kubectl是一个用于操作kubernetes集群的命令行接口,通过利用kubectl的各种命令可以实现各种功能,是在使用kubernetes中非常常用的工具。这里我们会通过一些简单的实例来展现其中一些高频命令的使用方法。
更为重要的是这些命令使用的场景以及能够解决什么样的问题。上篇文章我们介绍了创建和删除相关的几条命令，这篇文章我们来看一下出现问题时最常用的另外九条命令。

常用命令

kubectl故障排查相关，本文将会简单介绍一下如下命令

事前准备

kubectl version

version命令用于确认客户端和服务器侧的版本信息，不同的版本的情况变化可能很大，所以故障排除时首先也需要确认的是现场环境的版本信息。
从下面可以清楚地看到，本文验证时所使用的版本为1.5.2

[root@ku8-1 tmp]# kubectl versionClient Version: version.Info{Major:"1", Minor:"5", GitVersion:"v1.5.2", GitCommit:"08e099554f3c31f6e6f07b448ab3ed78d0520507", GitTreeState:"clean", BuildDate:"2017-01-12T04:57:25Z", GoVersion:"go1.7.4", Compiler:"gc", Platform:"linux/amd64"}Server Version: version.Info{Major:"1", Minor:"5", GitVersion:"v1.5.2", GitCommit:"08e099554f3c31f6e6f07b448ab3ed78d0520507", GitTreeState:"clean", BuildDate:"2017-01-12T04:52:34Z", GoVersion:"go1.7.4", Compiler:"gc", Platform:"linux/amd64"}[root@ku8-1 tmp]#

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集群构成

一主三从的Kubernetes集群

[root@ku8-1 tmp]# kubectl get nodesNAME STATUS AGE192.168.32.132 Ready 12m192.168.32.133 Ready 11m192.168.32.134 Ready 11m[root@ku8-1 tmp]# 

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kubectl api-versions

使用api-versions命令可以列出当前版本的kubernetes的服务器端所支持的api版本信息。

[root@ku8-1 tmp]# kubectl api-versionsapps/v1beta1authentication.k8s.io/v1beta1authorization.k8s.io/v1beta1autoscaling/v1batch/v1certificates.k8s.io/v1alpha1extensions/v1beta1policy/v1beta1rbac.authorization.k8s.io/v1alpha1storage.k8s.io/v1beta1v1[root@ku8-1 tmp]#

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kubectl explain

使用kubectl explain可以和kubectl help一样进行辅助的功能确认，使用它可以了解各个部分的说明和组成部分。比如如下可以看到对rc的说明，在故障排除时作用并不具有太大作用，到是可以多读读加深一下对各个部分的理解。

[root@ku8-1 ~]# kubectl explain rcDESCRIPTION:ReplicationController represents the configuration of a replication controller.FIELDS: apiVersion <string> APIVersion defines the versioned schema of this representation of an object. Servers should convert recognized schemas to the latest internal value, and may reject unrecognized values. More info: http://releases.k8s.io/HEAD/docs/devel/api-conventions.md#resources kind <string> Kind is a string value representing the REST resource this object represents. Servers may infer this from the endpoint the client submits requests to. Cannot be updated. In CamelCase. More info: http://releases.k8s.io/HEAD/docs/devel/api-conventions.md#types-kinds metadata <Object> If the Labels of a ReplicationController are empty, they are defaulted to be the same as the Pod(s) that the replication controller manages. Standard object‘s metadata. More info: http://releases.k8s.io/HEAD/docs/devel/api-conventions.md#metadata spec <Object> Spec defines the specification of the desired behavior of the replication controller. More info: http://releases.k8s.io/HEAD/docs/devel/api-conventions.md#spec-and-status status <Object> Status is the most recently observed status of the replication controller. This data may be out of date by some window of time. Populated by the system. Read-only. More info: http://releases.k8s.io/HEAD/docs/devel/api-conventions.md#spec-and-status[root@ku8-1 ~]# 

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explain命令能够确认的信息类别

其所能支持的类别如下：

事前准备

剩下的一些命令需要事前作一些准备，我们还是用上篇文章所用的yaml文件创建mysql和sonarqube的Deployment和pod。

yaml文件准备

[root@ku8-1 tmp]# ls yamlsmysql.yaml sonar.yaml[root@ku8-1 tmp]# cat yamls/mysql.yaml ---kind: DeploymentapiVersion: extensions/v1beta1metadata: name: mysqlspec: replicas: 1 template: metadata: labels: name: mysql spec: containers: - name: mysql image: 192.168.32.131:5000/mysql:5.7.16 ports: - containerPort: 3306 protocol: TCP env: - name: MYSQL_ROOT_PASSWORD value: "hello123"[root@ku8-1 tmp]# cat yamls/sonar.yaml ---kind: DeploymentapiVersion: extensions/v1beta1metadata: name: sonarqubespec: replicas: 1 template: metadata: labels: name: sonarqube spec: containers: - name: sonarqube image: 192.168.32.131:5000/sonarqube:5.6.5 ports: - containerPort: 9000 protocol: TCP[root@ku8-1 tmp]# 

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启动

[root@ku8-1 tmp]# kubectl create -f yamls/deployment "mysql" createddeployment "sonarqube" created[root@ku8-1 tmp]# 

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kubectl get

使用get命令确认所创建出来的pod和deployment的信息

确认pod

可以看到创建出来的pod的所有信息,也可以使用Kubectl get po进行确认

[root@ku8-1 tmp]# kubectl get podsNAME READY STATUS RESTARTS AGEmysql-478535978-1dnm2 1/1 Running 0 34ssonarqube-3574384362-m7mdq 1/1 Running 0 34s[root@ku8-1 tmp]# 

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确认deployment

可以看到创建出来的deployment的所有信息

[root@ku8-1 tmp]# kubectl get deploymentsNAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGEmysql 1 1 1 1 41ssonarqube 1 1 1 1 41s[root@ku8-1 tmp]#

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如果希望得到更加详细一点的信息，可以加上-o wide参数,比如对pods可以看到此pod在哪个node上运行，此pod的集群IP是多少也被一并显示了

[root@ku8-1 tmp]# kubectl get pods -o wideNAME READY STATUS RESTARTS AGE IP NODEmysql-478535978-1dnm2 1/1 Running 0 2m 172.200.44.2 192.168.32.133sonarqube-3574384362-m7mdq 1/1 Running 0 2m 172.200.59.2 192.168.32.134[root@ku8-1 tmp]#

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确认node信息

显示node的信息

[root@ku8-1 tmp]# kubectl get nodes -o wideNAME STATUS AGE EXTERNAL-IP192.168.32.132 Ready 6h <none>192.168.32.133 Ready 6h <none>192.168.32.134 Ready 6h <none>[root@ku8-1 tmp]#

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确认namespace信息

列出所有的namespace

[root@ku8-1 tmp]# kubectl get namespacesNAME STATUS AGEdefault Active 6hkube-system Active 6h[root@ku8-1 tmp]# 

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get命令能够确认的信息类别

使用node/pod/event/namespaces等结合起来，能够获取集群基本信息和状况, 其所能支持的类别如下：

kubectl describe

确认node详细信息

一般使用get命令取得node信息，然后使用describe确认详细信息。

[root@ku8-1 tmp]# kubectl get nodesNAME STATUS AGE192.168.32.132 Ready 6h192.168.32.133 Ready 6h192.168.32.134 Ready 6h[root@ku8-1 tmp]# kubectl describe node 192.168.32.132Name: 192.168.32.132Role: Labels: beta.kubernetes.io/arch=amd64 beta.kubernetes.io/os=linux kubernetes.io/hostname=192.168.32.132Taints: <none>CreationTimestamp: Wed, 28 Jun 2017 23:06:22 -0400Phase: Conditions: Type Status LastHeartbeatTime LastTransitionTime Reason Message ---- ------ ----------------- ------------------ ------ ------- OutOfDisk False Thu, 29 Jun 2017 05:52:07 -0400 Wed, 28 Jun 2017 23:06:22 -0400 KubeletHasSufficientDisk kubelet has sufficient disk space available MemoryPressure False Thu, 29 Jun 2017 05:52:07 -0400 Wed, 28 Jun 2017 23:06:22 -0400 KubeletHasSufficientMemory kubelet has sufficient memory available DiskPressure False Thu, 29 Jun 2017 05:52:07 -0400 Wed, 28 Jun 2017 23:06:22 -0400 KubeletHasNoDiskPressure kubelet has no disk pressure Ready True Thu, 29 Jun 2017 05:52:07 -0400 Wed, 28 Jun 2017 23:06:34 -0400 KubeletReady kubelet is posting ready statusAddresses: 192.168.32.132,192.168.32.132,192.168.32.132Capacity: alpha.kubernetes.io/nvidia-gpu: 0 cpu: 1 memory: 2032128Ki pods: 110Allocatable: alpha.kubernetes.io/nvidia-gpu: 0 cpu: 1 memory: 2032128Ki pods: 110System Info: Machine ID: 22718f24279240be9fe0c469187f901a System UUID: 9F584D56-F5B3-FAB8-3985-938D67451312 Boot ID: fe3b2606-37ee-4b07-8de2-438fe29bf765 Kernel Version: 3.10.0-514.el7.x86_64 OS Image: CentOS Linux 7 (Core) Operating System: linux Architecture: amd64 Container Runtime Version: docker://1.13.1 Kubelet Version: v1.5.2 Kube-Proxy Version: v1.5.2ExternalID: 192.168.32.132Non-terminated Pods: (0 in total) Namespace Name CPU Requests CPU Limits Memory Requests Memory Limits --------- ---- ------------ ---------- --------------- -------------Allocated resources: (Total limits may be over 100 percent, i.e., overcommitted. CPU Requests CPU Limits Memory Requests Memory Limits ------------ ---------- --------------- ------------- 0 (0%) 0 (0%) 0 (0%) 0 (0%)No events.[root@ku8-1 tmp]#

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确认pod

确认某一pod详细信息

[root@ku8-1 tmp]# kubectl describe pod mysql-478535978-1dnm2Name: mysql-478535978-1dnm2Namespace: defaultNode: 192.168.32.133/192.168.32.133Start Time: Thu, 29 Jun 2017 05:04:21 -0400Labels: name=mysql pod-template-hash=478535978Status: RunningIP: 172.200.44.2Controllers: ReplicaSet/mysql-478535978Containers: mysql: Container ID: docker://47ef1495e86f4b69414789e81081fa55b837dafe9e47944894e7cb3733700410 Image: 192.168.32.131:5000/mysql:5.7.16 Image ID: docker-pullable://192.168.32.131:5000/mysql@sha256:410b279f6827492da7a355135e6e9125849f62eeca76429974a534f021852b58 Port: 3306/TCP State: Running Started: Thu, 29 Jun 2017 05:04:22 -0400 Ready: True Restart Count: 0 Volume Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-dzs1w (ro) Environment Variables: MYSQL_ROOT_PASSWORD: hello123Conditions: Type Status Initialized True Ready True PodScheduled True Volumes: default-token-dzs1w: Type: Secret (a volume populated by a Secret) SecretName: default-token-dzs1wQoS Class: BestEffortTolerations: <none>No events.[root@ku8-1 tmp]# 

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确认deployment详细信息

确认某一deployment的详细信息

[root@ku8-1 tmp]# kubectl get deploymentNAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGEmysql 1 1 1 1 1hsonarqube 1 1 1 1 1h[root@ku8-1 tmp]# kubectl describe deployment mysqlName: mysqlNamespace: defaultCreationTimestamp: Thu, 29 Jun 2017 05:04:21 -0400Labels: name=mysqlSelector: name=mysqlReplicas: 1 updated | 1 total | 1 available | 0 unavailableStrategyType: RollingUpdateMinReadySeconds: 0RollingUpdateStrategy: 1 max unavailable, 1 max surgeConditions: Type Status Reason ---- ------ ------ Available True MinimumReplicasAvailableOldReplicaSets: <none>NewReplicaSet: mysql-478535978 (1/1 replicas created)No events.[root@ku8-1 tmp]# 

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describe命令能够确认的信息

describe命令所能支持的类别如下：

kubectl logs

类似于docker logs，使用kubectl logs能够取出pod中镜像的log，也是故障排除时候的重要信息

[root@ku8-1 tmp]# kubectl get podsNAME READY STATUS RESTARTS AGEmysql-478535978-1dnm2 1/1 Running 0 1hsonarqube-3574384362-m7mdq 1/1 Running 0 1h[root@ku8-1 tmp]# kubectl logs mysql-478535978-1dnm2Initializing database...2017-06-29T09:04:37.081939Z 0 [Note] Event Scheduler: Loaded 0 events2017-06-29T09:04:37.082097Z 0 [Note] mysqld: ready for connections.Version: ‘5.7.16‘ socket: ‘/var/run/mysqld/mysqld.sock‘ port: 3306 MySQL Community Server (GPL)[root@ku8-1 tmp]# 

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kubectl exec

exec命令用于到容器中执行一条命令，比如下述命令用于到mysql的镜像中执行hostname命令

[root@ku8-1 tmp]# kubectl get podsNAME READY STATUS RESTARTS AGEmysql-478535978-1dnm2 1/1 Running 0 1hsonarqube-3574384362-m7mdq 1/1 Running 0 1h[root@ku8-1 tmp]# kubectl exec mysql-478535978-1dnm2 hostnamemysql-478535978-1dnm2[root@ku8-1 tmp]# 

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更为常用的方式则是登陆到pod中，在有条件的时候，进行故障发生时的现场确认，这种方式是最为直接有效和快速，但是对权限要求也较多。

[root@ku8-1 tmp]# kubectl exec -it mysql-478535978-1dnm2 sh# hostnamemysql-478535978-1dnm2# 

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kubectl cp

用于pod和外部的文件交换，比如如下示例了如何在进行内外文件交换。

在pod中创建一个文件message.log

[root@ku8-1 tmp]# kubectl exec -it mysql-478535978-1dnm2 sh# pwd/# cd /tmp# echo "this is a message from `hostname`" >message.log# cat message.logthis is a message from mysql-478535978-1dnm2# exit[root@ku8-1 tmp]#

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拷贝出来并确认

[root@ku8-1 tmp]# kubectl cp mysql-478535978-1dnm2:/tmp/message.log message.logtar: Removing leading `/‘ from member names[root@ku8-1 tmp]# cat message.logthis is a message from mysql-478535978-1dnm2[root@ku8-1 tmp]#

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更改message.log并拷贝回pod

[root@ku8-1 tmp]# echo "information added in `hostname`" >>message.log [root@ku8-1 tmp]# cat message.log this is a message from mysql-478535978-1dnm2information added in ku8-1[root@ku8-1 tmp]# kubectl cp message.log mysql-478535978-1dnm2:/tmp/message.log[root@ku8-1 tmp]# 

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确认更改后的信息

[root@ku8-1 tmp]# kubectl exec mysql-478535978-1dnm2 cat /tmp/message.logthis is a message from mysql-478535978-1dnm2information added in ku8-1[root@ku8-1 tmp]#

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kubectl attach

类似于docker attach的功能，用于取得实时的类似于kubectl logs的信息

[root@ku8-1 tmp]# kubectl get podsNAME READY STATUS RESTARTS AGEmysql-478535978-1dnm2 1/1 Running 0 1hsonarqube-3574384362-m7mdq 1/1 Running 0 1h[root@ku8-1 tmp]# kubectl attach sonarqube-3574384362-m7mdqIf you don‘t see a command prompt, try pressing enter. 

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kubectl cluster-info

使用cluster-info和cluster-info dump也能取出一些信息，尤其是你需要看整体的全部信息的时候一条命令一条命令的执行不如kubectl cluster-info dump来的快一些

[root@ku8-1 tmp]# kubectl cluster-infoKubernetes master is running at http://localhost:8080To further debug and diagnose cluster problems, use ‘kubectl cluster-info dump‘.[root@ku8-1 tmp]# 

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总结

这篇文章中介绍了九个kubectl的常用命令，利用它们在故障确认和排查中非常有效。

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