k8s之hello-world

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环境：CentOs 7.2

一、使用k8s搭建hello-world,安装kubernetes
1.关闭CentOS自带的防火墙

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systemctl disable firewalld
systemctl stop firewalld

2.安装etcd和kubernetes

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yum install -y etcd kubernetes

3.修改配置文件/etc/sysconfig/docker和/etc/kubernetes/apiserver为如下。

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/etc/sysconfig/docker/

OPTIONS='--selinux-enabled=false --log-driver=journald --signature-verification=false'

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# 将--admission-control参数中的ServiceAccount删除
/etc/kubernetes/apiserver
KUBE_ADMISSION_CONTROL="--admission-control=NamespaceLifecycle,NamespaceExists,LimitRanger,SecurityContextDeny,ResourceQuota"

4.按如下顺序启动所有的服务

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systemctl start etcd
systemctl start docker
systemctl start kube-apiserver
systemctl start kube-controller-manager
systemctl start kube-scheduler
systemctl start kubelet
systemctl start kube-proxy

二、搭建hello-world案例
image
1.拉取镜像

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docker pull kubeguide/guestbook-php-frontend  # php web服务
docker pull kubeguide/redis-master
docker pull kubeguide/guestbook-redis-slave

  1. 创建redis-master Pod和服务

  • 为redis-master服务创建名为redis-master的RC定义文件：redis-master-controller.yaml

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    apiVersion: v1
    kind: ReplicationController
    metadata:
      name: redis-master
      labels:
        name: redis-master
    spec:
      replicas: 1
      selector:
        name: redis-master
      template:
        metadata:
          labels:
            name: redis-master
        spec:
          containers:
          - name: master
            image: kubeguide/redis-master
            ports:
            - containerPort: 6379

  • 发布到集群中
    kubectl create -f redis-master-controller.yaml

  • 创建与之关联的Service,编辑文件redis-master-service.yaml

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    apiVersion: v1
    kind: Service
    metadata:
      name: redis-master
      labels:
        name: redis-master
    spec:
      ports:
      - port: 6379
        targetPort: 6379
      selector:
        name: redis-master

  • 发布Service
    kubectl create -f redis-master-service.yaml

3.创建redis-slave Pod和服务

  • 创建Pod
    vim redis-slave-controller.yaml

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    apiVersion: v1
    kind: ReplicationController
    metadata:
      name: redis-slave
      labels:
        name: redis-slave
    spec:
      replicas: 2
      selector:
        name: redis-slave
      template:
        metadata:
          labels:
            name: redis-slave
        spec:
          containers:
          - name: slave
            image: kubeguide/guestbook-redis-slave
            env:
            - name: GET_HOSTS_FROM
              value: env
            ports:
            - containerPort: 6379

  • 发布Pod到集群
    kubectl create -f redis-slave-controller.yaml

  • 创建Service
    vim redis-slave-service.yaml

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    apiVersion: v1
    kind: Service
    metadata:
      name: redis-slave
      labels:
        name: redis-slave
    spec:
      ports:
      - port: 6379
      selector:
        name: redis-slave

  • 发布服务
    kubectl create -f redis-slave-service.yaml

4.创建frontend Pod和服务

  • 创建Pod
    vim frontend-controller.yaml

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    apiVersion: v1
    kind: ReplicationController
    metadata:
      name: frontend
      labels:
        name: frontend
    spec:
      replicas: 3
      selector:
        name: frontend
      template:
        metadata:
          labels:
            name: frontend
        spec:
          containers:
            - name: frontend
              image: kubeguide/guestbook-php-frontend
              env:
                - name: GET_HOSTS_FROM
                  value: env
              ports:
                - containerPort: 80

  • 发布Pod到集群
    kubectl create -f frontend-controller.yaml

  • 创建服务
    vim frontend-service.yaml

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    apiVersion: v1
    kind: Service
    metadata:
      name: frontend
      labels:
        name: frontend
    spec:
      type: NodePort
      ports:
        - port: 80
          nodePort: 30001
      selector:
        name: frontend

  • 发布Service
    kubectl create -f frontend-service.yaml

5.查看Pod和服务状态
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集群中其它Pod如何访问redis-master中的服务？
redis-master服务被分配了一个值为10.254.187.40的虚拟IP,kubernetes集群中的其它Pod就可以通过这个IP访问redis-master服务。由于IP地址是在服务创建后由kebernetes系统自动分配的,其它Pod中无法预先知道某个Service的虚拟IP,为此kuberntes通过使用环境变量来实现服务发现,在每个Pod的容器里都增加了一组Service相关的环境变量,用来记录从服务名到虚拟IP地址的映射关系。
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image

5.通过浏览器访问网页,输入URL: http://虚拟机IP:30001
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在创建过程中可能会用到的命令

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kubectl get pods    #查看pod状态
kubectl get rc      #查看RC
kubectl get service #查看服务

kubectl logs [pod-name]   # 查看日志
kubectl delete pods [pod-name]  #删除pod
kubectl delete rc [rc-name]          #删除rc
kubectl delete service [service-name]   #删除服务

所遇问题：
1.docker启动失败,提示Error starting daemon: SELinux is not supported with the overlay2 graph driver on this kernel. Either boot into a newer kernel or disable selinux in docker (—selinux-enabled=false)

vim /etc/sysconfig/docker

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OPTIONS='--selinux-enabled --log-driver=journald --signature-verification=false'

改为

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OPTIONS='--selinux-enabled=false --log-driver=journald --signature-verification=false'

2.创建pod一直处于ContainerCreating状态,原因是不能拉取pod的基础镜像,[https://blog.csdn.net/weixin_34054866/article/details/87525597]

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yum install -y *rhsm*
 
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/python-rhsm-certificates-1.19.10-1.el7_4.x86_64.rpm
 
rpm2cpio python-rhsm-certificates-1.19.10-1.el7_4.x86_64.rpm | cpio -iv --to-stdout ./etc/rhsm/ca/redhat-uep.pem | tee /etc/rhsm/ca/redhat-uep.pem

3.启动frontend pod时报错, AH00534: apache2: Configuration error: No MPM loaded

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systemctl stop docker              //停掉docker服务
rm -rf /var/lib/docker             //注意会清掉docker images的镜像,需重新拉取镜像
vi /etc/sysconfig/docker-storage   //将文件里的overlay2改成devicemapper即可
DOCKER_STORAGE_OPTIONS="--storage-driver overlay2 "  #修改前
DOCKER_STORAGE_OPTIONS="--storage-driver devicemapper "   #修改后

重启docker服务
systemctl start docker

Ref：
1.kubernetes权威指南
2.https://blog.csdn.net/a1010256340/article/details/80106156
3.https://blog.csdn.net/weixin_34054866/article/details/87525597
4.https://www.cnblogs.com/guyeshanrenshiwoshifu/p/9147238.html