k8s常用命令集合

0.前言

之前花了很长的时间部署了一个3节点的k8s集群，今天来总结一下k8s集群的常见命令，本次只讲一些简单且实用的命令，一些复杂的命令，像存储、网络、调度（污点、亲和性）等，后续会分开单独讲。

1.集群相关

1.1版本号

kubectl version

1.2集群信息

kubectl cluster-info 

查看集群基本信息，比如apiserver和coreDNS运行情况。

2.节点相关

2.1 查看所有节点

kubectl get node

可以看到每个节点的名称，运行状态，角色，运行时间和版本号。

2.2 单个节点详情

kubectl describe node k8s-master

Name:               k8s-master
Roles:              master
Labels:             beta.kubernetes.io/arch=amd64
                    beta.kubernetes.io/os=linux
                    kubernetes.io/arch=amd64
                    kubernetes.io/hostname=k8s-master
                    kubernetes.io/os=linux
                    node-role.kubernetes.io/master=
                    node.kubernetes.io/node=
Annotations:        node.alpha.kubernetes.io/ttl: 0
                    projectcalico.org/IPv4Address: 192.168.159.164/24
                    projectcalico.org/IPv4IPIPTunnelAddr: 172.30.235.192
                    volumes.kubernetes.io/controller-managed-attach-detach: true
CreationTimestamp:  Sat, 21 Sep 2024 16:44:40 +0800
Taints:             <none>
Unschedulable:      false
Lease:
  HolderIdentity:  k8s-master
  AcquireTime:     <unset>
  RenewTime:       Tue, 24 Sep 2024 11:40:36 +0800
Conditions:
  Type                 Status  LastHeartbeatTime                 LastTransitionTime                Reason                       Message
  ----                 ------  -----------------                 ------------------                ------                       -------
  NetworkUnavailable   False   Mon, 23 Sep 2024 18:06:35 +0800   Mon, 23 Sep 2024 18:06:35 +0800   CalicoIsUp                   Calico is running on this node
  MemoryPressure       False   Tue, 24 Sep 2024 11:37:39 +0800   Mon, 23 Sep 2024 17:57:54 +0800   KubeletHasSufficientMemory   kubelet has sufficient memory available
  DiskPressure         False   Tue, 24 Sep 2024 11:37:39 +0800   Mon, 23 Sep 2024 17:57:54 +0800   KubeletHasNoDiskPressure     kubelet has no disk pressure
  PIDPressure          False   Tue, 24 Sep 2024 11:37:39 +0800   Mon, 23 Sep 2024 17:57:54 +0800   KubeletHasSufficientPID      kubelet has sufficient PID available
  Ready                True    Tue, 24 Sep 2024 11:37:39 +0800   Mon, 23 Sep 2024 18:06:35 +0800   KubeletReady                 kubelet is posting ready status
Addresses:
  InternalIP:  192.168.159.164
  Hostname:    k8s-master
Capacity:
  cpu:                4
  ephemeral-storage:  17340Mi
  hugepages-1Gi:      0
  hugepages-2Mi:      0
  memory:             7837288Ki
  pods:               110
Allocatable:
  cpu:                4
  ephemeral-storage:  16364077029
  hugepages-1Gi:      0
  hugepages-2Mi:      0
  memory:             7734888Ki
  pods:               110
System Info:
  Machine ID:                 2785782508f543ab9ef0d544aa5cd429
  System UUID:                28ee4d56-b485-262e-304f-d352aae8a622
  Boot ID:                    f3ab19bb-b9f9-4c51-8e0d-323439f6c042
  Kernel Version:             5.14.0-427.13.1.el9_4.x86_64
  OS Image:                   Rocky Linux 9.4 (Blue Onyx)
  Operating System:           linux
  Architecture:               amd64
  Container Runtime Version:  containerd://1.7.22
  Kubelet Version:            v1.30.5
  Kube-Proxy Version:         v1.30.5
PodCIDR:                      172.30.0.0/24
PodCIDRs:                     172.30.0.0/24
Non-terminated Pods:          (3 in total)
  Namespace                   Name                                        CPU Requests  CPU Limits  Memory Requests  Memory Limits  Age
  ---------                   ----                                        ------------  ----------  ---------------  -------------  ---
  kube-system                 calico-kube-controllers-65dcc554ff-9pws2    0 (0%)        0 (0%)      0 (0%)           0 (0%)         17h
  kube-system                 calico-node-rccq4                           250m (6%)     0 (0%)      0 (0%)           0 (0%)         17h
  test                        busybox2                                    0 (0%)        0 (0%)      0 (0%)           0 (0%)         16h
Allocated resources:
  (Total limits may be over 100 percent, i.e., overcommitted.)
  Resource           Requests   Limits
  --------           --------   ------
  cpu                250m (6%)  0 (0%)
  memory             0 (0%)     0 (0%)
  ephemeral-storage  0 (0%)     0 (0%)
  hugepages-1Gi      0 (0%)     0 (0%)
  hugepages-2Mi      0 (0%)     0 (0%)
Events:              <none>

可以看到详细的节点信息，包括节点所在主机信息，节点运行情况和节点资源使用情况，当节点出现unready状态时，就可以使用该命令排查节点异常原因。

3.namespace相关

3.1 创建命令空间

kubectl create namespace test

test是namespace名称，可以自行指定。

3.2 查看namespace

kubectl get namespace/ns(简写)

注意： default namespace是一个很特殊的namespace，创建资源的时候不指定namespace的话，资源会默认创建在default namespace下,查找资源时。

3.3 查看指定namespace详情

kubectl describe ns test

4.pod相关

4.1 创建一个pod（以busybox为例）

（1）pod的声明文件

cd /data/yaml
cat busybox.yaml

apiVersion: v1
kind: Pod
metadata:
  name: busybox
  namespace: default
spec:
  containers:
  - name: busybox
    image: docker.m.daocloud.io/library/busybox
    command:
      - sleep
      - "3600"
    imagePullPolicy: IfNotPresent
  restartPolicy: Always

（2）创建pod

kubectl create -f busybox.yaml

4.2 查看所有pod

kubectl get pod -n default

可以看到pod运行情况，包括名称、pod就绪的数量，运行状态，重启次数和运行时间。

4.3 查看pod中应用日志

kubectl logs coredns-797bbb564b-whv9z -n kube-system

这里就可以看到coredns服务的日志信息。

4.4 pod中执行命令

（1）执行普通命令：

kubectl exec busybox -- echo hello

可以看到，会打印hello字符串。
在早期版本，可以通过以下命令进入到pod内部：

（2）进入Pod内部：

kubectl exec -it busybox /bin/sh

但是官方表示会移除该命令，推荐使用上述在pod内执行命令的方式。

4.5 查看pod详情

kubectl describe pod busybox -n default

Name:             busybox
Namespace:        default
Priority:         0
Service Account:  default
Node:             k8s-node2/192.168.159.166
Start Time:       Mon, 23 Sep 2024 18:43:39 +0800
Labels:           <none>
Annotations:      cni.projectcalico.org/containerID: f097a23677ace8e128cf0451171f7db9ce1c8637b6109ed05ecf3237e04dbf89
                  cni.projectcalico.org/podIP: 172.30.169.129/32
                  cni.projectcalico.org/podIPs: 172.30.169.129/32
Status:           Running
IP:               172.30.169.129
IPs:
  IP:  172.30.169.129
Containers:
  busybox:
    Container ID:  containerd://152f5039ba1d8c2f2d5c974e010316d969b27a923e3b3b539cff98ce39819731
    Image:         docker.m.daocloud.io/library/busybox
    Image ID:      docker.m.daocloud.io/library/busybox@sha256:c230832bd3b0be59a6c47ed64294f9ce71e91b327957920b6929a0caa8353140
    Port:          <none>
    Host Port:     <none>
    Command:
      sleep
      3600
    State:          Running
      Started:      Tue, 24 Sep 2024 15:04:41 +0800
    Last State:     Terminated
      Reason:       Completed
      Exit Code:    0
      Started:      Tue, 24 Sep 2024 13:40:11 +0800
      Finished:     Tue, 24 Sep 2024 15:04:40 +0800
    Ready:          True
    Restart Count:  4
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-frb2g (ro)
Conditions:
  Type                        Status
  PodReadyToStartContainers   True
  Initialized                 True
  Ready                       True
  ContainersReady             True
  PodScheduled                True
Volumes:
  kube-api-access-frb2g:
    Type:                    Projected (a volume that contains injected data from multiple sources)
    TokenExpirationSeconds:  3607
    ConfigMapName:           kube-root-ca.crt
    ConfigMapOptional:       <nil>
    DownwardAPI:             true
QoS Class:                   BestEffort
Node-Selectors:              <none>
Tolerations:                 node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                             node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type    Reason   Age                  From     Message
  ----    ------   ----                 ----     -------
  Normal  Created  13m (x5 over 20h)    kubelet  Created container busybox
  Normal  Started  13m (x5 over 20h)    kubelet  Started container busybox
  Normal  Pulled   13m (x4 over 5h17m)  kubelet  Container image "docker.m.daocloud.io/library/busybox" already present on machine

可以看到pod的详细信息，当pod状态异常的时候，基于pod详情可以快速排查pod异常的原因。

5.deployment相关

5.1 创建deployment

（1）deployment声明式文件

cd /data/yaml
cat nginx-deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: docker.m.daocloud.io/library/nginx
        ports:
        - containerPort: 80

（2）创建deployment:

kubectl apply -f nginx-deployment.yaml

5.2 查看deployment:

（1）查看deployment运行情况：

kubectl get deployment -n  default 

可以看到deploy名称，包含三个pod，且三个Pod准备就绪。

（2）查看replicaSet:

kubectl get replicaSet -n default

可以看到replicaSet的名称是deployment-随机编码，也即该replicaSet是关联之前创建的deployment的，这里显示用户期望pod数是3，当前运行数也是3，也即replicaSet正常运行。

（3）查看deployment对应pod:

kubectl get pod -n default |grep nginx

可以看到有3个pod分别运行在3个node上，这里之所以pod可以运行在master节点上，是因为现在没有给master节点加污点，pod可以调度到master节点上。

（4）查看deployment详情：

kubectl describe deployment nginx-deployment -n default

Name:                   nginx-deployment
Namespace:              default
CreationTimestamp:      Tue, 24 Sep 2024 15:37:54 +0800
Labels:                 app=nginx
Annotations:            deployment.kubernetes.io/revision: 1
Selector:               app=nginx
Replicas:               3 desired | 3 updated | 3 total | 3 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  app=nginx
  Containers:
   nginx:
    Image:         docker.m.daocloud.io/library/nginx
    Port:          80/TCP
    Host Port:     0/TCP
    Environment:   <none>
    Mounts:        <none>
  Volumes:         <none>
  Node-Selectors:  <none>
  Tolerations:     <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
  Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  <none>
NewReplicaSet:   nginx-deployment-846887469d (3/3 replicas created)
Events:
  Type    Reason             Age   From                   Message
  ----    ------             ----  ----                   -------
  Normal  ScalingReplicaSet  37m   deployment-controller  Scaled up replica set nginx-deployment-846887469d to 3

5.3 扩容deployment

kubectl scale nginx-deployment --replicas=4

如上命令，可以将nginx-deployment pod数扩容到4个，但是最好是在声明文件里面修改repica数，然后执行apply命令进行扩容。

5.4 deployment发布

deployment支持查看历史发布信息，并且支持回滚等操作，这些功能对于应用发布而言是非常重要的，所以官方也推荐以deployment的形式发布应用，而不是以pod的形式。
（1）查看所有deployment历史版本：

kubectl rollout history deployment -n default

（2）查看指定deployment历史版本：

kubectl rollout history deployment/nginx-deployment（deployment名称）-n default

（3）查看指定deployment指定历史版本详情：

kubectl rollout history deployment/nginx-deployment --revision=1（版本号）-n default

（4）回退到指定版本

kubectl rollout undo deployment/pc-deployment --to-revision=1 -n default

（5）查看回退状态

kubectl rollout status deploy/nginx-deployment -n default

5.5 删除deployment:

kubectl delete -f nginx-deployment.yaml

6.service相关

6.1 ClusterIP类型

（1）service声明文件：

cd /data/yaml
cat nginx-service-clusterIp.yaml

apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  selector:
    app: nginx
  ports:
    - protocol: TCP
      port: 8080
      targetPort: 80
  type: ClusterIP

service是根据seletor关键字选中pod的，我们这里填写的是app:nginx,对应的是nginx-deployment中pod的标签。

kubectl get pod -n default --show-labels |grep nginx

可以看到pod labels里面有app=nginx这一项。

修改三个pod中nginx首页显示信息：

kubectl exec -it nginx-deployment-846887469d-5hj5w /bin/bash
echo nginx1 > /usr/share/nginx/html/index.html
kubectl exec -it nginx-deployment-846887469d-bs5k8 /bin/bash
echo nginx2 > /usr/share/nginx/html/index.html
kubectl exec -it nginx-deployment-846887469d-n5p7d /bin/bash
echo nginx3 > /usr/share/nginx/html/index.html

（2）创建service

kubectl apply -f nginx-service-nodePort.yaml

（3）查看service

kubectl get svc

可以看到service对应的IP是10.96.208.179，我们请求这个IP的8080端口，请求就会转发给对应的pod。

curl 10.96.208.179:8080
nginx3
curl 10.96.208.179:8080
nginx1
curl 10.96.208.179:8080
nginx2

看结果，如我们所想，请求到了nginx-deployment的pod，并正常响应。

6.2 NodePort类型

（1）service声明文件如下：

cd /data/yaml
cat nginx-service-nodePort.yaml

apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  selector:
    app: nginx
  ports:
    - protocol: TCP
      port: 8080
      targetPort: 80
  type: NodePort

（2）创建service：

kubectl apply -f nginx-service-nodePort.yaml

（3）查看svc

kubectl get svc

可以看到service的IP地址是10.96.208.179，并有两个端口8080和30219，可以通过10.96.208.179:8080端口访问pod，也可以通过任意k8s节点IP和30219端口访问pod.。

curl 10.96.208.179:8080
nginx1
curl 10.96.208.179:8080
nginx2
curl 10.96.208.179:8080
nginx3

curl 192.168.159.164:30219
nginx1
curl 192.168.159.165:30219
nginx2
curl 192.168.159.166:30219
nginx3

可以看到请求成功，且正常响应。

7.总结

今天主要讲了集群、pod、deployment、service等资源管理相关的命令，其他组件管理命令也都差不多，就不一一列举了，实在遇到比较少见的命令，也可以到官网查看，学习官方手册并实践，是进步最快的方式，后续会慢慢讲解k8s中存储、调度、网络等方案，happy hacking。