關於K8S：
Kubernetes是Google開源的容器集羣管理系統。它構建於docker技術之上，爲容器化的應用提供資源調度、部署運行、服務發現、擴 容縮容等整一套功能，本質上可看作是基於容器技術的mini-PaaS平臺。
相信看過我博客的童鞋應該知道，我在14年的時候就發表了一篇名爲Docker容器管理之Kubernetes當時國內Docker剛剛興起，對於Docker的興起我很有感觸，彷彿一瞬間就火了，當時也是一個偶然的機會瞭解到K8S，所以當時就寫文簡單的介紹了下K8S以及如何採用源碼部署。今時不同往日K8S在容器界已經是翹首，再讀舊文有感而發，索性來研究下kubeadm安裝K8S以及Dashboard功能預覽。
環境描述：
採用CentOS7.4 minimual，docker 1.13，kubeadm 1.10.0，etcd 3.0， k8s 1.10.0
我們這裏選用三個節點搭建一個實驗環境。
10.0.100.202 k8smaster
10.0.100.203 k8snode1
10.0.100.204 k8snode2
準備環境：
1.配置好各節點hosts文件
2.關閉各節點系統防火牆
3.關閉各節點SElinux
4.關閉各節點swap
5.配置各節點系統內核參數使流過網橋的流量也進入iptables/netfilter框架中，在/etc/sysctl.conf中添加以下配置：
net.bridge.bridge-nf-call-iptables = 1 net.bridge.bridge-nf-call-ip6tables = 1 sysctl -p
使用kubeadm安裝：
1.首先配置各節點阿里K8S YUM源
cat <<EOF > /etc/yum.repos.d/kubernetes.repo [kubernetes] name=Kubernetes baseurl=https://mirrors.aliyun.com/kubernetes/yum/repos/kubernetes-el7-x86_64 enabled=1 gpgcheck=0 EOF yum -y install epel-release yum clean all yum makecache
2.在各節點安裝kubeadm和相關工具包
yum -y install docker kubelet kubeadm kubectl kubernetes-cni
3.啓動Docker與kubelet服務
systemctl enable docker && systemctl start docker systemctl enable kubelet && systemctl start kubelet
提示：此時kubelet的服務運行狀態是異常的，因爲缺少主配置文件kubelet.conf。但可以暫不處理，因爲在完成Master節點的初始化後纔會生成這個配置文件。
4.下載K8S相關鏡像（Master節點操作）
因爲無法直接訪問gcr.io下載鏡像，所以需要配置一個國內的容器鏡像加速器
配置一個阿里雲的加速器：
登錄 https://cr.console.aliyun.com/
在頁面中找到並點擊鏡像加速按鈕，即可看到屬於自己的專屬加速鏈接，選擇Centos版本後即可看到配置方法。
提示：在阿里雲上使用 Docker 並配置阿里雲鏡像加速器，可能會遇到 daemon.json 導致 docker daemon 無法啓動的問題，可以通過以下方法解決。
你需要的是編輯 vim /etc/sysconfig/docker 然後 OPTIONS='--selinux-enabled --log-driver=journald --registry-mirror=http://xxxx.mirror.aliyuncs.com' registry-mirror 輸入你的鏡像地址 最後 service docker restart 重啓 daemon 然後 ps aux | grep docker 然後你就會發現帶有鏡像的啓動參數了。
5.下載K8S相關鏡像
OK，解決完加速器的問題之後，開始下載k8s相關鏡像，下載後將鏡像名改爲k8s.gcr.io/開頭的名字，以便kubeadm識別使用。
#!/bin/bash
images=(kube-proxy-amd64:v1.10.0 kube-scheduler-amd64:v1.10.0 kube-controller-manager-amd64:v1.10.0 kube-apiserver-amd64:v1.10.0
etcd-amd64:3.1.12 pause-amd64:3.1 kubernetes-dashboard-amd64:v1.8.3 k8s-dns-sidecar-amd64:1.14.8 k8s-dns-kube-dns-amd64:1.14.8
k8s-dns-dnsmasq-nanny-amd64:1.14.8)
for imageName in ${images[@]} ; do
docker pull keveon/$imageName
docker tag keveon/$imageName k8s.gcr.io/$imageName
docker rmi keveon/$imageName
done上面的shell腳本主要做了3件事，下載各種需要用到的容器鏡像、重新打標記爲符合k8s命令規範的版本名稱、清除舊的容器鏡像。
提示：鏡像版本一定要和kubeadm安裝的版本一致，否則會出現time out問題。
6.初始化安裝K8S Master
執行上述shell腳本，等待下載完成後，執行kubeadm init
[root@k8smaster ~]# kubeadm init --kubernetes-version=v1.10.0 --pod-network-cidr=10.244.0.0/16 [init] Using Kubernetes version: v1.10.0 [init] Using Authorization modes: [Node RBAC] [preflight] Running pre-flight checks. [WARNING Service-Kubelet]: kubelet service is not enabled, please run 'systemctl enable kubelet.service' [WARNING FileExisting-crictl]: crictl not found in system path Suggestion: go get github.com/kubernetes-incubator/cri-tools/cmd/crictl [preflight] Starting the kubelet service [certificates] Generated ca certificate and key. [certificates] Generated apiserver certificate and key. [certificates] apiserver serving cert is signed for DNS names [k8smaster kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 10.0.100.202] [certificates] Generated apiserver-kubelet-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 [localhost] and IPs [127.0.0.1] [certificates] Generated etcd/peer certificate and key. [certificates] etcd/peer serving cert is signed for DNS names [k8smaster] and IPs [10.0.100.202] [certificates] Generated etcd/healthcheck-client certificate and key. [certificates] Generated apiserver-etcd-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] 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 21.001790 seconds [uploadconfig] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace [markmaster] Will mark node k8smaster as master by adding a label and a taint [markmaster] Master k8smaster tainted and labelled with key/value: node-role.kubernetes.io/master="" [bootstraptoken] Using token: thczis.64adx0imeuhu23xv [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: kube-dns [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 10.0.100.202:6443 --token thczis.64adx0imeuhu23xv --discovery-token-ca-cert-hash sha256:fa7b11bb569493fd44554aab0afe55a4c051cccc492dbdfafae6efeb6ffa80e6
提示：選項--kubernetes-version=v1.10.0是必須的，否則會因爲訪問google網站被牆而無法執行命令。這裏使用v1.10.0版本，剛纔前面也說到了下載的容器鏡像版本必須與K8S版本一致否則會出現time out。
上面的命令大約需要1分鐘的過程，期間可以觀察下tail -f /var/log/message日誌文件的輸出，掌握該配置過程和進度。上面最後一段的輸出信息保存一份，後續添加工作節點還要用到。
7.配置kubectl認證信息（Master節點操作）
# 對於非root用戶 mkdir -p $HOME/.kube sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config sudo chown $(id -u):$(id -g) $HOME/.kube/config # 對於root用戶 export KUBECONFIG=/etc/kubernetes/admin.conf 也可以直接放到~/.bash_profile echo "export KUBECONFIG=/etc/kubernetes/admin.conf" >> ~/.bash_profile
8.安裝flannel網絡（Master節點操作）
mkdir -p /etc/cni/net.d/
cat <<EOF> /etc/cni/net.d/10-flannel.conf
{
“name”: “cbr0”,
“type”: “flannel”,
“delegate”: {
“isDefaultGateway”: true
}
}
EOF
mkdir /usr/share/oci-umount/oci-umount.d -p
mkdir /run/flannel/
cat <<EOF> /run/flannel/subnet.env
FLANNEL_NETWORK=10.244.0.0/16
FLANNEL_SUBNET=10.244.1.0/24
FLANNEL_MTU=1450
FLANNEL_IPMASQ=true
EOF
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/v0.9.1/Documentation/kube-flannel.yml9.讓node1、node2加入集羣
在node1和node2節點上分別執行kubeadm join命令，加入集羣：
[root@k8snode1 ~]# kubeadm join 10.0.100.202:6443 --token thczis.64adx0imeuhu23xv --discovery-token-ca-cert-hash sha256:fa7b11bb569493fd44554aab0afe55a4c051cccc492dbdfafae6efeb6ffa80e6 [preflight] Running pre-flight checks. [WARNING Service-Kubelet]: kubelet service is not enabled, please run 'systemctl enable kubelet.service' [WARNING FileExisting-crictl]: crictl not found in system path Suggestion: go get github.com/kubernetes-incubator/cri-tools/cmd/crictl [discovery] Trying to connect to API Server "10.0.100.202:6443" [discovery] Created cluster-info discovery client, requesting info from "https://10.0.100.202:6443" [discovery] Requesting info from "https://10.0.100.202:6443" 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 "10.0.100.202:6443" [discovery] Successfully established connection with API Server "10.0.100.202:6443" 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 node join the cluster.
提示：細心的童鞋應該會發現，這段命令其實就是前面K8S Matser安裝成功後我讓你們保存的那段命令。
默認情況下，Master節點不參與工作負載，但如果希望安裝出一個All-In-One的k8s環境，則可以執行以下命令，讓Master節點也成爲一個Node節點：
kubectl taint nodes --all node-role.kubernetes.io/master-
10.驗證K8S Master是否搭建成功（Master節點操作）
# 查看節點狀態 kubectl get nodes # 查看pods狀態 kubectl get pods --all-namespaces # 查看K8S集羣狀態 kubectl get cs
常見錯誤解析
安裝時候最常見的就是time out，因爲K8S鏡像在國外，所以我們在前面就說到了提前把他下載下來，可以用一個國外機器採用habor搭建一個私有倉庫把鏡像都download下來。
[root@k8smaster ~]# kubeadm init [init] Using Kubernetes version: v1.10.0 [init] Using Authorization modes: [Node RBAC] [preflight] Running pre-flight checks. [WARNING Service-Kubelet]: kubelet service is not enabled, please run 'systemctl enable kubelet.service' [WARNING FileExisting-crictl]: crictl not found in system path Suggestion: go get github.com/kubernetes-incubator/cri-tools/cmd/crictl [preflight] Starting the kubelet service [certificates] Generated ca certificate and key. [certificates] Generated apiserver certificate and key. [certificates] apiserver serving cert is signed for DNS names [k8smaster kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 10.0.100.202] [certificates] Generated apiserver-kubelet-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 [localhost] and IPs [127.0.0.1] [certificates] Generated etcd/peer certificate and key. [certificates] etcd/peer serving cert is signed for DNS names [k8smaster] and IPs [10.0.100.202] [certificates] Generated etcd/healthcheck-client certificate and key. [certificates] Generated apiserver-etcd-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] 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. Unfortunately, an error has occurred: timed out waiting for the condition This error is likely caused by: - The kubelet is not running - The kubelet is unhealthy due to a misconfiguration of the node in some way (required cgroups disabled) - Either there is no internet connection, or imagePullPolicy is set to "Never", so the kubelet cannot pull or find the following control plane images: - k8s.gcr.io/kube-apiserver-amd64:v1.10.0 - k8s.gcr.io/kube-controller-manager-amd64:v1.10.0 - k8s.gcr.io/kube-scheduler-amd64:v1.10.0 - k8s.gcr.io/etcd-amd64:3.1.12 (only if no external etcd endpoints are configured) If you are on a systemd-powered system, you can try to troubleshoot the error with the following commands: - 'systemctl status kubelet' - 'journalctl -xeu kubelet' couldn't initialize a Kubernetes cluster
那出現這個問題大部分原因是因爲安裝的K8S版本和依賴的K8S相關鏡像版本不符導致的，關於這部分排錯可以查看/var/log/message我們在文章開始安裝的時候也提到了要多看日誌。
還有些童鞋可能會說，那我安裝失敗了，怎麼清理環境重新安裝啊？下面教大家一條命令：
kubeadm reset
好了，至此就完成了K8S三節點集羣的安裝部署。