环境： centos7 ，ip 10.2.7.212， kubeadm 1.19
省略部分：docker 安装，配置内网 docker registry，kubeadm、kubelet、kubeproxy 安装，直接从 kubeadm 配置、init 开始。
省略部分可以参考 centos7 使用 kubeadm 安装 kubernetes
1、关闭防火墙、selinux

systemctl stop firewalld
setenforce 0

2、关闭 swap

swapoff -a
cp /etc/fstab /etc/fstab-bak
cat /etc/fstab-bak | grep -v swap > /etc/fstab

3、设置主机名

hostnamectl set-hostname k8s-master

4、配置 hosts

修改 /etc/hosts

10.2.7.212  k8s-master

5、修改 sysctl.conf

修改 /etc/sysctl.conf

net.ipv4.ip_forward = 1
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1

sysctl -p

查看配置是否生效

sysctl -a |grep net.ipv4.ip_forward
sysctl -a |grep net.bridge.bridge-nf-call-iptables
sysctl -a |grep net.bridge.bridge-nf-call-ip6tables

6、kubeadm 查看默认配置文件

kubeadm config print init-defaults > default.yaml

7、修改配置文件 default.yaml

[root@k8s-master ~]# cat default.yaml 
apiVersion: kubeadm.k8s.io/v1beta2
bootstrapTokens:
- groups:
  - system:bootstrappers:kubeadm:default-node-token
  token: abcdef.0123456789abcdef
  ttl: 24h0m0s
  usages:
  - signing
  - authentication
kind: InitConfiguration
localAPIEndpoint:
  advertiseAddress: 10.2.7.212
  bindPort: 6443
nodeRegistration:
  criSocket: /var/run/dockershim.sock
  name: k8s-master
  taints:
  - effect: NoSchedule
    key: node-role.kubernetes.io/master
---
apiServer:
  timeoutForControlPlane: 4m0s
apiVersion: kubeadm.k8s.io/v1beta2
certificatesDir: /etc/kubernetes/pki
clusterName: kubernetes
controllerManager: {}
dns:
  type: CoreDNS
etcd:
  local:
    dataDir: /var/lib/etcd
imageRepository: google_containers
kind: ClusterConfiguration
kubernetesVersion: v1.19.0
networking:
  dnsDomain: cluster.local
  serviceSubnet: 10.254.0.0/16
  podSubnet: 10.253.0.0/16
scheduler: {}

8、拉取镜像

kubeadm config images pull --config=default.yaml

9、初始化 master 节点

kubeadm init --config=default.yaml

如果 master 节点高可用，需要添加 --upload-certs

kubeadm init --config=default.yaml --upload-certs 

或者使用

kubeadm init \
--apiserver-advertise-address=10.2.7.212 \
--pod-network=cidr=10.253.0.0/16 \
--service-cidr=10.254.0.0/16 \
--image-repository=docker.io

解决warning

...
[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/

[preflight] Pulling images required for setting up a Kubernetes cluster
'''

修改 /etc/docker/daemon.json，增加

"exec-opts": ["native.cgroupdriver=systemd"]

重启 docker

systemctl restart docker

重置

kubeadm reset

初始化 master

[root@k8s-master ~]# kubeadm init --config=default.yaml
[bootstrap-token] Creating the "cluster-info" ConfigMap in the "kube-public" namespace
[kubelet-finalize] Updating "/etc/kubernetes/kubelet.conf" to point to a rotatable kubelet client certificate and key
[addons] Applied essential addon: CoreDNS
[addons] Applied essential addon: kube-proxy

Your Kubernetes control-plane 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/


Then you can join any number of worker nodes by running the following on each as root:

kubeadm join 10.2.7.212:6443 --token abcdef.0123456789abcdef \
    --discovery-token-ca-cert-hash sha256:2d1c35a3c7bfa5f54fade5cb28d81700878363b37e7a2bc9c08b13da837af66a

10、添加 node 节点，按照第 9 步 提示 “kubeadm join 10.2.7.212:6443 --token abcdef.0123456789abcdef
​ --discovery-token-ca-cert-hash ”
参考 centos7 使用 kubeadm 安装 kubernetes

参考文章:
通过kubeadm离线安装k8s集群v1.15
https://kubernetes.io/docs/reference/setup-tools/kubeadm/kubeadm-init/