595 lines
19 KiB
Markdown
595 lines
19 KiB
Markdown
<h2><center>kubernetes 实战</center></h2>
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------
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## 一：Namespace
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Namespace是kubernetes系统中的一种非常重要资源，它的主要作用是用来实现多套环境的资源隔离或者多租户的资源隔离。
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默认情况下，kubernetes集群中的所有的Pod都是可以相互访问的。但是在实际中，可能不想让两个Pod之间进行互相的访问，那此时就可以将两个Pod划分到不同的namespace下。kubernetes通过将集群内部的资源分配到不同的Namespace中，可以形成逻辑上的"组"，以方便不同的组的资源进行隔离使用和管理。
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可以通过kubernetes的授权机制，将不同的namespace交给不同租户进行管理，这样就实现了多租户的资源隔离。此时还能结合kubernetes的资源配额机制，限定不同租户能占用的资源，例如CPU使用量、内存使用量等等，来实现租户可用资源的管理。
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kubernetes在集群启动之后，会默认创建几个namespace
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```bash
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[root@master ~]# kubectl get namespace
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NAME STATUS AGE
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default Active 28d # 所有未指定Namespace的对象都会被分配在default命名空间
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kube-flannel Active 28d
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kube-node-lease Active 28d # 集群节点之间的心跳维护，v1.13开始引入
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kube-public Active 28d # 此命名空间下的资源可以被所有人访问（包括未认证用户）
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kube-system Active 28d # 所有由Kubernetes系统创建的资源都处于这个命名空间
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```
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下面来看namespace资源的具体操作：
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**查看**
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```bash
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# 1 查看所有的ns 命令：kubectl get ns
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[root@master ~]# kubectl get ns
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NAME STATUS AGE
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default Active 28d
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kube-flannel Active 28d
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kube-node-lease Active 28d
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kube-public Active 28d
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kube-system Active 28d
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# 2 查看指定的ns 命令：kubectl get ns ns名称
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[root@master ~]# kubectl get ns default
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NAME STATUS AGE
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default Active 28d
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# 3 指定输出格式 命令：kubectl get ns ns名称 -o 格式参数
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# kubernetes支持的格式有很多，比较常见的是wide、json、yaml
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[root@master ~]# kubectl get ns default -o yaml
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apiVersion: v1
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kind: Namespace
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metadata:
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creationTimestamp: "2025-04-14T12:21:54Z"
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labels:
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kubernetes.io/metadata.name: default
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name: default
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resourceVersion: "191"
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uid: dd556322-ffcd-4a72-a8df-8723090e82c0
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spec:
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finalizers:
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- kubernetes
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status:
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phase: Active
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# 4 查看ns详情 命令：kubectl describe ns ns名称
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[root@master ~]# kubectl describe ns default
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Name: default
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Labels: kubernetes.io/metadata.name=default
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Annotations: <none>
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Status: Active
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# ResourceQuota 针对namespace做的资源限制
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# LimitRange针对namespace中的每个组件做的资源限制
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No resource quota.
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No LimitRange resource.
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```
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**创建**
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```bash
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# 创建namespace
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[root@master ~]# kubectl create ns dev
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namespace/dev created
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```
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**删除**
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```bash
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# 删除namespace
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[root@master ~]# kubectl delete ns dev
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namespace "dev" deleted
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```
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**配置方式**
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首先准备一个yaml文件：ns-dev.yaml
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```yaml
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apiVersion: v1
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kind: Namespace
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metadata:
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name: dev
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```
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然后就可以执行对应的创建和删除命令了：
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- 创建：kubectl create -f ns-dev.yaml
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- 删除：kubectl delete -f ns-dev.yaml
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## 二：Pod
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Pod是kubernetes集群进行管理的最小单元，程序要运行必须部署在容器中，而容器必须存在于Pod中。
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Pod可以认为是容器的封装，一个Pod中可以存在一个或者多个容器。
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kubernetes在集群启动之后，集群中的各个组件也都是以Pod方式运行的。可以通过下面命令查看：
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```bash
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[root@master ~]# kubectl get pod -n kube-system
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NAME READY STATUS RESTARTS AGE
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coredns-64897985d-hzb7c 1/1 Running 1 (28d ago) 28d
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coredns-64897985d-l2nvk 1/1 Running 1 (28d ago) 28d
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etcd-master 1/1 Running 1 (28d ago) 28d
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kube-apiserver-master 1/1 Running 1 (28d ago) 28d
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kube-controller-manager-master 1/1 Running 1 (28d ago) 28d
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kube-proxy-fxv98 1/1 Running 1 (28d ago) 28d
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kube-proxy-mtn5n 1/1 Running 1 (28d ago) 28d
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kube-proxy-x82nf 1/1 Running 1 (28d ago) 28d
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kube-scheduler-master 1/1 Running 1 (28d ago) 28d
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```
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**创建并运行**
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kubernetes没有提供单独运行Pod的命令，都是通过Pod控制器来实现的
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```bash
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# 命令格式： kubectl run (pod控制器名称) [参数]
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# --image 指定Pod的镜像
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# --port 指定端口
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# --namespace 指定namespace
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[root@master ~]# kubectl run nginx --image=nginx:latest --port=80 --namespace dev
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pod/nginx created
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```
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**查看pod信息**
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```bash
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# 查看Pod基本信息
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[root@master ~]# kubectl get pods -n dev
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NAME READY STATUS RESTARTS AGE
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nginx 1/1 Running 0 41s
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# 查看Pod的详细信息
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[root@master ~]# kubectl describe pod nginx -n dev
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Name: nginx
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Namespace: dev
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Priority: 0
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Node: node1/192.168.159.131
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Start Time: Tue, 13 May 2025 15:18:44 +0800
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Labels: run=nginx
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Annotations: <none>
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Status: Running
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IP: 10.244.1.2
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IPs:
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IP: 10.244.1.2
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Containers:
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nginx:
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Container ID: docker://e5ac12d1fc9534410f1716e7b5d67c827ae9c9a6eba2691e8dd7e6b0f31091da
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Image: nginx:latest
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Image ID: docker-pullable://nginx@sha256:c15da6c91de8d2f436196f3a768483ad32c258ed4e1beb3d367a27ed67253e66
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Port: 80/TCP
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Host Port: 0/TCP
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State: Running
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Started: Tue, 13 May 2025 15:19:21 +0800
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Ready: True
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Restart Count: 0
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Environment: <none>
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Mounts:
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/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-4d89h (ro)
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Conditions:
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Type Status
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Initialized True
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Ready True
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ContainersReady True
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PodScheduled True
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Volumes:
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kube-api-access-4d89h:
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Type: Projected (a volume that contains injected data from multiple sources)
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TokenExpirationSeconds: 3607
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ConfigMapName: kube-root-ca.crt
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ConfigMapOptional: <nil>
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DownwardAPI: true
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QoS Class: BestEffort
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Node-Selectors: <none>
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Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
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node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
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Events:
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Type Reason Age From Message
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---- ------ ---- ---- -------
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Normal Scheduled 46s default-scheduler Successfully assigned dev/nginx to node1
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Normal Pulling 45s kubelet Pulling image "nginx:latest"
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Normal Pulled 9s kubelet Successfully pulled image "nginx:latest" in 35.843886421s
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Normal Created 9s kubelet Created container nginx
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Normal Started 9s kubelet Started container nginx
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```
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**访问Pod**
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```bash
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# 获取podIP
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[root@master ~]# kubectl get pods -n dev -o wide
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NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
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nginx 1/1 Running 0 75s 10.244.1.2 node1 <none> <none>
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# 创建service-nodeport.yaml
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apiVersion: v1
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kind: Service
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metadata:
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name: service-nodeport
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namespace: dev
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spec:
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selector:
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app: nginx-pod
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type: NodePort
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ports:
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- port: 80
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nodePort: 30001
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targetPort: 80
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# 创建service
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[root@master ~]# kubectl create -f service-nodeport.yaml
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service/service-nodeport created
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# 查看service
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[root@master ~]# kubectl get svc -n dev -o wide
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NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
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service-nodeport NodePort 10.103.76.162 <none> 80:30001/TCP 5s app=nginx-pod
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# 接下来可以通过电脑主机的浏览器去访问集群中任意一个nodeip的30002端口，即可访问到pod
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```
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**删除指定Pod**
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```bash
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# 删除指定Pod
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[root@master ~]# kubectl delete pod nginx -n dev
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pod "nginx" deleted
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```
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**配置操作**
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创建一个pod-nginx.yaml，内容如下：
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```yaml
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apiVersion: v1
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kind: Pod
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metadata:
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name: nginx
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namespace: dev
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spec:
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containers:
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- image: nginx:latest
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name: pod
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ports:
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- name: nginx-port
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containerPort: 80
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protocol: TCP
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```
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然后就可以执行对应的创建和删除命令了：
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- 创建：kubectl create -f pod-nginx.yaml
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- 删除：kubectl delete -f pod-nginx.yaml
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## 三：Label
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Label是kubernetes系统中的一个重要概念。它的作用就是在资源上添加标识，用来对它们进行区分和选择。
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Label的特点：
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- 一个Label会以key/value键值对的形式附加到各种对象上，如Node、Pod、Service等等
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- 一个资源对象可以定义任意数量的Label ，同一个Label也可以被添加到任意数量的资源对象上去
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- Label通常在资源对象定义时确定，当然也可以在对象创建后动态添加或者删除
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可以通过Label实现资源的多维度分组，以便灵活、方便地进行资源分配、调度、配置、部署等管理工作。
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一些常用的Label 示例如下：
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- 版本标签："version":"release", "version":"stable"…
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- 环境标签："environment":"dev"，"environment":"test"，"environment":"pro"
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- 架构标签："tier":"frontend"，"tier":"backend"
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标签定义完毕之后，还要考虑到标签的选择，这就要使用到Label Selector，即：
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Label用于给某个资源对象定义标识
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Label Selector用于查询和筛选拥有某些标签的资源对象
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当前有两种Label Selector：
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- 基于等式的Label Selector
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name = slave: 选择所有包含Label中key="name"且value="slave"的对象
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env != production: 选择所有包括Label中的key="env"且value不等于"production"的对象
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- 基于集合的Label Selector
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name in (master, slave): 选择所有包含Label中的key="name"且value="master"或"slave"的对象
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name not in (frontend): 选择所有包含Label中的key="name"且value不等于"frontend"的对象
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标签的选择条件可以使用多个，此时将多个Label Selector进行组合，使用逗号","进行分隔即可。例如：
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- name=slave，env!=production
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- name not in (frontend)，env!=production
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**命令方式**
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```bash
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# 为pod资源打标签
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[root@master ~]# kubectl label pod nginx version=1.0 -n dev
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pod/nginx labeled
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# 查看标签
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[root@master ~]# kubectl get pod nginx -n dev --show-labels
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NAME READY STATUS RESTARTS AGE LABELS
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nginx 1/1 Running 0 113s version=1.0
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# 为pod资源更新标签
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[root@master ~]# kubectl label pod nginx version=2.0 -n dev --overwrite
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pod/nginx labeled
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# 查看标签
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[root@master ~]# kubectl get pod nginx -n dev --show-labels
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NAME READY STATUS RESTARTS AGE LABELS
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nginx 1/1 Running 0 2m53s version=2.0
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# 筛选标签
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[root@master ~]# kubectl get pod -n dev -l version=2.0 --show-labels
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NAME READY STATUS RESTARTS AGE LABELS
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nginx 1/1 Running 0 3m17s version=2.0
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[root@master ~]# kubectl get pod -n dev -l version!=2.0 --show-labels
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No resources found in dev namespace.
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# 删除标签
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[root@master ~]# kubectl label pod nginx -n dev version-
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pod/nginx unlabeled
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```
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**配置方式**
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```yaml
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apiVersion: v1
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kind: Pod
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metadata:
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name: nginx
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namespace: dev
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labels:
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version: "3.0"
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env: "test"
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spec:
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containers:
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- image: nginx:latest
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name: pod
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ports:
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- name: nginx-port
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containerPort: 80
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protocol: TCP
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```
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然后就可以执行对应的更新命令了：kubectl apply -f pod-nginx.yaml
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## 四：Deployment
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在kubernetes中，Pod是最小的控制单元，但是kubernetes很少直接控制Pod，一般都是通过Pod控制器来完成的。Pod控制器用于pod的管理，确保pod资源符合预期的状态，当pod的资源出现故障时，会尝试进行重启或重建pod。
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在kubernetes中Pod控制器的种类有很多，本章节只介绍一种：Deployment。
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**命令操作**
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```bash
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# 命令格式: kubectl create deployment 名称 [参数]
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# --image 指定pod的镜像
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# --port 指定端口
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# --replicas 指定创建pod数量
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# --namespace 指定namespace
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[root@master ~]# kubectl create deployment nginx --image=nginx:latest --replicas=3 -n dev
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deployment.apps/nginx create
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# 查看创建的Pod
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[root@master ~]# kubectl get pods -n dev
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NAME READY STATUS RESTARTS AGE
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nginx-7c658794b9-2w5gx 1/1 Running 0 71s
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nginx-7c658794b9-4b7cs 1/1 Running 0 71s
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nginx-7c658794b9-k9bh7 1/1 Running 0 71s
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# 查看deployment的信息
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[root@master ~]# kubectl get deploy -n dev
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NAME READY UP-TO-DATE AVAILABLE AGE
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nginx 3/3 3 3 96s
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# UP-TO-DATE：成功升级的副本数量
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# AVAILABLE：可用副本的数量
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[root@master ~]# kubectl get deploy -n dev -o wide
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NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR
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nginx 3/3 3 3 2m1s nginx nginx:latest app=nginx
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# 查看deployment的详细信息
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[root@master ~]# kubectl describe deploy nginx -n dev
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Name: nginx
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Namespace: dev
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CreationTimestamp: Thu, 15 May 2025 15:48:56 +0800
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Labels: app=nginx
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Annotations: deployment.kubernetes.io/revision: 1
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Selector: app=nginx
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Replicas: 3 desired | 3 updated | 3 total | 3 available | 0 unavailable
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StrategyType: RollingUpdate
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MinReadySeconds: 0
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RollingUpdateStrategy: 25% max unavailable, 25% max surge
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Pod Template:
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Labels: app=nginx
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Containers:
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nginx:
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Image: nginx:latest
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Port: <none>
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Host Port: <none>
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Environment: <none>
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Mounts: <none>
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Volumes: <none>
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Conditions:
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Type Status Reason
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---- ------ ------
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Available True MinimumReplicasAvailable
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Progressing True NewReplicaSetAvailable
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OldReplicaSets: <none>
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NewReplicaSet: nginx-7c658794b9 (3/3 replicas created)
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Events:
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Type Reason Age From Message
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---- ------ ---- ---- -------
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Normal ScalingReplicaSet 2m25s deployment-controller Scaled up replica set nginx-7c658794b9 to 3
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# 删除
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[root@master ~]# kubectl delete deploy nginx -n dev
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deployment.apps "nginx" deleted
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```
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**配置操作**
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创建一个deploy-nginx.yaml，内容如下：
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```yaml
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apiVersion: apps/v1
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kind: Deployment
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metadata:
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name: nginx
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namespace: dev
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spec:
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replicas: 3
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selector:
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matchLabels:
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run: nginx
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template:
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metadata:
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||
labels:
|
||
run: nginx
|
||
spec:
|
||
containers:
|
||
- image: nginx:latest
|
||
name: nginx
|
||
ports:
|
||
- containerPort: 80
|
||
protocol: TCP
|
||
```
|
||
|
||
然后就可以执行对应的创建和删除命令了：
|
||
|
||
- 创建：kubectl create -f deploy-nginx.yaml
|
||
- 删除：kubectl delete -f deploy-nginx.yaml
|
||
|
||
## 五：Service
|
||
|
||
通过上节课的学习，已经能够利用Deployment来创建一组Pod来提供具有高可用性的服务。
|
||
|
||
虽然每个Pod都会分配一个单独的Pod IP，然而却存在如下两问题：
|
||
|
||
- Pod IP 会随着Pod的重建产生变化
|
||
- Pod IP 仅仅是集群内可见的虚拟IP，外部无法访问
|
||
|
||
这样对于访问这个服务带来了难度。因此，kubernetes设计了Service来解决这个问题。
|
||
|
||
Service可以看作是一组同类Pod对外的访问接口。借助Service，应用可以方便地实现服务发现和负载均衡。
|
||
|
||
|
||
|
||
**创建集群内部可访问的Service**
|
||
|
||
```bash
|
||
# 暴露Service
|
||
[root@master ~]# kubectl expose deploy nginx --name=svc-nginx1 --type=ClusterIP --port=80 --target-port=80 -n dev
|
||
service/svc-nginx1 exposed
|
||
|
||
# 查看service
|
||
[root@master ~]# kubectl get svc svc-nginx1 -n dev -o wide
|
||
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
|
||
svc-nginx1 ClusterIP 10.99.146.46 <none> 80/TCP 46s app=nginx
|
||
|
||
# 这里产生了一个CLUSTER-IP，这就是service的IP，在Service的生命周期中，这个地址是不会变动的
|
||
# 可以通过这个IP访问当前service对应的POD
|
||
[root@master ~]# curl 10.99.146.46:80
|
||
<!DOCTYPE html>
|
||
<html>
|
||
<head>
|
||
<title>Welcome to nginx!</title>
|
||
<style>
|
||
html { color-scheme: light dark; }
|
||
body { width: 35em; margin: 0 auto;
|
||
font-family: Tahoma, Verdana, Arial, sans-serif; }
|
||
</style>
|
||
</head>
|
||
<body>
|
||
<h1>Welcome to nginx!</h1>
|
||
<p>If you see this page, the nginx web server is successfully installed and
|
||
working. Further configuration is required.</p>
|
||
|
||
<p>For online documentation and support please refer to
|
||
<a href="http://nginx.org/">nginx.org</a>.<br/>
|
||
Commercial support is available at
|
||
<a href="http://nginx.com/">nginx.com</a>.</p>
|
||
|
||
<p><em>Thank you for using nginx.</em></p>
|
||
</body>
|
||
</html>
|
||
```
|
||
|
||
**创建集群外部也可访问的Service**
|
||
|
||
```bash
|
||
# 上面创建的Service的type类型为ClusterIP，这个ip地址只用集群内部可访问
|
||
# 如果需要创建外部也可以访问的Service，需要修改type为NodePort
|
||
[root@master ~]# kubectl expose deploy nginx --name=svc-nginx2 --type=NodePort --port=80 --target-port=80 -n dev
|
||
service/svc-nginx2 exposed
|
||
|
||
# 此时查看，会发现出现了NodePort类型的Service，而且有一对Port（80:31928/TC）
|
||
[root@master ~]# kubectl get svc svc-nginx2 -n dev -o wide
|
||
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
|
||
svc-nginx2 NodePort 10.111.36.221 <none> 80:32259/TCP 14s app=nginx
|
||
|
||
# 接下来就可以通过集群外的主机访问 节点IP:31928访问服务了
|
||
# 例如在的电脑主机上通过浏览器访问下面的地址
|
||
http://192.168.159.130:32259
|
||
```
|
||
|
||
|
||
|
||
**删除Service**
|
||
|
||
```bash
|
||
[root@master ~]# kubectl delete svc svc-nginx1 -n dev
|
||
service "svc-nginx1" deleted
|
||
```
|
||
|
||
**配置方式**
|
||
|
||
创建一个svc-nginx.yaml，内容如下：
|
||
|
||
```yaml
|
||
apiVersion: v1
|
||
kind: Service
|
||
metadata:
|
||
name: svc-nginx
|
||
namespace: dev
|
||
spec:
|
||
clusterIP: 10.109.179.231 #固定svc的内网ip
|
||
ports:
|
||
- port: 80
|
||
protocol: TCP
|
||
targetPort: 80
|
||
selector:
|
||
run: nginx
|
||
type: ClusterIP
|
||
```
|
||
|
||
然后就可以执行对应的创建和删除命令了：
|
||
|
||
- 创建：kubectl create -f svc-nginx.yaml
|
||
- 删除：kubectl delete -f svc-nginx.yaml
|
||
|
||
**小结**
|
||
|
||
至此，已经掌握了Namespace、Pod、Deployment、Service资源的基本操作，有了这些操作，就可以在kubernetes集群中实现一个服务的简单部署和访问了，但是如果想要更好的使用kubernetes，就需要深入学习这几种资源的细节和原理。 |