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kubernetes学习笔记

基础环境

系统镜像版本

  • Centos 7.6 最小化

最低运行环境基本要求

  • 内存及CPU：512MB / CPU 1核

K3s版本

  • v1.30.0+k3s1

集群规划:

注意：需要对每台主机设置hostname,使用hostnamectl set-hostname 主机名

  • K8s-master 192.168.200.129 1C/1G
  • K8s-worker1 192.168.200.130 2C/2G
  • K8s-worker2 192.168.200.131 2C/2G

准备工作

  1. 关闭防火墙

systemctl disable firewalld --now

  1. 设置Selinux(需要接入互联网)

yum install -y container-selinux selinux-policy-base yum install -y https://rpm.rancher.io/k3s/latest/common/centos/7/noarch/k3s-selinux-0.2-1.el7_8.noarch.rpm

  1. 免密登录
ssh-keygen -t rsa
ssh-copy-id -i /root/.ssh/id_rsa.pub 192.168.200.130
ssh-copy-id -i /root/.ssh/id_rsa.pub 192.168.200.131

安装K3s集群

K3s集群分为K3s server（控制平面） 及 k3s agent （工作节点）

  • 在k8s-master 节点安装k3s server
curl -sfL https://rancher-mirror.rancher.cn/k3s/k3s-install.sh | INSTALL_K3S_MIRROR=cn sh -

卸载K3s集群

k3s-uninstall.sh

验证安装

  • 查看节点状态 kubectl get node
[root@localhost ~]# kubectl get node
NAME         STATUS   ROLES                  AGE   VERSION
k8s-master   Ready    control-plane,master   16s   v1.30.4+k3s1
  • 查看token cat /var/lib/rancher/k3s/server/node-token

这个token用于K8s-worker1和K8s-worker2这两个节点加入集群

[root@localhost ~]# cat /var/lib/rancher/k3s/server/node-token
K103b59c9e5e4a8904ad2f4ba0dc2fc17079af59e8cd3f8f7c51f5a42d62a373eb0::server:e2b46796a195fe2a86de36c54855802e

节点加入集群

分别在k8s-worker1 和 k8s-worker2 两台主机分别执行以下命令

curl -sfL https://rancher-mirror.rancher.cn/k3s/k3s-install.sh | INSTALL_K3S_MIRROR=cn K3S_URL=https://192.168.200.129:6443 K3S_TOKEN=K103b59c9e5e4a8904ad2f4ba0dc2fc17079af59e8cd3f8f7c51f5a42d62a373eb0::server:e2b46796a195fe2a86de36c54855802e sh -

在k8s-master节点执行kubectl get node，可以看到k8s-worker1 和 k8s-worker2 已经加入集群

[root@k8s-master ~]# kubectl get node
NAME          STATUS   ROLES                  AGE     VERSION
k8s-master    Ready    control-plane,master   57m     v1.30.4+k3s1
k8s-worker1   Ready    <none>                 4m46s   v1.30.4+k3s1
k8s-worker2   Ready    <none>                 3m33s   v1.30.4+k3s1

镜像加速

  1. k8s-master节点添加镜像加速配置文件 /etc/rancher/k3s/registries.yaml
mirrors:
  docker.io:
    endpoint:
      - "https://hub.uuuadc.top"
      - "https://docker.anyhub.us.kg"
      - "https://dockerhub.jobcher.com"
      - "https://dockerhub.icu"
      - "https://docker.ckyl.me"
      - "https://docker.awsl9527.cn"
  1. 分发到k8s-worker1 和 k8s-worker2 
scp /etc/rancher/k3s/registries.yaml root@192.168.200.130:/etc/rancher/k3s/registries.yaml
scp /etc/rancher/k3s/registries.yaml root@192.168.200.131:/etc/rancher/k3s/registries.yaml
  1. 重启k3s-server及k3s-agent
# 在k8s-master节点执行
systemctl restart k3s
# 在k8s-worker1和k8s-worker2节点执行
systemctl restart k3s-agent
  1. 验证
# 拉取mysql镜像
[root@k8s-master ~]# crictl pull mysql:5.7-debian
Image is up to date for sha256:6dca1336186922918678a49811059c4f6bfa1759d853a4e7cde904879d2e9b83
# 查看镜像列表
[root@k8s-master ~]# crictl  images
IMAGE                     TAG                 IMAGE ID            SIZE
docker.io/library/mysql   5.7-debian          6dca133618692       163MB

## Pod

  • 创建Pod资源 kubectl run
# 创建一个名称为 mynginx，镜像为 nginx 的Pod
[root@k8s-master ~]# kubectl run mynginx --image=nginx
pod/mynginx created
  • 查看Pod kubectl get pod
[root@k8s-master ~]# kubectl get pod
NAME      READY   STATUS    RESTARTS   AGE
mynginx   1/1     Running   0          11m
# 显示pod的IP和运行节点信息
[root@k8s-master ~]# kubectl get pod -owide
NAME      READY   STATUS    RESTARTS   AGE     IP          NODE          NOMINATED NODE   READINESS GATES
mynginx   1/1     Running   0          4m40s   10.42.2.3   k8s-worker2   <none>           <none>
  • 查看Pod运行日志 kubectl logs
[root@k8s-master ~]# kubectl logs mynginx
/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/
/docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh
10-listen-on-ipv6-by-default.sh: info: Getting the checksum of /etc/nginx/conf.d/default.conf
10-listen-on-ipv6-by-default.sh: info: Enabled listen on IPv6 in /etc/nginx/conf.d/default.conf
/docker-entrypoint.sh: Sourcing /docker-entrypoint.d/15-local-resolvers.envsh
/docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh
/docker-entrypoint.sh: Launching /docker-entrypoint.d/30-tune-worker-processes.sh
/docker-entrypoint.sh: Configuration complete; ready for start up
2024/08/24 05:50:48 [notice] 1#1: using the "epoll" event method
2024/08/24 05:50:48 [notice] 1#1: nginx/1.27.1
2024/08/24 05:50:48 [notice] 1#1: built by gcc 12.2.0 (Debian 12.2.0-14) 
2024/08/24 05:50:48 [notice] 1#1: OS: Linux 3.10.0-1160.el7.x86_64
2024/08/24 05:50:48 [notice] 1#1: getrlimit(RLIMIT_NOFILE): 1048576:1048576
2024/08/24 05:50:48 [notice] 1#1: start worker processes
2024/08/24 05:50:48 [notice] 1#1: start worker process 29
2024/08/24 05:50:48 [notice] 1#1: start worker process 30
2024/08/24 05:50:48 [notice] 1#1: start worker process 31
2024/08/24 05:50:48 [notice] 1#1: start worker process 32
10.42.0.0 - - [24/Aug/2024:05:51:59 +0000] "GET / HTTP/1.1" 200 615 "-" "curl/7.29.0" "-"
  • 查看Pod详细信息
[root@k8s-master ~]# kubectl describe pod mynginx
Name:             mynginx
Namespace:        default
Priority:         0
Service Account:  default
Node:             k8s-worker2/192.168.200.131
Start Time:       Sat, 24 Aug 2024 13:46:18 +0800
Labels:           run=mynginx
Annotations:      <none>
Status:           Pending
IP:               
IPs:              <none>
Containers:
  mynginx:
    Container ID:   
    Image:          nginx
    Image ID:       
    Port:           <none>
    Host Port:      <none>
    State:          Waiting
      Reason:       ContainerCreating
    Ready:          False
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-w4xqw (ro)
Conditions:
  Type                        Status
  PodReadyToStartContainers   False 
  Initialized                 True 
  Ready                       False 
  ContainersReady             False 
  PodScheduled                True 
Volumes:
  kube-api-access-w4xqw:
    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  Scheduled  13s   default-scheduler  Successfully assigned default/mynginx to k8s-worker2
  • 在容器中执行命令 kubectl exec
kubectl exec mynginx -it -- /bin/bash
  • 删除Pod kubectl delete
# 删除Pod
kubectl delete pod mynginx
# 强制删除
kubectl delete pod mynginx --force

Deployment与ReplicaSet

  • Deployment使Pod具有自愈的能力，当我们删除Deployment中的一个或多个pod后，他会自动创建Pod直到与副本数量一致
  • Deployment使Pod具有滚动更新及版本回退的能力
  • 创建Deployment kubectl create deployment
# 创建一个deployment资源，名称为nginx-deployment，镜像为nginx:1.22 ，副本数量为3
[root@k8s-master ~]# kubectl create deployment nginx-deployment --image=nginx:1.22 --replicas=3
deployment.apps/nginx-deployment created
  • 查看Deployment
[root@k8s-master ~]# kubectl get deploy 
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   3/3     3            3           5m9s
  • 查看Pod
[root@k8s-master ~]# kubectl get pod
NAME                                READY   STATUS    RESTARTS   AGE
mynginx                             1/1     Running   0          28m
nginx-deployment-645dcd4477-87twt   1/1     Running   0          5m58s
nginx-deployment-645dcd4477-9xb9p   1/1     Running   0          5m58s
nginx-deployment-645dcd4477-j9xt8   1/1     Running   0          5m58s
  • 查看Deployment的副本数量 kubectl get replicaSet
[root@k8s-master ~]# kubectl get replicaSet
NAME                          DESIRED   CURRENT   READY   AGE
nginx-deployment-645dcd4477   3         3         3       6m36s
  • 手动扩缩容 kubectl scale deploy 资源名称 --replicas=数量
# 将deployment/nginx-deployment的副本集扩充到5个
[root@k8s-master ~]# kubectl scale deployment/nginx-deployment --replicas=5
deployment.apps/nginx-deployment scaled
# 查看扩缩后的Pod
[root@k8s-master ~]# kubectl get pod
NAME                                READY   STATUS    RESTARTS   AGE
mynginx                             1/1     Running   0          36m
nginx-deployment-645dcd4477-87twt   1/1     Running   0          13m
nginx-deployment-645dcd4477-9xb9p   1/1     Running   0          13m
nginx-deployment-645dcd4477-df828   1/1     Running   0          19s
nginx-deployment-645dcd4477-j9xt8   1/1     Running   0          13m
nginx-deployment-645dcd4477-t4cw5   1/1     Running   0          19s
  • 自动扩缩容 kubectl autoscale 资源名称 --min=最小pod数 --max=最大pod数 扩缩容条件

扩缩容条件参考：https://github.com/kubernetes-sigs/metrics-server#readme

#自动缩放，设置deployment/nginx-deployment为自动扩缩容，最小数量为3个pod，最大为10个pod，扩缩容的条件是所有pod的平均cpu使用率不超过75%
[root@k8s-master ~]# kubectl autoscale deployment/nginx-deployment --min=3 --max=10 --cpu-percent=75 
horizontalpodautoscaler.autoscaling/nginx-deployment autoscaled
  • 滚动更新

注意：在滚动更新的过程中会出现新旧服务共存在的状态

# 设定deployment/nginx-deployment的镜像为nginx:1.23版本
[root@k8s-master ~]# kubectl set image deployment/nginx-deployment nginx=nginx:1.23
deployment.apps/nginx-deployment image updated
#滚动更新状态
kubectl rollout status deployment/nginx-deployment
#查看过程
kubectl get rs --watch
  • 查看历史版本 kubectl rollout history
[root@k8s-master ~]# kubectl rollout history deployment/nginx-deployment
deployment.apps/nginx-deployment 
REVISION  CHANGE-CAUSE
1         <none>
2         <none>
  • 查看指定版本 kubectl rollout history deployment资源名称 --revision=版本号
[root@k8s-master ~]# kubectl rollout history deployment/nginx-deployment --revision=2
deployment.apps/nginx-deployment with revision #2
Pod Template:
  Labels:   app=nginx-deployment
  pod-template-hash=5cf4667cdb
  Containers:
    nginx:
    Image:  nginx:1.23
    Port:   <none>
    Host Port:  <none>
    Environment:    <none>
    Mounts: <none>
  Volumes:  <none>
  Node-Selectors:   <none>
  Tolerations:  <none>
  • 回滚到历史版本 kubectl rollout undo deployment资源名称 --to-revision=版本号
[root@k8s-master ~]# kubectl rollout undo deployment/nginx-deployment --to-revision=1
deployment.apps/nginx-deployment rolled back

Service

Service会将将运行在一组Pod上的应用公开为网络服务，并为该组Pod提供相同的DNS名称，进行负载均衡。Kubernetes 为 Pod 提供分配了IP 地址，但IP地址可能会发生变化。Service会使集群内的容器可以通过service名称访问服务，而不需要担心Pod的IP发生变化。

image.png

  • 创建Service资源

ServiceType 取值

  • ClusterIP：将服务公开在集群内部。kubernetes会给服务分配一个集群内部的 IP，集群内的所有主机都可以通过这个Cluster-IP访问服务。集群内部的Pod可以通过service名称访问服务。
  • NodePort：通过每个节点的主机IP 和静态端口（NodePort）暴露服务。 集群的外部主机可以使用节点IP和NodePort访问服务。
  • ExternalName：将集群外部的网络引入集群内部。
  • LoadBalancer：使用云提供商的负载均衡器向外部暴露服务。

``` # 创建一个名称为nginx-service的Service，使用的资源为deployment/nginx-deployment，集群内部暴露的端口为8080，目标端口为80,这个服务只能在集群内部访问，无法在外部访问 [root@k8s-master ~]# kubectl expose deployment/nginx-deployment --name nginx-service --port=8080 --target-port=80 service/nginx-service exposed

# 创建一个名称为nginx-service的Service，使用的资源为deployment/nginx-deployment，对外暴露的端口为8081，目标端口为80 [root@k8s-master ~]# kubectl expose deployment/nginx-deployment --name=nginx-outside --type=NodePort --port=8081 --target-port=80 service/nginx-outside exposed ```

  • 查看Service kubectl get service

``` # nginx-outside暴露了两个端口，8081是集群内部访问的端口，31606是外部访问的端口（http://192.168.200.129:31606） [root@k8s-master ~]# kubectl get service NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.43.0.1 443/TCP 178m nginx-outside NodePort 10.43.151.51 8081:31606/TCP 7s nginx-service ClusterIP 10.43.21.154 8080/TCP 2m41s

# 通过集群分配的ip+端口访问服务 [root@k8s-master ~]# curl 10.43.21.154:8080

Welcome to nginx!

Welcome to nginx!

If you see this page, the nginx web server is successfully installed and working. Further configuration is required.

For online documentation and support please refer to nginx.org.
Commercial support is available at nginx.com.

Thank you for using nginx.

# 通过--rm参数创建一个一次性的pod(退出pod后会自动销毁) [root@k8s-master ~]# kubectl run test -it --image=nginx:1.22 --rm -- bash If you don't see a command prompt, try pressing enter.

# 通过服务名称+端口进行访问 root@test:/# curl nginx-service:8080

Welcome to nginx!

Welcome to nginx!

If you see this page, the nginx web server is successfully installed and working. Further configuration is required.

For online documentation and support please refer to nginx.org.
Commercial support is available at nginx.com.

Thank you for using nginx.

```

  • 查看service详细信息 kubectl describe service 服务名称

[root@k8s-master ~]# kubectl describe service nginx-service Name: nginx-service Namespace: default Labels: app=nginx-deployment Annotations: <none> Selector: app=nginx-deployment Type: ClusterIP IP Family Policy: SingleStack IP Families: IPv4 IP: 10.43.21.154 IPs: 10.43.21.154 Port: <unset> 8080/TCP TargetPort: 80/TCP Endpoints: 10.42.0.11:80,10.42.1.8:80,10.42.1.9:80 + 2 more... # 负载均衡端点 Session Affinity: None Events: <none>

NameSpace

  • 查看命名空间 kubectl get namespace
  • default 默认的命名空间，不可删除，未指定命名空间的对象都会被分配到default中。
  • kube-system Kubernetes 系统对象(控制平面和Node组件)所使用的命名空间。
  • kube-public 自动创建的公共命名空间，所有用户（包括未经过身份验证的用户）都可以读取它。通常我们约定，将整个集群中公用的可见和可读的资源放在这个空间中。
  • kube-node-lease 租约（Lease）对象使用的命名空间。每个节点都有一个关联的 lease 对象，lease 是一种轻量级资源。lease对象通过发送心跳，检测集群中的每个节点是否发生故障。

[root@k8s-master ~]# kubectl get namespace NAME STATUS AGE default Active 3h19m kube-node-lease Active 3h19m kube-public Active 3h19m kube-system Active 3h19m

  • 创建命名空间 kubectl create namespace dev

在创建Pod的时候可以使用 -n 参数指定命名空间

[root@k8s-master ~]# kubectl create namespace dev namespace/dev created

  • 删除命名空间

    删除命名空间时会同步删除该命名空间下的资源

    [root@k8s-master ~]# kubectl delete namespace dev namespace "dev" deleted

  • 将dev设为当前命名空间，后续所有操作都在此命名空间下执行。

kubectl config set-context $(kubectl config current-context) --namespace=dev

通过声明式对象配置

  • 配置对象

    在创建的 Kubernetes 对象所对应的 yaml文件中，需要配置的字段如下：

    • apiVersion - Kubernetes API 的版本
    • kind - 对象类别，例如Pod、Deployment、Service、ReplicaSet等
    • metadata - 描述对象的元数据，包括一个 name 字符串、UID 和可选的 namespace
    • spec - 对象的配置

  • 栗子

这个配置文件中的Pod资源通常不需要单独定义，因为Pod将由Deployment自动创建和管理。Pod资源在这里是为了演示配置文件的结构，但在实际使用中，Deployment足以管理Pod的生命周期。

apiVersion: v1 # api版本信息
kind: Pod # 资源类型
metadata:
  name: nginx
  labels:
    app.kubernetes.io/name: proxy # 定义一个key为name，value为proxy的标签
spec:
  containers: # 下面为运行的容器列表
  - name: nginx # 容器名称
    image: nginx:1.22 # 镜像名称及版本号
    ports:
      - containerPort: 80 # 容器内部监听的端口
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment-demo # deployment资源名称
  labels:
    app: nginx  # 定义一个key为app，value为nginx的标签
spec:
  replicas: 3 # 指定副本数量为3个
  selector:
    matchLabels:
      app: nginx # 匹配标签key为app，value为nginx的所有资源
  template:
    metadata:
      labels:
        app: nginx # 定义一个key为app，value为nginx的标签
    spec:
      containers: # 下面为运行的容器列表
      - name: nginx # 容器名称
        image: nginx:1.22 # 镜像名称及版本号
        ports:
        - containerPort: 80 # 容器内部监听的端口
---
apiVersion: v1
kind: Service # 资源类型
metadata:
  name: nginx-service-demo # 定义服务名称
spec:
  selector:
    app: nginx # 匹配标签key为app，value为nginx的所有资源
  ports:
    - name: nginx-out-side 
      port: 80 # 集群内部暴露的端口
      nodePort: 31009 # 对外暴露的端口
      targetPort: 80 # 目标端口
  type: NodePort # 指定服务类型
  • 通过配置文件创建Pod
kubectl apply -f my-nginx.yaml
  • 通过配置文件删除Pod
kubectl delete -f my-nginx.yaml