Kubernetes学习笔记8

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。