Kubernetes 101

    等到容器变成 Running 后，就可以用 kubectl 命令来操作它了，比如

    • kubectl get - 类似于 docker ps，查询资源列表
    • kubectl describe - 类似于 docker inspect，获取资源的详细信息
    • kubectl logs - 类似于 docker logs，获取容器的日志
    • kubectl exec - 类似于 docker exec，在容器内执行一个命令
    1. $ kubectl get pods
    2. NAME                         READY     STATUS    RESTARTS   AGE
    3. nginx-app-4028413181-cnt1i   1/1       Running   0          6m
    5. $ kubectl exec nginx-app-4028413181-cnt1i ps aux
    6. USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
    7. root         1  0.0  0.5  31736  5108 ?        Ss   00:19   0:00 nginx: master process nginx -g daemon off;
    8. nginx        5  0.0  0.2  32124  2844 ?        S    00:19   0:00 nginx: worker process
    9. root        18  0.0  0.2  17500  2112 ?        Rs   00:25   0:00 ps aux
    11. $ kubectl describe pod nginx-app-4028413181-cnt1i
    12. Name:          nginx-app-4028413181-cnt1i
    13. Namespace:         default
    14. Node:          boot2docker/192.168.64.12
    15. Start Time:        Tue, 06 Sep 2016 08:18:41 +0800
    16. Labels:        pod-template-hash=4028413181
    17.                run=nginx-app
    18. Status:        Running
    19. IP:            172.17.0.3
    20. Controllers:       ReplicaSet/nginx-app-4028413181
    21. Containers:
    22.   nginx-app:
    23.     Container ID:              docker://4ef989b57d0a7638ad9c5bbc22e16d5ea5b459281c77074fc982eba50973107f
    24.     Image:                 nginx
    25.     Image ID:              docker://sha256:4efb2fcdb1ab05fb03c9435234343c1cc65289eeb016be86193e88d3a5d84f6b
    26.     Port:                  80/TCP
    27.     State:                 Running
    28.       Started:             Tue, 06 Sep 2016 08:19:30 +0800
    29.     Ready:                 True
    30.     Restart Count:             0
    31.     Environment Variables:         <none>
    32. Conditions:
    33.   Type         Status
    34.   Initialized      True
    35.   Ready            True
    37. Volumes:
    38.   default-token-9o8ks:
    39.     Type:          Secret (a volume populated by a Secret)
    40.     SecretName:    default-token-9o8ks
    41. Events:
    42.   FirstSeen        LastSeen           Count      From               SubobjectPath              Type           Reason         Message
    43.   ---------        --------           -----      ----               -------------              --------           ------         -------
    44.   8m           8m             1          {default-scheduler}                       Normal         Scheduled          Successfully assigned nginx-app-4028413181-cnt1i to boot2docker
    45.   8m           8m             1          {kubelet boot2docker}      spec.containers{nginx-app}         Normal         Pulling        pulling image "nginx"
    46.   7m           7m             1          {kubelet boot2docker}      spec.containers{nginx-app}         Normal         Pulled         Successfully pulled image "nginx"
    47.   7m           7m             1          {kubelet boot2docker}      spec.containers{nginx-app}         Normal         Created        Created container with docker id 4ef989b57d0a
    48.   7m           7m             1          {kubelet boot2docker}      spec.containers{nginx-app}         Normal         Started        Started container with docker id 4ef989b57d0a
    50. $ curl http://172.17.0.3
    51. <!DOCTYPE html>
    52. <html>
    53. <head>
    54. <title>Welcome to nginx!</title>
    55. <style>
    56.     body {
    57.         width: 35em;
    58.         margin: 0 auto;
    59.         font-family: Tahoma, Verdana, Arial, sans-serif;
    60.     }
    61. </style>
    62. </head>
    63. <body>
    64. <h1>Welcome to nginx!</h1>
    65. <p>If you see this page, the nginx web server is successfully installed and
    66. working. Further configuration is required.</p>
    67. <p>For online documentation and support please refer to
    68. <a href="http://nginx.org/">nginx.org</a>.<br/>
    69. Commercial support is available at
    70. <a href="http://nginx.com/">nginx.com</a>.</p>
    71. <p><em>Thank you for using nginx.</em></p>
    72. </body>
    73. </html>
    75. $ kubectl logs nginx-app-4028413181-cnt1i
    76. 127.0.0.1 - - [06/Sep/2016:00:27:13 +0000] "GET / HTTP/1.0" 200 612 "-" "-" "-"

    前面提到，kubectl run 并不是直接创建一个 Pod，而是先创建一个 Deployment 资源（replicas=1），再由与 Deployment 关联的 ReplicaSet 来自动创建 Pod，这等价于这样一个配置：

    2. kind: Deployment
    3. metadata:
    4.   labels:
    5.     run: nginx-app
    6.   name: nginx-app
    7.   namespace: default
    8. spec:
    9.   replicas: 1
    10.   selector:
    11.     matchLabels:
    12.   strategy:
    13.     rollingUpdate:
    14.       maxSurge: 1
    15.       maxUnavailable: 1
    16.     type: RollingUpdate
    17.   template:
    18.     metadata:
    19.       labels:
    20.         run: nginx-app
    21.     spec:
    22.       containers:
    23.       - image: nginx
    24.         name: nginx-app
    25.         ports:
    26.         - containerPort: 80
    27.           protocol: TCP
    28.       dnsPolicy: ClusterFirst
    29.       restartPolicy: Always

    Kubernetes volume 支持非常多的插件，可以根据实际需要来选择：

    • emptyDir
    • hostPath
    • gcePersistentDisk
    • awsElasticBlockStore
    • nfs
    • iscsi
    • flocker
    • glusterfs
    • rbd
    • cephfs
    • gitRepo
    • secret
    • persistentVolumeClaim
    • downwardAPI
    • azureFileVolume
    • vsphereVolume
    1. $ kubectl expose deployment nginx-app --port=80 --target-port=80 --type=NodePort
    2. service "nginx-app" exposed
    3. $ kubectl describe service nginx-app
    4. Name:              nginx-app
    5. Namespace:             default
    6. Labels:            run=nginx-app
    7. Selector:              run=nginx-app
    8. Type:              ClusterIP
    9. IP:                10.0.0.66
    10. Port:              <unset>    80/TCP
    11. NodePort:              <unset>    30772/TCP
    12. Endpoints:             172.17.0.3:80
    13. Session Affinity:          None

    这样，在 cluster 内部就可以通过 http://10.0.0.66 和 来访问 nginx-app。而在 cluster 外面，则只能通过 http://node-ip:30772 来访问。