本文主要介绍通过Play with Kubernetes来搭建5个节点的Kubernetes集群，其中包括一个master节点以及4个工作节点，来带领大家进入Kubernetes的世界。本文不会专注于讲解Kubernetes的高深原理也不是讲Kuberentes的具体用法，而是通过Play with Kubernetes带大家上手Kubernetes，相当于Kubernetes世界的“Hello World”！大家只需要一台可以上网的电脑以及下载装好浏览器，推荐使用google浏览器，然后需要注册Github账号或者Google账号用以登陆，然后即可上手。
1. 资源限制
- 利用内置的kubeadm来搭建Kubenetes集群，目前kube版本是v1.11.3
- 每个实例配置的资源是1 core，4G Memory，并且一次性最多只能创建5个实例，如果再创建的话，就是有以下提示：
Max instances reached
Maximum number of instances reached
- 每个集群的使用时间是4个小时（当然你可以同时启动多个集群，根据浏览器的session来判断集群）
- 在Kubernetes集群中创建的服务无法通过外网访问，只能在Play with Kubernetes的网络内访问
2. 创建Kubernetes集群
2.1 登陆
点击Play with Kubernetes地址，打开网页。点击login，登陆方式有两种：
- Github账户登陆，有github账户，即可登陆，没有的去GitHub创建一个账号
- Docker登陆，需要有google账户，即可登陆
然后点击start即可开始你的Kubernetes之旅！登陆页面为：
2.2 创建master节点
- 点击create instance创建一个新的实例，然后运行命令，初始化master节点：
[node1 ~]$ kubeadm init --apiserver-advertise-address $(hostname -i)
Initializing machine ID from random generator.
[init] using Kubernetes version: v1.11.10
[preflight] running pre-flight checks
[WARNING Service-Docker]: docker service is not active, please run 'systemctl start docker.service'
[WARNING FileContent--proc-sys-net-bridge-bridge-nf-call-iptables]: /proc/sys/net/bridge/bridge-nf-call-iptables does not exist
I1026 08:51:17.842390 800 kernel_validator.go:81] Validating kernel version
I1026 08:51:17.842768 800 kernel_validator.go:96] Validating kernel config
[preflight] The system verification failed. Printing the output from the verification:
KERNEL_VERSION: 4.4.0-165-generic
DOCKER_VERSION: 18.06.1-ce
OS: Linux
CGROUPS_CPU: enabled
CGROUPS_CPUACCT: enabled
CGROUPS_CPUSET: enabled
CGROUPS_DEVICES: enabled
CGROUPS_FREEZER: enabled
CGROUPS_MEMORY: enabled
[WARNING SystemVerification]: docker version is greater than the most recently validated version. Docker version: 18.06.1-ce. Max validated version: 17.03
[WARNING SystemVerification]: failed to parse kernel config: unable to load kernel module "configs": output - "", err - exit status 1
[preflight/images] Pulling images required for setting up a Kubernetes cluster
[preflight/images] This might take a minute or two, depending on the speed of your internet connection
[preflight/images] You can also perform this action in beforehand using 'kubeadm config images pull'
[kubelet] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[preflight] Activating the kubelet service
[certificates] Generated ca certificate and key.
[certificates] Generated apiserver certificate and key.
[certificates] apiserver serving cert is signed for DNS names [node1 kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 192.168.0.23]
[certificates] Generated apiserver-kubelet-client certificate and key.
[certificates] Generated sa key and public key.
[certificates] Generated front-proxy-ca certificate and key.
[certificates] Generated front-proxy-client certificate and key.
[certificates] Generated etcd/ca certificate and key.
[certificates] Generated etcd/server certificate and key.
[certificates] etcd/server serving cert is signed for DNS names [node1 localhost] and IPs [127.0.0.1 ::1]
[certificates] Generated etcd/peer certificate and key.
[certificates] etcd/peer serving cert is signed for DNS names [node1 localhost] and IPs [192.168.0.23 127.0.0.1 ::1]
[certificates] Generated etcd/healthcheck-client certificate and key.
[certificates] Generated apiserver-etcd-client certificate and key.
[certificates] valid certificates and keys now exist in "/etc/kubernetes/pki"
[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/admin.conf"
[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/kubelet.conf"
[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/controller-manager.conf"
[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/scheduler.conf"
[controlplane] wrote Static Pod manifest for component kube-apiserver to "/etc/kubernetes/manifests/kube-apiserver.yaml"
[controlplane] wrote Static Pod manifest for component kube-controller-manager to "/etc/kubernetes/manifests/kube-controller-manager.yaml"
[controlplane] wrote Static Pod manifest for component kube-scheduler to "/etc/kubernetes/manifests/kube-scheduler.yaml"
[etcd] Wrote Static Pod manifest for a local etcd instance to "/etc/kubernetes/manifests/etcd.yaml"
[init] waiting for the kubelet to boot up the control plane as Static Pods from directory "/etc/kubernetes/manifests"
[init] this might take a minute or longer if the control plane images have to be pulled
[apiclient] All control plane components are healthy after 50.502361 seconds
[uploadconfig] storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config-1.11" in namespace kube-system with the configuration for the kubelets in the cluster
[markmaster] Marking the node node1 as master by adding the label "node-role.kubernetes.io/master=''"
[markmaster] Marking the node node1 as master by adding the taints [node-role.kubernetes.io/master:NoSchedule]
[patchnode] Uploading the CRI Socket information "/var/run/dockershim.sock" to the Node API object "node1" asan annotation
[bootstraptoken] using token: p6wrgt.ukl5qipcf8ovg2ze
[bootstraptoken] configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials
[bootstraptoken] configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token
[bootstraptoken] configured RBAC rules to allow certificate rotation for all node client certificates in the cluster
[bootstraptoken] creating the "cluster-info" ConfigMap in the "kube-public" namespace
[addons] Applied essential addon: CoreDNS
[addons] Applied essential addon: kube-proxy
Your Kubernetes master has initialized successfully!
To start using your cluster, you need to run the following as a regular user:
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
You should now deploy a pod network to the cluster.
Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at:
https://kubernetes.io/docs/concepts/cluster-administration/addons/
You can now join any number of machines by running the following on each node
as root:
kubeadm join 192.168.0.23:6443 --token p6wrgt.ukl5qipcf8ovg2ze --discovery-token-ca-cert-hash sha256:6d431bda8393afb76b95466e2a4b0c1a712a25b25f6281cb8b9663c063a27b46
Waiting for api server to startup
Warning: kubectl apply should be used on resource created by either kubectl create --save-config or kubectl apply
daemonset.extensions/kube-proxy configured
No resources found
[node1 ~]$ kubectl apply -n kube-system -f \
> "https://cloud.we
- 初始化集群网络：
[node1 ~]$ kubectl apply -n kube-system -f \
> "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 |tr -d '\n')"
serviceaccount/weave-net created
clusterrole.rbac.authorization.k8s.io/weave-net created
clusterrolebinding.rbac.authorization.k8s.io/weave-net created
role.rbac.authorization.k8s.io/weave-net created
rolebinding.rbac.authorization.k8s.io/weave-net created
daemonset.apps/weave-net created
- 需要执行下面命令，作为一个普通用户来使用集群:
[node1 ~]$ mkdir -p $HOME/.kube
[node1 ~]$ cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
cp: '/etc/kubernetes/admin.conf' and '/root/.kube/config' are the same file
[node1 ~]$ chown $(id -u):$(id -g) $HOME/.kube/config
2.3 创建其他工作节点
- 新建一个新的实例来创建工作节点，在新的实例窗口运行：
[node3 ~]$ kubeadm join 192.168.0.23:6443 --token p6wrgt.ukl5qipcf8ovg2ze --discovery-token-ca-cert-hash sha256:6d431bda8393afb76b95466e2a4b0c1a712a25b25f6281cb8b9663c063a27b46
Initializing machine ID from random generator.
[preflight] running pre-flight checks
[WARNING RequiredIPVSKernelModulesAvailable]: error getting required builtin kernel modules: exit status 1(cut: /lib/modules/4.4.0-165-generic/modules.builtin: No such file or directory
)
[WARNING Service-Docker]: docker service is not active, please run 'systemctl start docker.service'
[WARNING FileContent--proc-sys-net-bridge-bridge-nf-call-iptables]: /proc/sys/net/bridge/bridge-nf-call-iptables does not exist
I1026 09:09:09.257504 422 kernel_validator.go:81] Validating kernel version
I1026 09:09:09.257670 422 kernel_validator.go:96] Validating kernel config
[preflight] The system verification failed. Printing the output from the verification:
KERNEL_VERSION: 4.4.0-165-generic
DOCKER_VERSION: 18.06.1-ce
OS: Linux
CGROUPS_CPU: enabled
CGROUPS_CPUACCT: enabled
CGROUPS_CPUSET: enabled
CGROUPS_DEVICES: enabled
CGROUPS_FREEZER: enabled
CGROUPS_MEMORY: enabled
[WARNING SystemVerification]: docker version is greater than the most recently validated version. Docker version: 18.06.1-ce. Max validated version: 17.03
[WARNING SystemVerification]: failed to parse kernel config: unable to load kernel module "configs": output - "", err - exit status 1
[discovery] Trying to connect to API Server "192.168.0.23:6443"
[discovery] Created cluster-info discovery client, requesting info from "https://192.168.0.23:6443"
[discovery] Requesting info from "https://192.168.0.23:6443" again to validate TLS against the pinned public key
[discovery] Cluster info signature and contents are valid and TLS certificate validates against pinned roots, will use API Server "192.168.0.23:6443"
[discovery] Successfully established connection with API Server "192.168.0.23:6443"
[kubelet] Downloading configuration for the kubelet from the "kubelet-config-1.11" ConfigMap in the kube-system namespace
[kubelet] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[preflight] Activating the kubelet service
[tlsbootstrap] Waiting for the kubelet to perform the TLS Bootstrap...
[patchnode] Uploading the CRI Socket information "/var/run/dockershim.sock" to the Node API object "node3" as an annotation
This node has joined the cluster:
* Certificate signing request was sent to master and a response
was received.
* The Kubelet was informed of the new secure connection details.
Run 'kubectl get nodes' on the master to see this n
注意：这步需根据自己matser节点终端提示进行操作，
192.168.0.23:6443只是我的master节点的ip和port，而且每个人的token以及sha密码都不一样的！
- 重复上一步，可以再创建3个工作的节点。这样加上master节点，则搭建好了一个具有5个节点的Kubernetes集群了。在master节点上运行命令，可以看到节点具体信息
[node1 ~]$ kubectl get nodes -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
node1 Ready master 1h v1.11.3 192.168.0.23 <none> CentOS Linux 7 (Core) 4.4.0-165-generic docker://18.6.1
node2 Ready <none> 57m v1.11.3 192.168.0.22 <none> CentOS Linux 7 (Core) 4.4.0-165-generic docker://18.6.1
node3 Ready <none> 54m v1.11.3 192.168.0.21 <none> CentOS Linux 7 (Core) 4.4.0-165-generic docker://18.6.1
node4 Ready <none> 53m v1.11.3 192.168.0.20 <none> CentOS Linux 7 (Core) 4.4.0-165-generic docker://18.6.1
node5 Ready <none> 46m v1.11.3 192.168.0.19 <none> CentOS Linux 7 (Core) 4.4.0-165-generic docker://18.6.1
到此，利用Play with Kubernetes搭建5个节点的K8s集群教程结束，大家可以在集群上创建自己的应用了，如pod、deployment、statefulset等。接下来会讲解如何Kubernetes一些基本概念。