kubernetes入门实践

2022-08-27 23:11:18

k8s中文文档

  • k8s概念比较多，有什么概念的疑惑的推荐看k8s中文文档。

me的环境

  • 操作系统：centos7
  • docker：1.12.6

环境跟me的不一致？不要慌，基本大部分操作都是行的通的。

还慌？那就直接用网页在线版的kubernets吧

kubernets单机版安装部署

kubernetes部署算是有一定门槛的。为了不从入门到放弃，推荐一开始安装单机版作为入门熟悉kubectl指令、了解工作原理。

  • 安装流程，切换成root

    


    # 关闭centos自带的防火墙 
    


    $ sudo systemctl disable firewalld 
    

    $ sudo systemctl stop firewalld  
    


    # 安装etcd和kubernetes软件（会自动安装docker） 
    


    $ sudo yum install -y etcd kubernetes

  • 修改两处配置

    1. Docker配置文件/etc/sysconfig/docker, OPTIONS=’–selinux-enabled=false –insecure-registry gcr.io’

kubernetes入门实践

  1. Kubernetes apiservce配置文件/etc/kubernetes/apiserver,把–admission_control参数钟的ServiceAccount删除

kubernetes入门实践

启动所有服务



# systemctl start etcd 


# systemctl start docker 


# systemctl start kube-apiserver 


# systemctl start kube-controller-manager 


# systemctl start kube-scheduler 


# systemctl start kubelet 


# systemctl start kube-proxy

初入门小实例

  • 部署nginx服务

    

    $ kubectl run my-nginx --image=nginx --port=80 
    

    $ kubectl get pod  # 查看pod

发现pod状态无论多久都是处于pending。READY字段一直是0/1,服务部署失败的原因是”中国墙“的问题导致无法下载pod启动时需要的谷歌镜像，所以我们得间接的创建所需的镜像。

补充： Pending状态表示API Server已经创建Pod，但Pod内还有一个或者多个容器没有创建，或者正在下载镜像的过程。详细的参考Pod声明周期和重启策略

  • 创建gcr.io/google_containers/pause-amd64:3.0镜像

    

    $ docker pull googlecontainer/pause-amd64:3.0 
    

    $ docker tag googlecontainer/pause-amd64:3.0 gcr.io/google_containers/pause-amd64:3.0

    ​

kubernets指令

  • 实例流程


# 查看版本 


$ kubectl  version 


Client Version: version.Info{Major:"1", Minor:"5", GitVersion:"v1.5.2", GitCommit:"269f928217957e7126dc87e6adfa82242bfe5b1e", GitTreeState:"clean", BuildDate:"2017-07-03T15:31:10Z", GoVersion:"go1.7.4", Compiler:"gc", Platform:"linux/amd64"} 


Server Version: version.Info{Major:"1", Minor:"5", GitVersion:"v1.5.2", GitCommit:"269f928217957e7126dc87e6adfa82242bfe5b1e", GitTreeState:"clean", BuildDate:"2017-07-03T15:31:10Z", GoVersion:"go1.7.4", Compiler:"gc", Platform:"linux/amd64"} 



# 显示集群信息 


$ kubectl cluster-info 


Kubernetes master is running at http://localhost:8080 


To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'. 



# 查看集群中有几个Node 


$ kubectl get nodes 


NAME        STATUS    AGE 


127.0.0.1   Ready     18h 



# 运行一个镜像 


$ kubectl run my-nginx --image=nginx --replicas=2 --port=80 


deployment "my-nginx" created 



# 查看pod 


$ kubectl  get pods 


NAME                       READY     STATUS              RESTARTS   AGE 


my-nginx-379829228-cwlbb   0/1       ContainerCreating   0          20s 


my-nginx-379829228-czk6w   1/1       Running             0          20s 



# 查看服务详情信息 


$ kubectl  describe pod my-nginx-379829228-cwlbb 



# 查看已部署 


$ kubectl  get deployments 


NAME       DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE 


my-nginx   2         2         2            2           3m 



# 删除pod 


$ kubectl delete pod my-nginx-379829228-cwlbb 


pod "my-nginx-379829228-cwlbb" deleted 



# 再次查看pod，发现由于replicas机制，pod又生成一个新的 


$ kubectl  get pods 


NAME                       READY     STATUS              RESTARTS   AGE 


my-nginx-379829228-czk6w   1/1       Running             0          11m 


my-nginx-379829228-gjd7d   0/1       ContainerCreating   0          5s 



# 删除部署的my-nginx服务。彻底删除pod 


$ kubectl delete deployment my-nginx 


deployment "my-nginx" deleted

对比docker命令

k8s的学习路线基本都是从docker[容器]到k8s的，因此两个对比理解有助于记忆



# docker run 


$ docker run -d -e DOMAIN=cluster --name my-nginx -p 80:80 nginx 


$ kubectl run my-nginx --image=nginx --port=80 --env="DOMAIN=cluster" 



# docker ps  


$ docker ps  


$ kubectl get pods 



# docker exec 


$ docker exec [容器id] ls 


$ kubectl exec [pod_id] ls 



# docker exec 交互式 


$ docker exec -it [容器id] /bin/sh 


$ kubectl exec -it [pod_id] -- /bin/sh 



# docker info 


$ docker info  


$ kubectl cluster-info

重要名词

名词 翻译
Namespace 命名空间
Endpoint 服务端点
Controller Manager 管理控制中心
Replication 副本控制器

yaml文件管理服务

  • 用yaml文件来创建服务

    


    # vi nginx.yaml 
    



    piVersion: extensions/v1beta1 
    

    kind: Deployment 
    

    metadata: 
    

    name: my-nginx 
    

    spec: 
    

    replicas: 3 
    

    template: 
    

      metadata: 
    

        labels: 
    

          app: nginx 
    

      spec: 
    

        containers: 
    

        - name: nginx 
    

          image: nginx:1.7.9 
    

          ports: 
    

          - containerPort: 80

  • 启动管理服务

    


    # 根据yaml文件创建服务 
    


    $ kubectl create -f nginx.yaml  
    

    deployment "my-nginx" created 
    


    # 查看deployment 
    


    $ kubectl get deployments 
    

    NAME       DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE 
    

    my-nginx   3         3         3            3           6s 
    


    # 查看Pod 
    


    $ kubectl get pod 
    

    NAME                        READY     STATUS    RESTARTS   AGE 
    

    my-nginx-4087004473-dtrjp   1/1       Running   0          7s 
    

    my-nginx-4087004473-jz80p   1/1       Running   0          7s 
    

    my-nginx-4087004473-wh576   1/1       Running   0          7s 
    


    # 根据yaml文件删除服务 
    


    $ kubectl delete -f nginx.yaml  
    

    deployment "my-nginx" deleted 
    


    $ kubectl get pod 
    

    No resources found. 
    

    $ kubectl get deployment 
    

    No resources found.

    ​

    ​

Service

  • 到此，我们部署一个nginx服务

    

    $ kubectl run my-nginx --image=nginx --port=80 
    


    # 创建一个service 且将其暴露到集群外可供访问 
    


    $ kubectl expose deployment/my-nginx --type="NodePort" --port 80 
    

    service "my-nginx" exposed 
    


    # 此时service列表多个my-nginx服务 
    


    $ kubectl get services 
    

    NAME         CLUSTER-IP       EXTERNAL-IP   PORT(S)        AGE 
    

    kubernetes   10.254.0.1       <none>        443/TCP        7d 
    

    my-nginx     10.254.255.103   <nodes>       80:32589/TCP   7s

宿主主机内访问该服务

kubernetes入门实践

同网段的机器访问该服务

kubernetes入门实践

deployments



# 运行nginx镜像 


$ kubectl run my-nginx --image=nginx --port=80 


# 交互式 shell 的方式运行 pod 


$ kubectl run -i --tty my-nginx --image=nginx --port=80 -- sh 


# 链接到运行中的容器 


$ kubectl attach my-nginx-532658988-10kxd -i 



# 查看deployment 


$ kubectl get deployments 


NAME       DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE 


my-nginx   1         1         1            1           25m 


# 扩展10个副本 


$ kubectl scale deployment my-nginx --replicas=10 


deployment "my-nginx" scaled 


$ kubectl scale  deployment/my-nginx --replicas=10 # 作用效果等同上一条命令  


deployment "my-nginx" scaled 


# 再次显示deployment 


$ kubectl get deployments 


NAME       DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE 


my-nginx   10        10        10           1           26m 


$ kubectl get pods 


NAME                       READY     STATUS    RESTARTS   AGE 


my-nginx-379829228-38hkg   1/1       Running   0          5m 


my-nginx-379829228-7j15l   1/1       Running   0          31m 


my-nginx-379829228-c8mt3   1/1       Running   0          5m 


my-nginx-379829228-f6mm8   1/1       Running   0          5m 


my-nginx-379829228-q1rj0   1/1       Running   0          5m 


my-nginx-379829228-qg7lf   1/1       Running   0          5m 


my-nginx-379829228-rjfbq   1/1       Running   0          5m 


my-nginx-379829228-v581r   1/1       Running   0          5m 


my-nginx-379829228-wh49w   1/1       Running   0          5m 


my-nginx-379829228-wpn98   1/1       Running   0          5m 



# 缩扩到1个副本 


$ kubectl scale  deployment/my-nginx --replicas=1 


deployment "my-nginx" scaled 


$ kubectl scale deployment my-nginx --replicas=1   # 作用效果等同上一条命令

deployment的更新回滚

kubernetes入门实践



$ kubectl create -f nginx.yaml 


$ kubectl get pod 


NAME                        READY     STATUS    RESTARTS   AGE 


my-nginx-4087004473-4xj74   1/1       Running   0          3m 


my-nginx-4087004473-jkptq   1/1       Running   0          3m 


my-nginx-4087004473-m55s1   1/1       Running   0          3m 


$ kubectl get deployment 


NAME       DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE 


my-nginx   3         3         3            3           4m 


# 更新应用的镜像从1.7.9版本——>1.9.1 


$ kubectl set image deployment/my-nginx nginx=nginx:1.9.1 


deployment "my-nginx" image updated 


# 确认是否更新成功 


$ kubectl rollout status deployment/my-nginx 


deployment "my-nginx" successfully rolled out 


# 回滚到上一代版本 


$ kubectl rollout undo deployment/my-nginx 


deployment "my-nginx" rolled back

ConfigMap-容器应用的配置管理

应用部署的一个最佳实践是将应用所需配置信息和程序进行分离，一则程序可以更好的复用，二则能灵活的更改配置从而实现其他功能。

使用configMap替代环境变量

以yaml文件方式创建ConfigMap



# vi special-config.yaml 



apiVersion: v1 


kind: ConfigMap 


metadata: 


  name: special-config 


  namespace: default 


data: 


  special.how: very 


  special.type: charm 





# vi env-config.yaml 



apiVersion: v1 


kind: ConfigMap 


metadata: 


  name: env-config 


  namespace: default 


data: 


  log_level: INFO

可以在Pod中这样使用ConfigMap



# vi configMap.yaml 



apiVersion: v1 


kind: Pod 


metadata: 


  name: dapi-test-pod 


spec: 


  containers: 


    - name: test-container 


      image: nginx 


      command: [ "/bin/sh", "-c", "env" ] 


      env: 


        - name: SPECIAL_LEVEL_KEY   #定义环境变量名称 


          valueFrom:       #key"special.how"对应的值 


            configMapKeyRef: 


              name: special-config #环境变量的值 


              key: special.how 


        - name: SPECIAL_TYPE_KEY 


          valueFrom: 


            configMapKeyRef: 


              name: special-config 


              key: special.type 


  restartPolicy: Never

启动等一系列操作



$ kubectl create -f special-config.yaml 


configmap "special-config" created 


$ kubectl create -f env-config.yaml 


configmap "env-config" created 


# 查看ConfigMap 


$ kubectl get configmaps 


NAME             DATA      AGE 


env-config       1         38m 


special-config   2         39m 


# 让我们看一下创建的ConfigMap 


$  kubectl describe configmap env-config 


Name:       env-config 


Namespace:  default 


Labels:     <none> 


Annotations:    <none> 



Data 


==== 


log_level:  4 bytes 



# 查看ConfigMap键的值 


$ kubectl get configmaps env-config -o yaml 


apiVersion: v1 


data: 


  log_level: INFO 


kind: ConfigMap 


metadata: 


  creationTimestamp: 2017-11-30T07:29:49Z 


  name: env-config 


  namespace: default 


  resourceVersion: "285268" 


  selfLink: /api/v1/namespaces/default/configmaps/env-config 


  uid: 3f473adf-d5a0-11e7-9830-0800275ae9e7

​



$ kubectl create -f configMap.yaml 


pod "dapi-test-pod" created 


# 查看pod，状态ContainerCreating 


$ kubectl get pod 


NAME            READY     STATUS              RESTARTS   AGE 


dapi-test-pod   0/1       ContainerCreating   0          3s 


# 隔一段时间再查看pod,发现并没有返回什么 


$  kubectl get pod 


# 显示所有的权限查看pod 


$ kubectl get pod --show-all 


NAME            READY     STATUS      RESTARTS   AGE 


dapi-test-pod   0/1       Completed   0          1m 


# 查看详情 


$ kubectl describe pod dapi-test-pod 


Name:       dapi-test-pod 


Namespace:  default 


Node:       127.0.0.1/127.0.0.1 


Start Time: Thu, 30 Nov 2017 15:32:00 +0800 


Labels:     <none> 


Status:     Succeeded 


IP:      


Controllers:    <none> 


Containers: 


  test-container: 


    Container ID:   docker://1ba533f43ee60c02e03dafb7bcb8495fc12264aaab229872df0b289a3c1b9976 


    Image:      nginx 


    Image ID:       docker-pullable://docker.io/nginx@sha256:b81f317384d7388708a498555c28a7cce778a8f291d90021208b3eba3fe74887 


    Port:        


    Command: 


      /bin/sh 


      -c 


      env 


    State:      Terminated 


      Reason:       Completed 


      Exit Code:    0 


      Started:      Thu, 30 Nov 2017 15:32:25 +0800 


      Finished:     Thu, 30 Nov 2017 15:32:25 +0800 


    Ready:      False 


    Restart Count:  0 


    Volume Mounts:  <none> 


    Environment Variables: 


      SPECIAL_LEVEL_KEY:    <set to the key 'special.how' of config map 'special-config'> 


      SPECIAL_TYPE_KEY:     <set to the key 'special.type' of config map 'special-config'> 


Conditions: 


  Type      Status 


  Initialized   True  


  Ready     False  


  PodScheduled  True  


No volumes. 


QoS Class:  BestEffort 


Tolerations:    <none> 


Events: 


  FirstSeen LastSeen    Count   From            SubObjectPath           Type        Reason          Message 


  --------- --------    -----   ----            -------------           --------    ------          ------- 


  3m        3m      1   {default-scheduler }                    Normal      Scheduled       Successfully assigned dapi-test-pod to 127.0.0.1 


  3m        3m      1   {kubelet 127.0.0.1} spec.containers{test-container} Normal      Pulling         pulling image "nginx" 


  3m        2m      2   {kubelet 127.0.0.1}                 Warning     MissingClusterDNS   kubelet does not have ClusterDNS IP configured and cannot create Pod using "ClusterFirst" policy. Falling back to DNSDefault policy. 


  2m        2m      1   {kubelet 127.0.0.1} spec.containers{test-container} Normal      Pulled          Successfully pulled image "nginx" 


  2m        2m      1   {kubelet 127.0.0.1} spec.containers{test-container} Normal      Created         Created container with docker id 1ba533f43ee6; Security:[seccomp=unconfined] 


  2m        2m      1   {kubelet 127.0.0.1} spec.containers{test-container} Normal      Started         Started container with docker id 1ba533f43ee6 


# 可知container started 成功，进一步查看日志 


$ docker logs 1ba 


KUBERNETES_SERVICE_PORT=443 


KUBERNETES_PORT=tcp://10.254.0.1:443 


MY_SERVICE_PORT_80_TCP=tcp://10.254.110.249:80 


MY_SERVICE_PORT_443_TCP_ADDR=10.254.110.249 


HOSTNAME=dapi-test-pod 


MY_SERVICE_PORT_443_TCP_PORT=443 


HOME=/root 


MY_SERVICE_PORT_443_TCP_PROTO=tcp 


MY_SERVICE_SERVICE_PORT_HTTP=80 


SPECIAL_TYPE_KEY=charm 


MY_SERVICE_SERVICE_PORT_HTTPS=443 


MY_SERVICE_PORT_443_TCP=tcp://10.254.110.249:443 


MY_SERVICE_SERVICE_HOST=10.254.110.249 


KUBERNETES_PORT_443_TCP_ADDR=10.254.0.1 


NGINX_VERSION=1.13.7-1~stretch 


PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin 


KUBERNETES_PORT_443_TCP_PORT=443 


NJS_VERSION=1.13.7.0.1.15-1~stretch 


KUBERNETES_PORT_443_TCP_PROTO=tcp 


MY_SERVICE_SERVICE_PORT=80 


MY_SERVICE_PORT=tcp://10.254.110.249:80 


SPECIAL_LEVEL_KEY=very 


MY_SERVICE_PORT_80_TCP_ADDR=10.254.110.249 


KUBERNETES_PORT_443_TCP=tcp://10.254.0.1:443 


KUBERNETES_SERVICE_PORT_HTTPS=443 


KUBERNETES_SERVICE_HOST=10.254.0.1 


MY_SERVICE_PORT_80_TCP_PORT=80 


PWD=/ 


MY_SERVICE_PORT_80_TCP_PROTO=tcp

​

ConfigMap的限制条件

  • ConfigMap必须在Pod之前创建才能被使用。
  • ConfigMap可以定义其属于哪个Namspece，只有在同一个Namespace中的pod才能引用。

删除Pod

  • 有时候deployment、rs、rc、services都为0，但是Pod确存在着。则重启kubelet服务即可。


$ systemctl restart kubelet

补充



# 列出当前节点名 


kubectl get node 


NAME        STATUS    AGE 


127.0.0.1   Ready     6d 


# 已知当前节点名为127.0.0.1,用如下命令即可获得该节点上所有运行节点 


$ curl localhost:8080/api/v1/proxy/nodes/127.0.0.1/pods 


{"kind":"PodList","apiVersion":"v1","metadata":{},"items":null}

报错



$ sudo kubectl create -f file.yaml 


YAML error: found character that cannot start any token  


# or 


error:yaml: line 15: found a tab character that violate indentation 



#file.yaml不可用tab键来空格 



$ sudo  kubectl  create -f mysql-rc.yaml  


error: error validating "mysql-rc.yaml": error validating data: [found invalid field app for v1.ObjectMeta, found invalid field value for v1.Container]; if you choose to ignore these errors, turn validation off with --validate=false 






--------------------- 



# kubectl get pod --all-namespaces 


NAMESPACE     NAME                                    READY     STATUS              RESTARTS   AGE 


default       my-nginx-379829228-b796w                1/1       Running             0          12m 


kube-system   kubernetes-dashboard-2397086622-46tvx   0/1       ContainerCreating   0          8s 



[root@node01 ~]# kubectl logs -f kubernetes-dashboard-2397086622-46tvx  --namespace=kube-system   


Using HTTP port: 9090 


Using apiserver-host location: http://127.0.0.1:8080 


Creating API server client for http://127.0.0.1:8080 


Error while initializing connection to Kubernetes apiserver. This most likely means that the cluster is misconfigured (e.g., it has invalid apiserver certificates or service accounts configuration) or the --apiserver-host param points to a server that does not exist. Reason: Get http://127.0.0.1:8080/version: dial tcp 127.0.0.1:8080: getsockopt: connection refused 


Refer to the troubleshooting guide for more information: https://github.com/kubernetes/dashboard/blob/master/docs/user-guide/troubleshooting.md
我们最好不要越过RC而直接创建Pod,因为Replication Controller会通过RC管理Pod副本。实现自动创建、补足、替换、删除Pod副本，大大提高系统的容灾能力
  • 重新调度(Rescheduling)
  • 弹性伸缩(Scaling)
  • 滚动更新(Rolling Updates)
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