1. kubeadm简介

kubeadm 是 Kubernetes 官方提供的一个 CLI 工具，可以很方便的搭建一套符合官方最佳实践的最小化可用集群。当我们使用 kubeadm 搭建集群时，集群可以通过 K8S 的一致性测试，并且 kubeadm 还支持其他的集群生命周期功能，比如升级/降级等。

2. 安装kebeadm

2.1 安装前准备

• 禁用 swap

我们知道每个节点上都有个必须的组件，名为 kubelet，自 K8S 1.8 开始，启动 kubelet 时，需要禁用 swap 。或者需要更改 kubelet 的启动参数 --fail-swap-on=false。

• cat /proc/swaps

• swapoff -a

• 将 /etc/fstab 中和上一条命令中输出的，和 swap 相关的挂载点都删掉
  

• 确保要搭建集群的所有节点的 product_uuid和Mac 地址 均不相同

 /sys/class/dmi/id/product_uuid ip a

• 确保需要的端口没被占用

netstat -ntlp |grep -E '6443|23[79,80]|1025[0,1,2]'

• 部署docker

[root@slave ~]# yum install -y wget && wget https://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo -O /etc/yum.repos.d/docker-ce.repo
[root@slave ~]# yum -y install docker-ce-18.06.1.ce-3.el7
[root@slave ~]# systemctl enable docker && systemctl start docker
Created symlink from /etc/systemd/system/multi-user.target.wants/docker.service to /usr/lib/systemd/system/docker.service.

2.2 正式安装

1. 安装kubeadm

[root@slave ~]# curl -sSL https://dl.k8s.io/release/v1.11.3/bin/linux/amd64/kubeadm > /usr/bin/kubeadm
[root@slave ~]# chmod a+rx /usr/bin/kubeadm
[root@slave ~]# kubeadm version
kubeadm version: &version.Info{Major:"1", Minor:"11", GitVersion:"v1.11.3", GitCommit:"a4529464e4629c21224b3d52edfe0ea91b072862", GitTreeState:"clean", BuildDate:"2018-09-09T17:59:42Z", GoVersion:"go1.10.3", Compiler:"gc", Platform:"linux/amd64"}

2. 安装kubelet

[root@slave ~]# cat > /etc/yum.repos.d/kubernetes.repo << EOF
> 
> [kubernetes]
> name=Kubernetes
> baseurl=https://mirrors.aliyun.com/kubernetes/yum/repos/kubernetes-el7-x86_64
> enabled=1
> gpgcheck=0
> repo_gpgcheck=0
> gpgkey=https://mirrors.aliyun.com/kubernetes/yum/doc/yum-key.gpg https://mirrors.aliyun.com/kubernetes/yum/doc/rpm-package-key.gpg
[root@slave ~]# yum install -y kubelet-1.15.0 kubeadm-1.15.0 kubectl-1.15.0
[root@slave ~]# systemctl enable kubelet
Created symlink from /etc/systemd/system/multi-user.target.wants/kubelet.service to /usr/lib/systemd/system/kubelet.service.

3. 开启集群

[root@slave ~]# kubeadm init --apiserver-advertise-address=192.168.211.130 --image-repository registry.aliyuncs.com/google_containers --kubernetes-version v1.15.0 --service-cidr=10.1.0.0/16 --pod-network-cidr=10.244.0.0/16

2.3 安装踩坑总结

1. [ERROR FileContent–proc-sys-net-bridge-bridge-nf-call-iptables]:/proc/sys/net/bridge/bridge-nf-call-iptables contents are not set to 1

[root@slave ~]# kubeadm init
W0427 21:22:15.098333    7591 version.go:98] could not fetch a Kubernetes version from the internet: unable to get URL "https://dl.k8s.io/release/stable-1.txt": Get https://storage.googleapis.com/kubernetes-release/release/stable-1.txt: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
W0427 21:22:15.098507    7591 version.go:99] falling back to the local client version: v1.15.0
[init] Using Kubernetes version: v1.15.0
[preflight] Running pre-flight checks[WARNING IsDockerSystemdCheck]: detected "cgroupfs" as the Docker cgroup driver. The recommended driver is "systemd". Please follow the guide at https://kubernetes.io/docs/setup/cri/
error execution phase preflight: [preflight] Some fatal errors occurred:[ERROR FileContent--proc-sys-net-bridge-bridge-nf-call-iptables]: /proc/sys/net/bridge/bridge-nf-call-iptables contents are not set to 1
[preflight] If you know what you are doing, you can make a check non-fatal with `--ignore-preflight-errors=...`

解决方案

echo "1" >/proc/sys/net/bridge/bridge-nf-call-iptables

2. [ERROR ImagePull]: failed to pull image k8s.gcr.io/kube-controller-manager:v1.15.0

[ERROR ImagePull]: failed to pull image k8s.gcr.io/kube-apiserver:v1.15.0: output: Error response from daemon: Get https://k8s.gcr.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
, error: exit status 1[ERROR ImagePull]: failed to pull image k8s.gcr.io/kube-controller-manager:v1.15.0: output: Error response from daemon: Get https://k8s.gcr.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
, error: exit status 1[ERROR ImagePull]: failed to pull image k8s.gcr.io/kube-scheduler:v1.15.0: output: Error response from daemon: Get https://k8s.gcr.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
, error: exit status 1[ERROR ImagePull]: failed to pull image k8s.gcr.io/kube-proxy:v1.15.0: output: Error response from daemon: Get https://k8s.gcr.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
, error: exit status 1[ERROR ImagePull]: failed to pull image k8s.gcr.io/pause:3.1: output: Error response from daemon: Get https://k8s.gcr.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
, error: exit status 1[ERROR ImagePull]: failed to pull image k8s.gcr.io/etcd:3.3.10: output: Error response from daemon: Get https://k8s.gcr.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
, error: exit status 1[ERROR ImagePull]: failed to pull image k8s.gcr.io/coredns:1.3.1: output: Error response from daemon: Get https://k8s.gcr.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)
, error: exit status 1
[preflight] If you know what you are doing, you can make a check non-fatal with `--ignore-preflight-errors=...`

解决方案

kubeadm init --apiserver-advertise-address=192.168.211.130 --image-repository registry.aliyuncs.com/google_containers --kubernetes-version v1.15.0 --service-cidr=10.1.0.0/16 --pod-network-cidr=10.244.0.0/16

3. [ERROR ImagePull]: failed to pull image registry.aliyuncs.com/google_containers/kube-apiserver:v1.15.0: output: v1.15.0: Pulling from google_containers/kube-apiserver

解决方案

docker pull registry.aliyuncs.com/google_containers/kube-apiserver:v1.15.0

4. The connection to the server localhost:8080 was refused - did you specify the right host or port?

[root@slave ~]# kubectl cluster-infoTo further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.
The connection to the server localhost:8080 was refused - did you specify the right host or port?

解决方案

[root@slave ~]# echo "export KUBECONFIG=/etc/kubernetes/admin.conf" >> /etc/profile
[root@slave ~]# source /etc/profile
[root@slave ~]# kubectl get nodes
NAME    STATUS     ROLES    AGE     VERSION
slave   NotReady   master   8m39s   v1.15.0