] configmap]# kubectl describe secret mysql-root-password
Name:         mysql-root-password
Namespace:    default
Labels:       <none>
Annotations:  <none>

Type:  Opaque

Data
====
password:  9 bytes

查看可知只有9个字节,没有显示内容。可以转换成YAML格式文件查看Base64加密后的password

[[email protected] configmap]# kubectl describe secret mysql-root-password
Name:         mysql-root-password
Namespace:    default
Labels:       <none>
Annotations:  <none>

Type:  Opaque

Data
====
password:  9 bytes
[[email protected] configmap]# kubectl get secret mysql-root-password -o yaml
apiVersion: v1
data:
  password: TXlQQHNzMTIz
kind: Secret
metadata:
  creationTimestamp: "2019-04-03T06:46:00Z"
  name: mysql-root-password
  namespace: default
  resourceVersion: "226351"
  selfLink: /api/v1/namespaces/default/secrets/mysql-root-password
  uid: 247548a3-55dc-11e9-80a7-000c295ec349
type: Opaque

解码

[[email protected] configmap]# echo TXlQQHNzMTIz|base64 -d
[email protected]

使用--from-file

[[email protected] configmap]# echo -n admin > ./username
[[email protected] configmap]#  echo -n 123456 > ./password
[[email protected] configmap]# kubectl create secret generic mysecret --from-file=./username --from-file=./password 
secret/mysecret created
[[email protected] configmap]# kubectl get secret
NAME                    TYPE                                  DATA   AGE
default-token-dqd2f     kubernetes.io/service-account-token   3      6d22h
mysecret                Opaque                                2      4s
mysql-root-password     Opaque                                1      6m6s
tomcat-ingress-secret   kubernetes.io/tls                     2      28h

通过 --from-env-file

文件 env.txt 中每行 Key=Value 对应一个信息条目。

[[email protected] configmap]# vim pod-secret-1.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: pod-secret-1
  namespace: default
  labels:
    app: myapp
    tier: frontend
spec:
  containers:
  - name: myapp
    image: ikubernetes/myapp:v1
    ports:
    - name: http
      containerPort: 80
    env:
    - name: MYSQL_ROOT_PASSWORD
      valueFrom:
        secretKeyRef:
          name: mysql-root-password
          key: password


[[email protected] configmap]# kubectl apply -f pod-secret-1.yaml 
pod/pod-secret-1 created

进入Pod查看

[[email protected] configmap]# kubectl exec -it pod-secret-1 -- /bin/sh
/ # printenv|grep MYSQL_ROOT_PASSWORD
[email protected]

在Pod内已经是转换后的密码,任何人都可以看到,不够安全。

使用挂在存储卷方式

[[email protected] configmap]# kubectl get secret
NAME                    TYPE                                  DATA   AGE
default-token-dqd2f     kubernetes.io/service-account-token   3      6d22h
mysecret                Opaque                                2      11m
mysql-root-password     Opaque                                1      17m
tomcat-ingress-secret   kubernetes.io/tls                     2      28h

[[email protected] configmap]# vim pod-secret-demo.yaml
apiVersion: v1
kind: Pod
metadata:
  name: pod-secret-vol
spec:
  containers:
  - name: pod-secret-vol
    image: busybox
    args:
    - /bin/sh
    - -c
    - sleep 10;touch /tmp/healthy;sleep 36000
    volumeMounts:
    - name: test
      mountPath: "/etc/test"
      readOnly: true
  volumes:
  - name: test
    secret:
      secretName: mysecret

[[email protected] configmap]# kubectl apply -f pod-secret-demo.yaml 
pod/pod-secret-vol created

[[email protected] configmap]# kubectl get pods
NAME                                 READY   STATUS    RESTARTS   AGE
myapp-backend-pod-6b56d98b6b-2dh5h   1/1     Running   0          30h
myapp-backend-pod-6b56d98b6b-hwzws   1/1     Running   0          30h
myapp-backend-pod-6b56d98b6b-ztwn2   1/1     Running   0          30h
pod-hostpath-vol                     1/1     Running   0          24h
pod-pvc-vol                          1/1     Running   0          21h
pod-secret-1                         1/1     Running   0          9m
pod-secret-vol                       1/1     Running   0          7s
tomcat-deploy-5f554cd88d-7gzc7       1/1     Running   0          29h
tomcat-deploy-5f554cd88d-c42t6       1/1     Running   0          29h
tomcat-deploy-5f554cd88d-qhc4j       1/1     Running   0          29h

进入Pod查看

[[email protected] configmap]# kubectl exec -it pod-secret-vol -- /bin/sh
/ # cd /etc/test/
/etc/test # ls
password  username
/etc/test # cat username
admin
/etc/test # cat password
123456

可以看到,Kubernetes 会在指定的路径 /etc/test 下为每条敏感数据创建一个文件,文件名就是数据条目的 Key,这里是 /etc/test/username 和 /etc/test/password,Value 则以明文存放在文件中。
也可以自定义存放数据的文件名,比如将配置文件改为:

[[email protected] configmap]# vim  pod-secret-damo-1.yaml
apiVersion: v1
kind: Pod
metadata:
  name: pod-secret-vol-1
spec:
  containers:
  - name: pod-secret-vol-1
    image: busybox
    args:
    - /bin/sh
    - -c
    - sleep 10;touch /tmp/healthy;sleep 36000
    volumeMounts:
    - name: test
      mountPath: "/etc/test"
      readOnly: true
  volumes:
  - name: test
    secret:
      secretName: mysecret
      items:
      - key: username
        path: my-secret/my-username
      - key: password
        path: my-secret/my-password

这时数据将分别存放在 /etc/test/my-secret/my-username 和 /etc/test/my-secret/my-password 中。

[[email protected] configmap]# kubectl exec -it pod-secret-vol-1 -- /bin/sh
/ # cd /etc/test/
/etc/test # ls
my-secret
/etc/test # cd my-secret/
/etc/test/..2019_04_03_07_12_02.941048565/my-secret # ls
my-password  my-username
/etc/test/..2019_04_03_07_12_02.941048565/my-secret # cat  my-username
admin
/etc/test/..2019_04_03_07_12_02.941048565/my-secret # cat my-password
123456

以 Volume 方式使用的 Secret 支持动态更新:Secret 更新后,容器中的数据也会更新。
将 password 更新为 abcdef,base64 编码为 YWJjZGVm

[[email protected] configmap]#  vim secret.yaml
apiVersion: v1
kind: Secret
metadata:
  name: mysecret
data:
  username: YWRtaW4=   #echo -n  admin|base64
  password: YWJjZGVm   #echo -n   abcdef|base64


[[email protected] configmap]# kubectl exec -it pod-secret-vol-1 -- /bin/sh
/etc # cd test/my-secret/
/etc/test/..2019_04_03_07_18_09.073816450/my-secret # ls
my-password  my-username
/etc/test/..2019_04_03_07_18_09.073816450/my-secret # cat my-password 
abcdef

通过 Volume 使用 Secret,容器必须从文件读取数据,会稍显麻烦,Kubernetes 还支持通过环境变量使用 Secret。

[[email protected] configmap]# vim pod-secret-env-demo.yaml
apiVersion: v1
kind: Pod
metadata:
  name: pod-secret-env
spec:
  containers:
  - name: pod-secret-env
    image: busybox
    args:
    - /bin/sh
    - -c
    - sleep 10;touch /tmp/healthy;sleep 36000
    env:
      - name: SECRET_USERNAME
        valueFrom:
          secretKeyRef:
            name: mysecret
            key: username
      - name: SECRET_PASSWORD
        valueFrom:
          secretKeyRef:
            name: mysecret
            key: password


[[email protected] configmap]# kubectl apply -f pod-secret-env-demo.yaml
pod/pod-secret-env created

[[email protected] configmap]# kubectl exec -it pod-secret-env sh
/ #  echo $SECRET_USERNAME
admin
/ # echo $SECRET_PASSWORD
abcdef

总结:
通过环境变量 SECRET_USERNAME 和 SECRET_PASSWORD 成功读取到 Secret 的数据。
需要注意的是,环境变量读取 Secret 很方便,但不支持Secret 动态更新。

参考资料

https://www.cnblogs.com/linuxk
马永亮. Kubernetes进阶实战 (云计算与虚拟化技术丛书)
Kubernetes-handbook-jimmysong-20181218

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