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Kubernetes集群客户端工具kubectl
我们已经能够部署Kubernetes了，那么我们如何使用Kubernetes集群运行企业的应用程序呢？那么，我们就需要使用命令行工具kubectl。
kubectl就是控制Kubernetes的驾驶舱，它允许你执行所有可能的Kubernetes操作，从技术角度来看，Kubectl就是Kubernetes API的一个客户端而已。
Kubernetes API 是一个 HTTP REST API 服务，该 API 服务才是 Kubernetes 的真正用到的用户接口，所以 Kubernetes 通过该 API 进行实际的控制。这也就意味着每个 Kubernetes 的操作都会通过 API 端点暴露出去，当然也就可以通过对这些 API 端口进行 HTTP 请求来执行相应的操作。所以，kubectl 最主要的工作就是执行 Kubernetes API 的 HTTP 请求。
学习目标：
了解kubectl 命令帮助方法
了解kubectl子命令使用分类
课程内容：
1、kubectl帮助方法：
我们预先是在所有节点上安装了kubectl工具。
# 检查kubectl是否安装：
[root@master1 ~]# rpm -qa |grep kubectl
kubectl-1.21.10-0.x86_64
[root@master1 ~]## 获取kubectl帮助方法：
[root@master1 ~]# kubectl --help
kubectl controls the Kubernetes cluster manager.Find more information at:
https://kubernetes.io/docs/reference/kubectl/overview/Basic Commands (Beginner):create Create a resource from a file or from stdin.expose Take a replication controller, service, deployment or pod and
expose it as a new Kubernetes Servicerun Run a particular image on the clusterset Set specific features on objectsBasic Commands (Intermediate):explain Documentation of resourcesget Display one or many resourcesedit Edit a resource on the serverdelete Delete resources by filenames, stdin, resources and names, or by
resources and label selectorDeploy Commands:rollout Manage the rollout of a resourcescale Set a new size for a Deployment, ReplicaSet or Replication
Controllerautoscale Auto-scale a Deployment, ReplicaSet, StatefulSet, or
ReplicationControllerCluster Management Commands:certificate Modify certificate resources.cluster-info Display cluster infotop Display Resource (CPU/Memory) usage.cordon Mark node as unschedulableuncordon Mark node as schedulabledrain Drain node in preparation for maintenancetaint Update the taints on one or more nodesTroubleshooting and Debugging Commands:describe Show details of a specific resource or group of resourceslogs Print the logs for a container in a podattach Attach to a running containerexec Execute a command in a containerport-forward Forward one or more local ports to a podproxy Run a proxy to the Kubernetes API servercp Copy files and directories to and from containers.auth Inspect authorizationdebug Create debugging sessions for troubleshooting workloads and
nodesAdvanced Commands:diff Diff live version against would-be applied versionapply Apply a configuration to a resource by filename or stdinpatch Update field(s) of a resourcereplace Replace a resource by filename or stdinwait Experimental: Wait for a specific condition on one or many
resources.kustomize Build a kustomization target from a directory or URL.Settings Commands:label Update the labels on a resourceannotate Update the annotations on a resourcecompletion Output shell completion code for the specified shell (bash or
zsh)Other Commands:api-resources Print the supported API resources on the serverapi-versions Print the supported API versions on the server, in the form of
"group/version"config Modify kubeconfig filesplugin Provides utilities for interacting with plugins.version Print the client and server version informationUsage:kubectl [flags] [options]Use "kubectl <command> --help" for more information about a given command.
Use "kubectl options" for a list of global command-line options (applies to all
commands).kubectl子命令使用分类：
列出所有pod并显示详细信息
[root@master1 ~]# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-65c4bffcb6-gd9z6 1/1 Running 0 8h 10.244.1.4 worker1 <none> <none>
查看所有deployment对象。
[root@master1 ~]# kubectl get deployment nginx
NAME READY UP-TO-DATE AVAILABLE AGE
nginx 1/1 1 1 9h
查看所有service对象：
[root@master1 ~]# kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 10h
nginx NodePort 10.101.138.1 <none> 80:30831/TCP 9h
[root@master1 ~]#
[root@master1 ~]#
[root@master1 ~]# kubectl get service
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 10h
nginx NodePort 10.101.138.1 <none> 80:30831/TCP 9h
查看不同namespace下的Pod对象：
[root@master1 ~]# kubectl get pods -n default
NAME READY STATUS RESTARTS AGE
nginx-65c4bffcb6-gd9z6 1/1 Running 0 9h[root@master1 ~]# kubectl get pods --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE
default nginx-65c4bffcb6-gd9z6 1/1 Running 0 9h
kube-flannel kube-flannel-ds-dvjnd 1/1 Running 0 9h
kube-flannel kube-flannel-ds-gxl4h 1/1 Running 0 9h
kube-flannel kube-flannel-ds-jvdzc 1/1 Running 0 9h
kube-system calico-kube-controllers-594649bd75-xjbgr 1/1 Running 0 9h
kube-system calico-node-6lz45 1/1 Running 0 9h
kube-system calico-node-fdprn 1/1 Running 0 9h
kube-system calico-node-szs6x 1/1 Running 0 9h
kube-system coredns-558bd4d5db-fmrpg 1/1 Running 0 10h
kube-system coredns-558bd4d5db-fnxdn 1/1 Running 0 10h
kube-system etcd-master1 1/1 Running 1 10h
kube-system kube-apiserver-master1 1/1 Running 1 10h
kube-system kube-controller-manager-master1 1/1 Running 1 10h
kube-system kube-proxy-rz26h 1/1 Running 0 9h
kube-system kube-proxy-spf9t 1/1 Running 1 9h
kube-system kube-proxy-x4fq5 1/1 Running 0 10h
kube-system kube-scheduler-master1 1/1 Running 1 10h
查看资源描述：
[root@master1 ~]# kubectl describe pods
Name: nginx-65c4bffcb6-gd9z6
Namespace: default
Priority: 0
Node: worker1/192.168.17.147
Start Time: Sat, 06 Apr 2024 19:04:43 +0800
Labels: app=nginxpod-template-hash=65c4bffcb6
Annotations: <none>
Status: Running
IP: 10.244.1.4
IPs:IP: 10.244.1.4
Controlled By: ReplicaSet/nginx-65c4bffcb6
Containers:nginx:Container ID: docker://b0860e41573587a5c065c9aa18c398475b1b31f9f56d7d3c2e04171f80f1e1c1Image: nginx:1.14-alpineImage ID: docker-pullable://nginx@sha256:485b610fefec7ff6c463ced9623314a04ed67e3945b9c08d7e53a47f6d108dc7Port: <none>Host Port: <none>State: RunningStarted: Sat, 06 Apr 2024 19:05:04 +0800Ready: TrueRestart Count: 0Environment: <none>Mounts:/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-mjhtz (ro)
Conditions:Type StatusInitialized TrueReady TrueContainersReady TruePodScheduled True
Volumes:kube-api-access-mjhtz:Type: Projected (a volume that contains injected data from multiple sources)TokenExpirationSeconds: 3607ConfigMapName: kube-root-ca.crtConfigMapOptional: <nil>DownwardAPI: true
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300snode.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events: <none>
所有的命令都要熟练使用。
使用kubectl命令必要环境：
在worker节点如何使用kubectl命令管理K8s集群？
准备集群管理配置文件：
mkdir .kube
scp master1:/root/.kube/config .kube/使用命令验证：
[root@worker1 ~]# kubectl get nodes
NAME STATUS ROLES AGE VERSION
master1 Ready control-plane,master 10h v1.21.10
worker1 Ready <none> 10h v1.21.10
worker2 Ready <none> 10h v1.21.10
其中这个config的配置文件：
这是一个连接Kubernetes API （IP地址+端口），就能管理到集群。