摘要：部署節點節點包含的組件本文檔介紹部署一個三節點高可用集群的步驟，分別命名為安裝在每臺主機安裝。出現如下錯誤解決辦法啟動參數增加參數增加在物理機上可能并不會出現該問題。至此一個完整的高可用集群搭建完畢。

kubernetes master 節點包含的組件：

kube-apiserver

kube-scheduler

kube-controller-manager

本文檔介紹部署一個三節點高可用 master 集群的步驟，分別命名為k8s-host1、k8s-host2、k8s-host3：

k8s-host1：172.16.120.154

k8s-host2：172.16.120.155

k8s-host3：172.16.120.156

在每臺主機安裝docker。建議使用docker v1.12 , 但是 v1.11, v1.13 and 17.03 也可以正常工作. 版本 17.06+ 可能工作, 但是沒有被k8s團隊測試過。
PS：kubelet設置的cgroup driver應該和Docker設置的cgroup driver一致。這邊統一為systemd。

yum install -y docker
systemctl enable docker && systemctl start docker

cat < /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg
EOF
setenforce 0
yum install -y kubelet kubeadm kubectl
systemctl enable kubelet && systemctl start kubelet

通過運行命令setenforce 0 禁用selinux，主要為了允許容器可以訪問主機文件系統和pod networks的需要。

Some users on RHEL/CentOS 7 have reported issues with traffic being routed incorrectly due to iptables being bypassed。所以需要執行下面命令：

cat <  /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF
sysctl --system

kubeadm init --apiserver-advertise-address=172.16.120.200 --pod-network-cidr=192.168.0.0/16

apiserver-advertise-address該參數一般指定為haproxy+keepalived 的vip。

pod-network-cidr 主要是在搭建pod network（calico）時候需要在init時候指定。

出現如下錯誤：

[root@k8s-node04 ~]# kubeadm init --apiserver-advertise-address=172.16.120.200 --pod-network-cidr=192.168.0.0/16

[init] Using Kubernetes version: v1.9.0
[init] Using Authorization modes: [Node RBAC]
[preflight] Running pre-flight checks.
        [WARNING FileExisting-crictl]: crictl not found in system path
[preflight] Some fatal errors occurred:
        [ERROR Swap]: running with swap on is not supported. Please disable swap
[preflight] If you know what you are doing, you can make a check non-fatal with `--ignore-preflight-errors=...`

解決辦法：
1：kubelet啟動參數增加--fail-swap-on=false

[Service]
Environment="KUBELET_KUBECONFIG_ARGS=--bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf"
Environment="KUBELET_SYSTEM_PODS_ARGS=--pod-manifest-path=/etc/kubernetes/manifests --allow-privileged=true"
Environment="KUBELET_NETWORK_ARGS=--network-plugin=cni --cni-conf-dir=/etc/cni/net.d --cni-bin-dir=/opt/cni/bin"
Environment="KUBELET_DNS_ARGS=--cluster-dns=10.96.0.10 --cluster-domain=cluster.local"
Environment="KUBELET_AUTHZ_ARGS=--authorization-mode=Webhook --client-ca-file=/etc/kubernetes/pki/ca.crt"
Environment="KUBELET_CADVISOR_ARGS=--cadvisor-port=0"
Environment="KUBELET_CGROUP_ARGS=--cgroup-driver=systemd"
Environment="KUBELET_CERTIFICATE_ARGS=--rotate-certificates=true --cert-dir=/var/lib/kubelet/pki"
Environment="KUBELET_SWAP_ARGS=--fail-swap-on=false"
ExecStart=
ExecStart=/usr/bin/kubelet $KUBELET_KUBECONFIG_ARGS $KUBELET_SYSTEM_PODS_ARGS $KUBELET_NETWORK_ARGS $KUBELET_DNS_ARGS $KUBELET_AUTHZ_ARGS $KUBELET_CADVISOR_ARGS $KUBELET_CGROUP_ARGS $KUBELET_CERTIFICATE_ARGS $KUBELET_EXTRA_ARGS $KUBELET_SWAP_ARGS

2：kubeadm init 參數增加ignore-preflight-errors

 kubeadm init --apiserver-advertise-address=172.16.120.200  --pod-network-cidr=192.168.0.0/16 --ignore-preflight-errors "Swap"

3：在物理機上可能并不會出現該問題。

最終安裝成功

[root@k8s-host1 manifests]# kubeadm init --apiserver-advertise-address=172.16.120.200  --pod-network-cidr=192.168.0.0/16 --ignore-preflight-errors "Swap"
[init] Using Kubernetes version: v1.9.0
[init] Using Authorization modes: [Node RBAC]
[preflight] Running pre-flight checks.
        [WARNING Swap]: running with swap on is not supported. Please disable swap
        [WARNING FileExisting-crictl]: crictl not found in system path
[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 [k8s-host1 kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 172.16.120.200]
[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] Valid certificates and keys now exist in "/etc/kubernetes/pki"
[kubeconfig] Wrote KubeConfig file to disk: "admin.conf"
[kubeconfig] Wrote KubeConfig file to disk: "kubelet.conf"
[kubeconfig] Wrote KubeConfig file to disk: "controller-manager.conf"
[kubeconfig] Wrote KubeConfig file to disk: "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 30.002346 seconds
[uploadconfig] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[markmaster] Will mark node k8s-host1 as master by adding a label and a taint
[markmaster] Master k8s-host1 tainted and labelled with key/value: node-role.kubernetes.io/master=""
[bootstraptoken] Using token: 26ea24.cb987cb5cf6f29a6
[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 --token 26ea24.cb987cb5cf6f29a6 172.16.120.200:6443 --discovery-token-ca-cert-hash sha256:a2d5e0391695bb122d4a43dc951f93934a2aaa1360e00556401a49ea0ec2bdab

PS 需要記下 kubeadm join --token 26ea24.cb987cb5cf6f29a6 172.16.120.200:6443 --discovery-token-ca-cert-hash sha256:a2d5e0391695bb122d4a43dc951f93934a2aaa1360e00556401a49ea0ec2bdab，便于以后node加入到k8s集群中。

首先需要將上節生成的etcd ca等證書cp到mater主機的/etc/etcd/ssl/下

默認kubeadm安裝了一個etcd節點，非集群，非加密，所以我們必須對kube-apiserver.yaml做修改。
修改后的kube-apiserver.yaml：

apiVersion: v1
kind: Pod
metadata:
  annotations:
    scheduler.alpha.kubernetes.io/critical-pod: ""
  labels:
    component: kube-apiserver
    tier: control-plane
  name: kube-apiserver
  namespace: kube-system
spec:
  containers:
  - command:
    - kube-apiserver
    - --allow-privileged=true
    - --requestheader-username-headers=X-Remote-User
    - --requestheader-group-headers=X-Remote-Group
    - --requestheader-extra-headers-prefix=X-Remote-Extra-
    - --service-cluster-ip-range=10.96.0.0/12
    - --requestheader-client-ca-file=/etc/kubernetes/pki/front-proxy-ca.crt
    - --proxy-client-key-file=/etc/kubernetes/pki/front-proxy-client.key
    - --enable-bootstrap-token-auth=true
    - --service-account-key-file=/etc/kubernetes/pki/sa.pub
    - --tls-cert-file=/etc/kubernetes/pki/apiserver.crt
    - --kubelet-client-certificate=/etc/kubernetes/pki/apiserver-kubelet-client.crt
    - --kubelet-client-key=/etc/kubernetes/pki/apiserver-kubelet-client.key
    - --proxy-client-cert-file=/etc/kubernetes/pki/front-proxy-client.crt
    - --insecure-port=0
    - --admission-control=Initializers,NamespaceLifecycle,LimitRanger,ServiceAccount,DefaultStorageClass,DefaultTolerationSeconds,NodeRestriction,ResourceQuota
    - --requestheader-allowed-names=front-proxy-client
    - --advertise-address=172.16.120.200
    - --client-ca-file=/etc/kubernetes/pki/ca.crt
    - --secure-port=6443
    - --kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname
    - --tls-private-key-file=/etc/kubernetes/pki/apiserver.key
    - --authorization-mode=Node,RBAC
    - --etcd-servers=https://172.16.120.151:2379,https://172.16.120.152:2379,https://172.16.120.153:2379
    - --etcd-cafile=/etc/etcd/ssl/ca.pem
    - --etcd-certfile=/etc/etcd/ssl/etcd.pem
    - --etcd-keyfile=/etc/etcd/ssl/etcd-key.pem
    image: gcr.io/google_containers/kube-apiserver-amd64:v1.9.0
    livenessProbe:
      failureThreshold: 8
      httpGet:
        host: 172.16.120.200
        path: /healthz
        port: 6443
        scheme: HTTPS
      initialDelaySeconds: 15
      timeoutSeconds: 15
    name: kube-apiserver
    resources:
      requests:
        cpu: 250m
    volumeMounts:
    - mountPath: /etc/kubernetes/pki
      name: k8s-certs
      readOnly: true
    - mountPath: /etc/ssl/certs
      name: ca-certs
      readOnly: true
    - mountPath: /etc/pki
      name: ca-certs-etc-pki
      readOnly: true
    - mountPath: /etc/etcd/ssl
      name: ca-certs-etc-etcd-ssl
      readOnly: true
  hostNetwork: true
  volumes:
  - hostPath:
      path: /etc/kubernetes/pki
      type: DirectoryOrCreate
    name: k8s-certs
  - hostPath:
      path: /etc/ssl/certs
      type: DirectoryOrCreate
    name: ca-certs
  - hostPath:
      path: /etc/pki
      type: DirectoryOrCreate
    name: ca-certs-etc-pki
  - hostPath:
      path: /etc/etcd/ssl
      type: DirectoryOrCreate
    name: ca-certs-etc-etcd-ssl
status: {}

注意添加了以下四項：

--etcd-cafile=/etc/etcd/ssl/ca.pem  
--etcd-certfile=/etc/etcd/ssl/etcd.pem  
--etcd-keyfile=/etc/etcd/ssl/etcd-key.pem    
--etcd-servers=https://172.16.120.151:2379,https://172.16.120.152:2379,https://172.16.120.153:2379
# 以及掛載
 - mountPath: /etc/etcd/ssl
      name: ca-certs-etc-etcd-ssl
      readOnly: true
      
 - hostPath:
      path: /etc/etcd/ssl
      type: DirectoryOrCreate
    name: ca-certs-etc-etcd-ssl   

kubectl get componentstatuses
NAME                 STATUS    MESSAGE              ERROR
controller-manager   Healthy   ok
scheduler            Healthy   ok
etcd-1               Healthy   {"health": "true"}
etcd-0               Healthy   {"health": "true"}
etcd-2               Healthy   {"health": "true"}

我一般的做法是，依舊使用kubeadm init --apiserver-advertise-address=172.16.120.200 --pod-network-cidr=192.168.0.0/16 --ignore-preflight-errors "Swap"
主要目的是下載k8s相關組件docker鏡像等，其實就是讓kubeadm把容易忽略的工作都做了。

然后將第一臺/etc/kubernetes/下所有文件拷貝到其他master主機對應目錄下，直至其他機器master三大組件啟動成功。

至此一個完整的master高可用集群搭建完畢。