1、概述

kubeadm是一工具箱，通过kubeadm工具，可以快速的创建一个最小的、可用的，并且符合最佳实践的k8s集群。

本文档介绍如何通过kubeadm工具快速部署一个k8s集群。

2、主机规划及环境准备

此处的主机配置要在所有的节点进行操作。

2.1、主机规划

IP	主机名	CPU/MEM	操作系统版本	角色	数据磁盘目录
172.20.58.83	nccztsjb-node-23	8c/16g	CentOS 7.5.1804	master	/data
172.20.58.65	nccztsjb-node-24	8c/16g	CentOS 7.5.1804	worker node	/data
172.20.58.18	nccztsjb-node-25	8c/16g	CentOS 7.5.1804	worker node	/data

本次安装的架构为1 master节点 2 node节点集群。后续也逐步会介绍如何通过kubeadm工具部署多master的高可用集群。

数据磁盘目录/data用于存放docker镜像及容器数据。

2.2、网卡MAC地址、主机UUID一致性检查

要确保各个主机的主机名、MAC地址和product_uuid是唯一的。k8s使用这些值来作为集群中节点的唯一标识。如果这些值不唯一，安装过程会失败。

主机名检查

hostname

MAC地址检查

ip link

product_uuid检查

cat /sys/class/dmi/id/product_uuid

2.3、加载br_netfilter模块

为了让ipables可以看到桥接的流量，需要加载br_netfilter模块。

通过以下的命令检查，是否加载了br_netfilter模块：

lsmod | grep br_netfilter

如果没有，可以通过以下的命令手动加载：

modprobe br_netfilter

加载后，查询模块显示结果如下：

[root@nccztsjb-node-23 ~]#  lsmod | grep br_netfilter

br_netfilter           22256  0

bridge                146976  1 br_netfilter

配置模块加载永久生效

cat <<EOF | tee /etc/modules-load.d/k8s.conf

br_netfilter

EOF

这样重启主机之后，模块会自动的进行加载。

内核参数设置

cat <<EOF | tee /etc/sysctl.d/k8s.conf

net.bridge.bridge-nf-call-ip6tables = 1

net.bridge.bridge-nf-call-iptables = 1

EOF

sysctl --system

以上配置主要是网络插件的部署对与系统的要求。

3、部署容器运行时（docker）

为了在pod中运行容器，需要使用容器运行时，本次安装使用docker运行时。kubelet通过内置的dockershim CRI与docker进行集成。

3.1、安装docker

# 1、安装必要的一些系统工具

yum install -y yum-utils device-mapper-persistent-data lvm2

# 2、添加软件源信息

yum-config-manager --add-repo https://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo

# 3、修改镜像源地址

sed -i 's+download.docker.com+mirrors.aliyun.com/docker-ce+' /etc/yum.repos.d/docker-ce.repo

# 4、更新并安装Docker-CE

yum makecache fast

yum -y install docker-ce

# 5、开启Docker服务并设置为开机启动

systemctl enable --now docker

查看docker版本及运行状态

docker version

systemctl status docker

3.2、配置docker

对docker进行配置，主要是配置cgroup driver和数据存储目录。

将docker的cgroup driver设置为systemd

cat <<EOF | tee /etc/docker/daemon.json

{

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

  "log-driver": "json-file",

  "log-level": "warn",

  "storage-driver": "overlay2",

  "log-opts": {

    "max-size": "10m",

    "max-file": "3"

    },

  "data-root": "/data/docker",

  "insecure-registries": ["0.0.0.0/0"],

  "features": {

      "buildkit": true

  }

}

EOF

重启docker，查看docker配置

systemctl restart docker

docker info |grep -iE "cgroup Driver|Docker Root"

4、安装kubeadm,kubelet,kubectl工具

在所有的机器上执行以下的安装操作。

通过yum的方式安装kubeadm kubelet,kubectl命令，当然也可以通过到github上下载的方式进行安装。

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=1

repo_gpgcheck=1

gpgkey=https://mirrors.aliyun.com/kubernetes/yum/doc/yum-key.gpg https://mirrors.aliyun.com/kubernetes/yum/doc/rpm-package-key.gpg

EOF

# 关闭selinux

setenforce 0

sed -i 's/^SELINUX=enforcing$/SELINUX=permissive/' /etc/selinux/config

# 安装kubeadm,kubelet,kubectl

yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes

# 启动并设置为开机启动

systemctl enable --now kubelet

注意：此时kubelet服务是不正常的，后续当通过kubeadm引导集群、提供kubelet具体的配置时，kubelet服务才会正常。

5、创建kubeadm的配置文件

在通过kubeadm工具初始化集群时，可以提供各种参数对集群、组件进行配置

cat <<EOF | tee kubeadm-config.yaml

kind: ClusterConfiguration

apiVersion: kubeadm.k8s.io/v1beta3

kubernetesVersion: v1.23.1  #此处为要安装的k8s的版本

imageRepository: gotok8s    #拉取镜像的库，默认从k8s.gcr.io拉取，网络上访问会有问题，使用其他包含镜像的站点

controlPlaneEndpoint: "172.20.58.83:6443" #apiserver对外地址，也是master的IP:443,后续如果要设置为高可用集群会用到

networking:

  podSubnet: "172.39.0.0/16" #pod所在的子网

---

kind: KubeletConfiguration

apiVersion: kubelet.config.k8s.io/v1beta1

cgroupDriver: systemd #配置kubelet的cgroup，要和docker保持一致

EOF

6、初始化及配置控制平面（master）

6.1、初始化

在master节点上进行初始化的操作。

kubeadm init --config kubeadm-config.yaml

安装过程拉取镜像比较慢。可以考虑将镜像拉取放到本地的harbor仓库中。

安装过程：

[root@nccztsjb-node-23 ~]# kubeadm init --config kubeadm-config.yaml

[init] Using Kubernetes version: v1.23.1

[preflight] Running pre-flight checks

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

[preflight] This might take a minute or two, depending on the speed of your internet connection

[preflight] You can also perform this action in beforehand using 'kubeadm config images pull'

[certs] Using certificateDir folder "/etc/kubernetes/pki"

[certs] Generating "ca" certificate and key

[certs] Generating "apiserver" certificate and key

[certs] apiserver serving cert is signed for DNS names [kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local nccztsjb-node-23] and IPs [10.96.0.1 172.20.58.83]

[certs] Generating "apiserver-kubelet-client" certificate and key

[certs] Generating "front-proxy-ca" certificate and key

[certs] Generating "front-proxy-client" certificate and key

[certs] Generating "etcd/ca" certificate and key

[certs] Generating "etcd/server" certificate and key

[certs] etcd/server serving cert is signed for DNS names [localhost nccztsjb-node-23] and IPs [172.20.58.83 127.0.0.1 ::1]

[certs] Generating "etcd/peer" certificate and key

[certs] etcd/peer serving cert is signed for DNS names [localhost nccztsjb-node-23] and IPs [172.20.58.83 127.0.0.1 ::1]

[certs] Generating "etcd/healthcheck-client" certificate and key

[certs] Generating "apiserver-etcd-client" certificate and key

[certs] Generating "sa" key and public key

[kubeconfig] Using kubeconfig folder "/etc/kubernetes"

[kubeconfig] Writing "admin.conf" kubeconfig file

[kubeconfig] Writing "kubelet.conf" kubeconfig file

[kubeconfig] Writing "controller-manager.conf" kubeconfig file

[kubeconfig] Writing "scheduler.conf" kubeconfig file

[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"

[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"

[kubelet-start] Starting the kubelet

[control-plane] Using manifest folder "/etc/kubernetes/manifests"

[control-plane] Creating static Pod manifest for "kube-apiserver"

[control-plane] Creating static Pod manifest for "kube-controller-manager"

[control-plane] Creating static Pod manifest for "kube-scheduler"

[etcd] Creating static Pod manifest for local etcd in "/etc/kubernetes/manifests"

[wait-control-plane] Waiting for the kubelet to boot up the control plane as static Pods from directory "/etc/kubernetes/manifests". This can take up to 4m0s

[apiclient] All control plane components are healthy after 7.514116 seconds

[upload-config] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace

[kubelet] Creating a ConfigMap "kubelet-config-1.23" in namespace kube-system with the configuration for the kubelets in the cluster

NOTE: The "kubelet-config-1.23" naming of the kubelet ConfigMap is deprecated. Once the UnversionedKubeletConfigMap feature gate graduates to Beta the default name will become just "kubelet-config". Kubeadm upgrade will handle this transition transparently.

[upload-certs] Skipping phase. Please see --upload-certs

[mark-control-plane] Marking the node nccztsjb-node-23 as control-plane by adding the labels: [node-role.kubernetes.io/master(deprecated) node-role.kubernetes.io/control-plane node.kubernetes.io/exclude-from-external-load-balancers]

[mark-control-plane] Marking the node nccztsjb-node-23 as control-plane by adding the taints [node-role.kubernetes.io/master:NoSchedule]

[bootstrap-token] Using token: nmc6sr.okga4v88tdanm4be

[bootstrap-token] Configuring bootstrap tokens, cluster-info ConfigMap, RBAC Roles

[bootstrap-token] configured RBAC rules to allow Node Bootstrap tokens to get nodes

[bootstrap-token] configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials

[bootstrap-token] configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token

[bootstrap-token] configured RBAC rules to allow certificate rotation for all node client certificates in the cluster

[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

Alternatively, if you are the root user, you can run:

  export KUBECONFIG=/etc/kubernetes/admin.conf

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 control-plane nodes by copying certificate authorities

and service account keys on each node and then running the following as root:

  kubeadm join 172.20.58.83:6443 --token nmc6sr.okga4v88tdanm4be \

	--discovery-token-ca-cert-hash sha256:53bb18482396f7f52e58061df6ce669169143f7e00b248e429f0ce2d7b1cc34e \

	--control-plane 

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

kubeadm join 172.20.58.83:6443 --token nmc6sr.okga4v88tdanm4be \

	--discovery-token-ca-cert-hash sha256:53bb18482396f7f52e58061df6ce669169143f7e00b248e429f0ce2d7b1cc34e

6.2、配置kubeconfig

当kubectl需要和集群通讯，需要用到kubeconfig文件，执行以下的命令配置kubeconfig

mkdir -p $HOME/.kube

cp -i /etc/kubernetes/admin.conf $HOME/.kube/config

chown $(id -u):$(id -g) $HOME/.kube/config

执行kubectl命令，进行验证

[root@nccztsjb-node-23 ~]# kubectl get nodes

NAME               STATUS     ROLES                  AGE     VERSION

nccztsjb-node-23   NotReady   control-plane,master   2m36s   v1.23.2

[root@nccztsjb-node-23 ~]#

[root@nccztsjb-node-23 ~]# kubectl get pods -A

NAMESPACE     NAME                                       READY   STATUS    RESTARTS   AGE

kube-system   coredns-7fc76f876d-9bwnp                   0/1     Pending   0          2m53s

kube-system   coredns-7fc76f876d-kpfgn                   0/1     Pending   0          2m53s

kube-system   etcd-nccztsjb-node-23                      1/1     Running   0          3m7s

kube-system   kube-apiserver-nccztsjb-node-23            1/1     Running   0          3m6s

kube-system   kube-controller-manager-nccztsjb-node-23   1/1     Running   0          3m6s

kube-system   kube-proxy-6xpf2                           1/1     Running   0          2m53s

kube-system   kube-scheduler-nccztsjb-node-23            1/1     Running   0          3m6s

[root@nccztsjb-node-23 ~]#

各个组件已经安装，coredns插件需要安装网络插件之后，才可正常。

7、部署容器网络插件（calico）

安装calico网络插件，用于容器间的通讯

kubectl apply -f https://docs.projectcalico.org/manifests/calico.yaml

待容器运行正常

[root@nccztsjb-node-23 ~]# kubectl get pod -A

NAMESPACE     NAME                                       READY   STATUS    RESTARTS   AGE

kube-system   calico-kube-controllers-85b5b5888d-lzdb5   1/1     Running   0          2m11s

kube-system   calico-node-7rjcq                          1/1     Running   0          2m11s

kube-system   coredns-7fc76f876d-9bwnp                   1/1     Running   0          8m48s

kube-system   coredns-7fc76f876d-kpfgn                   1/1     Running   0          8m48s

kube-system   etcd-nccztsjb-node-23                      1/1     Running   0          9m2s

kube-system   kube-apiserver-nccztsjb-node-23            1/1     Running   0          9m1s

kube-system   kube-controller-manager-nccztsjb-node-23   1/1     Running   0          9m1s

kube-system   kube-proxy-6xpf2                           1/1     Running   0          8m48s

kube-system   kube-scheduler-nccztsjb-node-23            1/1     Running   0          9m1s

查看节点状态

[root@nccztsjb-node-23 ~]# kubectl get nodes

NAME               STATUS   ROLES                  AGE     VERSION

nccztsjb-node-23   Ready    control-plane,master   9m40s   v1.23.2

[root@nccztsjb-node-23 ~]#

节点状态也正常了，OK，现在只有一个master节点的k8s集群部署完成。

注意：master上配置了taint即工作负载不可以调度上，也是符合最佳实践的。

8、加入node节点

通过以上初始化过程中提到的命令将其他的2个节点以node节点加入到集群中

kubeadm join 172.20.58.83:6443 --token nmc6sr.okga4v88tdanm4be \

	--discovery-token-ca-cert-hash sha256:53bb18482396f7f52e58061df6ce669169143f7e00b248e429f0ce2d7b1cc34e

执行过程

[root@nccztsjb-node-24 ~]# kubeadm join 172.20.58.83:6443 --token nmc6sr.okga4v88tdanm4be \

> --discovery-token-ca-cert-hash sha256:53bb18482396f7f52e58061df6ce669169143f7e00b248e429f0ce2d7b1cc34e

[preflight] Running pre-flight checks

[preflight] Reading configuration from the cluster...

[preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -o yaml'

[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"

[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"

[kubelet-start] Starting the kubelet

[kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap...

This node has joined the cluster:

* Certificate signing request was sent to apiserver and a response was received.

* The Kubelet was informed of the new secure connection details.

Run 'kubectl get nodes' on the control-plane to see this node join the cluster.

[root@nccztsjb-node-24 ~]#

注意：加入节点也有个拉取镜像的过程，需要等些时间。

在master节点查看node状态

[root@nccztsjb-node-23 ~]# kubectl get nodes

NAME               STATUS   ROLES                  AGE    VERSION

nccztsjb-node-23   Ready    control-plane,master   14m    v1.23.2

nccztsjb-node-24   Ready    <none>                 2m5s   v1.23.2

nccztsjb-node-25   Ready    <none>                 87s    v1.23.2

[root@nccztsjb-node-23 ~]#

查看pod的状态

[root@nccztsjb-node-23 ~]# kubectl get pod -A

NAMESPACE     NAME                                       READY   STATUS    RESTARTS   AGE

kube-system   calico-kube-controllers-85b5b5888d-lzdb5   1/1     Running   0          8m51s

kube-system   calico-node-5ndlp                          1/1     Running   0          3m2s

kube-system   calico-node-7rjcq                          1/1     Running   0          8m51s

kube-system   calico-node-9hm4q                          1/1     Running   0          2m24s

kube-system   coredns-7fc76f876d-9bwnp                   1/1     Running   0          15m

kube-system   coredns-7fc76f876d-kpfgn                   1/1     Running   0          15m

kube-system   etcd-nccztsjb-node-23                      1/1     Running   0          15m

kube-system   kube-apiserver-nccztsjb-node-23            1/1     Running   0          15m

kube-system   kube-controller-manager-nccztsjb-node-23   1/1     Running   0          15m

kube-system   kube-proxy-6xpf2                           1/1     Running   0          15m

kube-system   kube-proxy-j6tr8                           1/1     Running   0          2m24s

kube-system   kube-proxy-kjv9w                           1/1     Running   0          3m2s

kube-system   kube-scheduler-nccztsjb-node-23            1/1     Running   0          15m

[root@nccztsjb-node-23 ~]#

在新加的节点上也启动了calico-node的节点。

9、部署pod、测试节点间网络访问

kubectl create deployment nginx-test --image=172.20.58.152/middleware/nginx:1.21.4 --replicas=4

本次创建4个副本。

[root@nccztsjb-node-23 ~]# kubectl get pod -o wide

NAME                         READY   STATUS    RESTARTS   AGE   IP               NODE               NOMINATED NODE   READINESS GATES

nginx-test-b76c7cb54-28j4l   1/1     Running   0          28s   172.39.21.66     nccztsjb-node-25   <none>           <none>

nginx-test-b76c7cb54-pkpw2   1/1     Running   0          28s   172.39.157.194   nccztsjb-node-24   <none>           <none>

nginx-test-b76c7cb54-rbfz8   1/1     Running   0          28s   172.39.157.193   nccztsjb-node-24   <none>           <none>

nginx-test-b76c7cb54-wtch5   1/1     Running   0          28s   172.39.21.65     nccztsjb-node-25   <none>           <none>

[root@nccztsjb-node-23 ~]#

测试主机和pod间的访问：

[root@nccztsjb-node-23 ~]# ping 172.39.21.66

PING 172.39.21.66 (172.39.21.66) 56(84) bytes of data.

64 bytes from 172.39.21.66: icmp_seq=1 ttl=63 time=0.652 ms

64 bytes from 172.39.21.66: icmp_seq=2 ttl=63 time=0.492 ms

^C

--- 172.39.21.66 ping statistics ---

2 packets transmitted, 2 received, 0% packet loss, time 1000ms

rtt min/avg/max/mdev = 0.492/0.572/0.652/0.080 ms

[root@nccztsjb-node-23 ~]# ping 172.39.157.194

PING 172.39.157.194 (172.39.157.194) 56(84) bytes of data.

64 bytes from 172.39.157.194: icmp_seq=1 ttl=63 time=0.557 ms

64 bytes from 172.39.157.194: icmp_seq=2 ttl=63 time=0.422 ms

^C

--- 172.39.157.194 ping statistics ---

2 packets transmitted, 2 received, 0% packet loss, time 999ms

rtt min/avg/max/mdev = 0.422/0.489/0.557/0.071 ms

[root@nccztsjb-node-23 ~]#

测试容器间的访问

[root@nccztsjb-node-23 ~]# kubectl exec -it nginx-test-b76c7cb54-28j4l -- bash

root@nginx-test-b76c7cb54-28j4l:/# wget 172.39.157.194

bash: wget: command not found

root@nginx-test-b76c7cb54-28j4l:/# curl 172.39.157.194

<!DOCTYPE html>

<html>

<head>

<title>Welcome to nginx!</title>

<style>

html { color-scheme: light dark; }

body { width: 35em; margin: 0 auto;

font-family: Tahoma, Verdana, Arial, sans-serif; }

</style>

</head>

<body>

<h1>Welcome to nginx!</h1>

<p>If you see this page, the nginx web server is successfully installed and

working. Further configuration is required.</p>

<p>For online documentation and support please refer to

<a href="http://nginx.org/">nginx.org</a>.<br/>

Commercial support is available at

<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>

</body>

</html>

是可以通过curl访问到的。

说明，节点和容器、容器和容器之间的网络都是通的。

OK，至此通过kubeadm工具部署k8s集群完成。

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