一.系统环境

服务器版本	docker软件版本	CPU架构
CentOS Linux release 7.4.1708 (Core)	Docker version 20.10.12	x86_64

kubectl是Kubernetes提供的命令行工具，kubectl 使用 Kubernetes API 与 Kubernetes 集群的控制面进行通信。

针对配置信息，kubectl 在 $HOME/.kube 目录中查找一个名为 config 的配置文件来连接Kubernetes 集群。你可以通过设置 KUBECONFIG 环境变量或设置 --kubeconfig 参数来指定其它 kubeconfig 文件。

使用kubectl命令行工具的前提是已经有一套可以正常运行的Kubernetes集群，关于Kubernetes(k8s)集群的安装部署，可以查看博客《Centos7 安装部署Kubernetes(k8s)集群》https://www.cnblogs.com/renshengdezheli/p/16686769.html

三.kubectl

3.1 kubectl语法

kubectl的语法为：kubectl [command] [TYPE] [NAME] [flags]，其中 command、TYPE、NAME 和 flags 分别是：

command：指定要对一个或多个资源执行的操作，例如 create、get、describe、delete。
TYPE：指定资源类型。资源类型不区分大小写，可以指定单数、复数或缩写形式。例如，以下命令输出相同的结果：
```
kubectl get pod pod1
kubectl get pods pod1
kubectl get po pod1
```
NAME：指定资源的名称。名称区分大小写。如果省略名称，则显示所有资源的详细信息。例如：kubectl get pods。
flags：指定可选的参数。例如，可以使用 -s 或 --server 参数指定 Kubernetes API 服务器的地址和端口。

要对所有类型相同的资源进行分组，请执行以下操作：TYPE1 name1 name2 name<#>。
例子：kubectl get pod example-pod1 example-pod2

分别指定多个资源类型：TYPE1/name1 TYPE1/name2 TYPE2/name3 TYPE<#>/name<#>。
例子：kubectl get pod/example-pod1 replicationcontroller/example-rc1

3.2 kubectl格式化输出

kubectl格式化输出语法：kubectl [command] [TYPE] [NAME] -o <output_format>

输出格式	描述
-o custom-columns=spec	使用逗号分隔的自定义列列表打印表。
-o custom-columns-file=filename	使用 filename文件中的自定义列模板打印表。
-o json	输出 JSON 格式的 API 对象
-o jsonpath=template	打印 jsonpath 表达式定义的字段
-o jsonpath-file=filename	打印 filename>文件中 jsonpath 表达式定义的字段。
-o name	仅打印资源名称而不打印任何其他内容。
-o wide	以纯文本格式输出，包含所有附加信息。对于 Pod 包含节点名。
-o yaml	输出 YAML 格式的 API 对象。

四.kubectl常用命令

查看从什么地址能访问k8s API，会显示k8s集群的master节点的地址

[root@k8scloude1 ~]# kubectl cluster-info 
Kubernetes control plane is running at https://192.168.110.130:6443
CoreDNS is running at https://192.168.110.130:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

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

查看kubectl版本

[root@k8scloude1 ~]# kubectl version 
Client Version: version.Info{Major:"1", Minor:"21", GitVersion:"v1.21.0", GitCommit:"cb303e613a121a29364f75cc67d3d580833a7479", GitTreeState:"clean", BuildDate:"2021-04-08T16:31:21Z", GoVersion:"go1.16.1", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"21", GitVersion:"v1.21.0", GitCommit:"cb303e613a121a29364f75cc67d3d580833a7479", GitTreeState:"clean", BuildDate:"2021-04-08T16:25:06Z", GoVersion:"go1.16.1", Compiler:"gc", Platform:"linux/amd64"}

[root@k8scloude1 ~]# kubectl version --short
Client Version: v1.21.0
Server Version: v1.21.0

查看k8s的pod网段，可以看到pod网段为10.244.0.0/16

#查看初始化时候的k8s集群配置:kubeadm config view
[root@k8scloude1 ~]# kubeadm config view
Command "view" is deprecated, This command is deprecated and will be removed in a future release, please use 'kubectl get cm -o yaml -n kube-system kubeadm-config' to get the kubeadm config directly.
apiServer:
  extraArgs:
    authorization-mode: Node,RBAC
  timeoutForControlPlane: 4m0s
apiVersion: kubeadm.k8s.io/v1beta2
certificatesDir: /etc/kubernetes/pki
clusterName: kubernetes
controllerManager: {}
dns:
  type: CoreDNS
etcd:
  local:
    dataDir: /var/lib/etcd
imageRepository: registry.aliyuncs.com/google_containers
kind: ClusterConfiguration
kubernetesVersion: v1.21.0
networking:
  dnsDomain: cluster.local
  podSubnet: 10.244.0.0/16
  serviceSubnet: 10.96.0.0/12
scheduler: {}

查看kubeconfig文件的结构

[root@k8scloude1 ~]# kubectl config view
apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: DATA+OMITTED
    server: https://192.168.110.130:6443
  name: kubernetes
contexts:
- context:
    cluster: kubernetes
    user: kubernetes-admin
  name: kubernetes-admin@kubernetes
current-context: kubernetes-admin@kubernetes
kind: Config
preferences: {}
users:
- name: kubernetes-admin
  user:
    client-certificate-data: REDACTED
    client-key-data: REDACTED

五.查看kubernetes集群node节点和pod负载

5.1 安装metric-server

查看node节点和pod的负载，发现看不了node和pod的负载，是因为没有安装metric-server

[root@k8scloude1 ~]# kubectl top nodes
W0109 16:45:38.197980   75467 top_node.go:119] Using json format to get metrics. Next release will switch to protocol-buffers, switch early by passing --use-protocol-buffers flag
error: Metrics API not available

[root@k8scloude1 ~]# kubectl top pods
W0109 16:45:58.436117   75718 top_pod.go:140] Using json format to get metrics. Next release will switch to protocol-buffers, switch early by passing --use-protocol-buffers flag
error: Metrics API not available

为了查看节点和pod的负载，下面开始安装metric-server

创建目录，用来存放metric-server

[root@k8scloude1 ~]# mkdir metric-server

[root@k8scloude1 ~]# cd metric-server/

下载metrics-server并解压

[root@k8scloude1 metric-server]# wget https://github.com/kubernetes-sigs/metrics-server/archive/v0.3.6.tar.gz

[root@k8scloude1 metric-server]# ls
v0.3.6.tar.gz

[root@k8scloude1 metric-server]# tar xf v0.3.6.tar.gz 

[root@k8scloude1 metric-server]# ls
metrics-server-0.3.6  v0.3.6.tar.gz

[root@k8scloude1 metric-server]# cd metrics-server-0.3.6/

[root@k8scloude1 metrics-server-0.3.6]# ls
cmd  code-of-conduct.md  CONTRIBUTING.md  deploy  Gopkg.lock  Gopkg.toml  hack  LICENSE  Makefile  OWNERS  OWNERS_ALIASES  pkg  README.md  SECURITY_CONTACTS  vendor  version

[root@k8scloude1 metrics-server-0.3.6]# cd deploy/

[root@k8scloude1 deploy]# ls
1.7  1.8+  docker  minikube

[root@k8scloude1 deploy]# cd 1.8+

[root@k8scloude1 1.8+]# ls
aggregated-metrics-reader.yaml  auth-delegator.yaml  auth-reader.yaml  metrics-apiservice.yaml  metrics-server-deployment.yaml  metrics-server-service.yaml  resource-reader.yaml

查看需要下载的镜像，image: k8s.gcr.io/metrics-server-amd64:v0.3.6这个镜像国内访问不了，我们手动下载一个国内镜像

[root@k8scloude1 1.8+]# grep image metrics-server-deployment.yaml
      # mount in tmp so we can safely use from-scratch images and/or read-only containers
        image: k8s.gcr.io/metrics-server-amd64:v0.3.6
        imagePullPolicy: Always

在k8s集群master节点和worker节点都需要下载metrics-server-amd64:v0.3.6镜像

[root@k8scloude1 1.8+]# docker pull mirrorgooglecontainers/metrics-server-amd64:v0.3.6

[root@k8scloude1 1.8+]# docker images | grep mirrorgooglecontainers
REPOSITORY                                                        TAG        IMAGE ID       CREATED         SIZE
mirrorgooglecontainers/metrics-server-amd64                       v0.3.6     9dd718864ce6   2 years ago     39.9MB

镜像已经下好了，现在进行docker tag重命名，并删除原镜像mirrorgooglecontainers/metrics-server-amd64:v0.3.6

[root@k8scloude1 1.8+]# docker tag mirrorgooglecontainers/metrics-server-amd64:v0.3.6 k8s.gcr.io/metrics-server-amd64:v0.3.6

[root@k8scloude1 1.8+]# docker rmi mirrorgooglecontainers/metrics-server-amd64:v0.3.6

worker节点也进行相同操作

[root@k8scloude2 ~]# docker pull mirrorgooglecontainers/metrics-server-amd64:v0.3.6

[root@k8scloude2 ~]# docker tag mirrorgooglecontainers/metrics-server-amd64:v0.3.6 k8s.gcr.io/metrics-server-amd64:v0.3.6

[root@k8scloude2 ~]# docker rmi mirrorgooglecontainers/metrics-server-amd64:v0.3.6

[root@k8scloude3 ~]# docker pull mirrorgooglecontainers/metrics-server-amd64:v0.3.6

[root@k8scloude3 ~]# docker tag mirrorgooglecontainers/metrics-server-amd64:v0.3.6 k8s.gcr.io/metrics-server-amd64:v0.3.6

[root@k8scloude3 ~]# docker rmi mirrorgooglecontainers/metrics-server-amd64:v0.3.6

修改配置文件，镜像下载策略imagePullPolicy改为IfNotPresent，IfNotPresent表示只有当镜像在本地不存在时才会拉取

[root@k8scloude1 1.8+]# pwd
/root/metric-server/metrics-server-0.3.6/deploy/1.8+

#修改内容如下： imagePullPolicy: IfNotPresent
#        command:
#      - /metrics-server
#        - --metric-resolution=30s
#        - --kubelet-insecure-tls
#        - --kubelet-preferred-address-types=InternalIP
[root@k8scloude1 1.8+]# tail -20 metrics-server-deployment.yaml
        k8s-app: metrics-server
    spec:
      serviceAccountName: metrics-server
      volumes:
      # mount in tmp so we can safely use from-scratch images and/or read-only containers
      - name: tmp-dir
        emptyDir: {}
      containers:
      - name: metrics-server
        image: k8s.gcr.io/metrics-server-amd64:v0.3.6
        imagePullPolicy: IfNotPresent
        command:
        - /metrics-server
        - --metric-resolution=30s
        - --kubelet-insecure-tls
        - --kubelet-preferred-address-types=InternalIP
        volumeMounts:
        - name: tmp-dir
          mountPath: /tmp

安装metrics-server

#kubectl apply -f .    .表示安装当前目录下的所有文件
[root@k8scloude1 1.8+]# kubectl apply -f .
clusterrole.rbac.authorization.k8s.io/system:aggregated-metrics-reader created
Warning: rbac.authorization.k8s.io/v1beta1 ClusterRoleBinding is deprecated in v1.17+, unavailable in v1.22+; use rbac.authorization.k8s.io/v1 ClusterRoleBinding
clusterrolebinding.rbac.authorization.k8s.io/metrics-server:system:auth-delegator created
Warning: rbac.authorization.k8s.io/v1beta1 RoleBinding is deprecated in v1.17+, unavailable in v1.22+; use rbac.authorization.k8s.io/v1 RoleBinding
rolebinding.rbac.authorization.k8s.io/metrics-server-auth-reader created
Warning: apiregistration.k8s.io/v1beta1 APIService is deprecated in v1.19+, unavailable in v1.22+; use apiregistration.k8s.io/v1 APIService
apiservice.apiregistration.k8s.io/v1beta1.metrics.k8s.io created
serviceaccount/metrics-server created
deployment.apps/metrics-server created
service/metrics-server created
clusterrole.rbac.authorization.k8s.io/system:metrics-server created
clusterrolebinding.rbac.authorization.k8s.io/system:metrics-server created

查看所有的命名空间

[root@k8scloude1 1.8+]# kubectl get ns
NAME              STATUS   AGE
default           Active   18h
kube-node-lease   Active   18h
kube-public       Active   18h
kube-system       Active   18h

当观察到metrics-server-bcfb98c76-k5dmj状态为Running，metrics-server服务就正常启动了

[root@k8scloude1 1.8+]# kubectl get pod -n kube-system -o wide
NAME                                       READY   STATUS    RESTARTS   AGE   IP                NODE         NOMINATED NODE   READINESS GATES
calico-kube-controllers-6b9fbfff44-4jzkj   1/1     Running   2          19h   10.244.251.194    k8scloude3   <none>           <none>
calico-node-bdlgm                          1/1     Running   1          19h   192.168.110.130   k8scloude1   <none>           <none>
calico-node-hx8bk                          1/1     Running   1          19h   192.168.110.128   k8scloude3   <none>           <none>
calico-node-nsbfs                          1/1     Running   1          19h   192.168.110.129   k8scloude2   <none>           <none>
coredns-545d6fc579-7wm95                   1/1     Running   1          19h   10.244.158.68     k8scloude1   <none>           <none>
coredns-545d6fc579-87q8j                   1/1     Running   1          19h   10.244.158.67     k8scloude1   <none>           <none>
etcd-k8scloude1                            1/1     Running   1          19h   192.168.110.130   k8scloude1   <none>           <none>
kube-apiserver-k8scloude1                  1/1     Running   1          19h   192.168.110.130   k8scloude1   <none>           <none>
kube-controller-manager-k8scloude1         1/1     Running   1          19h   192.168.110.130   k8scloude1   <none>           <none>
kube-proxy-599xh                           1/1     Running   1          19h   192.168.110.128   k8scloude3   <none>           <none>
kube-proxy-lpj8z                           1/1     Running   1          19h   192.168.110.129   k8scloude2   <none>           <none>
kube-proxy-zxlk9                           1/1     Running   1          19h   192.168.110.130   k8scloude1   <none>           <none>
kube-scheduler-k8scloude1                  1/1     Running   1          19h   192.168.110.130   k8scloude1   <none>           <none>
metrics-server-bcfb98c76-k5dmj             1/1     Running   0          70s   10.244.112.131    k8scloude2   <none>           <none>

5.2 查看node负载

查看node的负载

[root@k8scloude1 1.8+]# kubectl top node 
W0110 11:37:47.025099   75026 top_node.go:119] Using json format to get metrics. Next release will switch to protocol-buffers, switch early by passing --use-protocol-buffers flag
NAME         CPU(cores)   CPU%   MEMORY(bytes)   MEMORY%   
k8scloude1   257m         12%    1487Mi          45%       
k8scloude2   104m         5%     698Mi           36%       
k8scloude3   102m         5%     701Mi           36%

5.3 查看pod负载

查看pod的负载

注释：一核心分成1000个微核心m 1核=1000m

[root@k8scloude1 1.8+]# kubectl top pods
W0110 11:38:40.576780   75696 top_pod.go:140] Using json format to get metrics. Next release will switch to protocol-buffers, switch early by passing --use-protocol-buffers flag
No resources found in default namespace.

#-A表示所有命名空间
[root@k8scloude1 1.8+]# kubectl top pods -A
W0110 11:38:47.276962   75784 top_pod.go:140] Using json format to get metrics. Next release will switch to protocol-buffers, switch early by passing --use-protocol-buffers flag
NAMESPACE     NAME                                       CPU(cores)   MEMORY(bytes)   
kube-system   calico-kube-controllers-6b9fbfff44-4jzkj   2m           25Mi            
kube-system   calico-node-bdlgm                          37m          170Mi           
kube-system   calico-node-hx8bk                          43m          157Mi           
kube-system   calico-node-nsbfs                          56m          164Mi           
kube-system   coredns-545d6fc579-7wm95                   3m           18Mi            
kube-system   coredns-545d6fc579-87q8j                   3m           18Mi            
kube-system   etcd-k8scloude1                            14m          91Mi            
kube-system   kube-apiserver-k8scloude1                  60m          351Mi           
kube-system   kube-controller-manager-k8scloude1         21m          56Mi            
kube-system   kube-proxy-599xh                           1m           24Mi            
kube-system   kube-proxy-lpj8z                           1m           24Mi            
kube-system   kube-proxy-zxlk9                           1m           24Mi            
kube-system   kube-scheduler-k8scloude1                  3m           23Mi            
kube-system   metrics-server-bcfb98c76-k5dmj             1m           13Mi

六.命名空间namespace的管理

6.1 何为命名空间namespace

在 Kubernetes 中，命名空间（Namespace）提供一种机制，将同一集群中的资源划分为相互隔离的组。同一命名空间内的资源名称要唯一，但跨命名空间时没有这个要求。命名空间作用域仅针对带有命名空间的对象，例如 Deployment、Service 等，这种作用域对集群访问的对象不适用，例如 StorageClass、Node、PersistentVolume 等。

6.2 管理命名空间namespace

查看所有的命名空间

[root@k8scloude1 1.8+]# kubectl get namespaces 
NAME              STATUS   AGE
default           Active   19h
kube-node-lease   Active   19h
kube-public       Active   19h
kube-system       Active   19h

[root@k8scloude1 1.8+]# kubectl get ns
NAME              STATUS   AGE
default           Active   19h
kube-node-lease   Active   19h
kube-public       Active   19h
kube-system       Active   19h

创建命名空间，注意：不同的namespace之间相互隔离

[root@k8scloude1 1.8+]# kubectl create ns ns1
namespace/ns1 created

[root@k8scloude1 1.8+]# kubectl create ns ns2
namespace/ns2 created

[root@k8scloude1 1.8+]# kubectl get ns
NAME              STATUS   AGE
default           Active   19h
kube-node-lease   Active   19h
kube-public       Active   19h
kube-system       Active   19h
ns1               Active   6s
ns2               Active   4s

获取全局上下文，可以看到当前命名空间为default

[root@k8scloude1 ~]# kubectl config get-contexts 
CURRENT   NAME                          CLUSTER      AUTHINFO           NAMESPACE
*         kubernetes-admin@kubernetes   kubernetes   kubernetes-admin   default

切换命名空间

#切换命名空间
[root@k8scloude1 ~]# kubectl config set-context --current --namespace=kube-system
Context "kubernetes-admin@kubernetes" modified.

[root@k8scloude1 ~]# kubectl config get-contexts 
CURRENT   NAME                          CLUSTER      AUTHINFO           NAMESPACE
*         kubernetes-admin@kubernetes   kubernetes   kubernetes-admin   kube-system

#获取当前K8S上下文
[root@k8scloude1 ~]# kubectl config current-context 
kubernetes-admin@kubernetes

6.2 使用kubens管理命名空间namespace

默认的切换命名空间的命令不好用，可以使用第三方的命名空间切换工具：kubens，kubens命令所在的网站为：https://github.com/ahmetb/kubectx/releases/

下载kubens，并授予可执行权限

[root@k8scloude1 ~]# wget https://github.com/ahmetb/kubectx/releases/download/v0.9.4/kubens

[root@k8scloude1 ~]# ll -h kubens 
-rw-r--r-- 1 root root 5.5K 12月  8 15:46 kubens

[root@k8scloude1 ~]# chmod +x kubens 

[root@k8scloude1 ~]# mv kubens /bin/

[root@k8scloude1 ~]# ls /bin/kubens 
/bin/kubens

查看所有的命名空间

[root@k8scloude1 ~]# kubens 
default
kube-node-lease
kube-public
kube-system
ns1
ns2

切换namespace

#切换namespace到kube-system
[root@k8scloude1 ~]# kubens kube-system
Context "kubernetes-admin@kubernetes" modified.
Active namespace is "kube-system".

#此时，默认查询的就是kube-system命名空间下的pod
[root@k8scloude1 ~]# kubectl get pods -o wide
NAME                                       READY   STATUS    RESTARTS   AGE   IP                NODE         NOMINATED NODE   READINESS GATES
calico-kube-controllers-6b9fbfff44-4jzkj   1/1     Running   2          20h   10.244.251.194    k8scloude3   <none>           <none>
calico-node-bdlgm                          1/1     Running   1          20h   192.168.110.130   k8scloude1   <none>           <none>
calico-node-hx8bk                          1/1     Running   1          20h   192.168.110.128   k8scloude3   <none>           <none>
calico-node-nsbfs                          1/1     Running   1          20h   192.168.110.129   k8scloude2   <none>           <none>
coredns-545d6fc579-7wm95                   1/1     Running   1          20h   10.244.158.68     k8scloude1   <none>           <none>
coredns-545d6fc579-87q8j                   1/1     Running   1          20h   10.244.158.67     k8scloude1   <none>           <none>
etcd-k8scloude1                            1/1     Running   1          20h   192.168.110.130   k8scloude1   <none>           <none>
kube-apiserver-k8scloude1                  1/1     Running   1          20h   192.168.110.130   k8scloude1   <none>           <none>
kube-controller-manager-k8scloude1         1/1     Running   1          20h   192.168.110.130   k8scloude1   <none>           <none>
kube-proxy-599xh                           1/1     Running   1          20h   192.168.110.128   k8scloude3   <none>           <none>
kube-proxy-lpj8z                           1/1     Running   1          20h   192.168.110.129   k8scloude2   <none>           <none>
kube-proxy-zxlk9                           1/1     Running   1          20h   192.168.110.130   k8scloude1   <none>           <none>
kube-scheduler-k8scloude1                  1/1     Running   1          20h   192.168.110.130   k8scloude1   <none>           <none>
metrics-server-bcfb98c76-k5dmj             1/1     Running   0          56m   10.244.112.131    k8scloude2   <none>           <none>

切换namespace到default

#切换namespace到default
[root@k8scloude1 ~]# kubens default
Context "kubernetes-admin@kubernetes" modified.
Active namespace is "default".

#此时，默认查询的就是default命名空间下的pod
[root@k8scloude1 ~]# kubectl get pods -o wide
No resources found in default namespace.

#要查询kube-public命名空间下的pod，使用-n kube-public指定
[root@k8scloude1 ~]# kubectl get pods -n kube-public
No resources found in kube-public namespace.

使用kubectl管理Kubernetes(k8s)集群：常用命令，查看负载，命名空间namespace管理 -...

一.系统环境

三.kubectl

3.1 kubectl语法

3.2 kubectl格式化输出

四.kubectl常用命令

五.查看kubernetes集群node节点和pod负载

5.1 安装metric-server

5.2 查看node负载

5.3 查看pod负载

六.命名空间namespace的管理

6.1 何为命名空间namespace

6.2 管理命名空间namespace

6.2 使用kubens管理命名空间namespace

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