kubeadm搭建K8S集群
一、环境准备
kubeadm是官方社区推出的一个用于快速部署kubernetes集群的工具。
这个工具能通过两条指令完成一个kubernetes集群的部署：
# 创建一个 Master 节点
kubeadm init
# 将一个 Node 节点加入到当前集群中
kubeadm join <Master节点的IP和端口 >
1. 安装要求
在开始之前，部署Kubernetes集群机器需要满足以下几个条件：
- 一台或多台机器，操作系统 CentOS7.x-86_x64
- 硬件配置：2GB或更多RAM，2个CPU或更多CPU，硬盘30GB或更多
- 集群中所有机器之间网络互通
- 可以访问外网，需要拉取镜像
- 禁止swap分区，swapoff -a 注释/etc/fstab里面关于swap的行
2. 准备环境
| 角色 | IP |
|---|---|
| k8s-master | 10.11.97.193 |
| k8s-node1 | 10.11.99.141 |
关闭防火墙：
$ systemctl stop firewalld $ systemctl disable firewalld
关闭selinux：
$ sed -i 's/enforcing/disabled/' /etc/selinux/config # 永久 $ setenforce 0 # 临时
关闭swap：
$ swapoff -a # 临时 $ vim /etc/fstab # 永久
设置主机名：
$ hostnamectl set-hostname <hostname>
在master添加hosts：
$ cat >> /etc/hosts << EOF 10.11.97.193 k8s-master 10.11.99.141 k8s-node1 EOF
将桥接的IPv4流量传递到iptables的链：
$ cat > /etc/sysctl.d/k8s.conf << EOF net.bridge.bridge-nf-call-ip6tables = 1 net.bridge.bridge-nf-call-iptables = 1 EOF
$ sysctl --system # 生效
时间同步：
$ yum install ntpdate -y $ ntpdate time.windows.com
3. 安装Docker/kubeadm/kubelet【所有节点】
Kubernetes默认CRI（容器运行时）为Docker，因此先安装Docker。
3.1 安装Docker
$ wget https://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo -O /etc/yum.repos.d/docker-ce.repo $ yum -y install docker-ce $ systemctl enable docker && systemctl start docker
配置镜像下载加速器：
$ cat > /etc/docker/daemon.json << EOF
{
"registry-mirrors": ["https://b9pmyelo.mirror.aliyuncs.com"]
}
EOF
$ systemctl restart docker
$ docker info
3.2 添加阿里云YUM软件源
$ 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 EOF
3.3 安装kubeadm，kubelet和kubectl
由于版本更新频繁，这里指定版本号部署：
$ yum install -y kubelet-1.19.0 kubeadm-1.19.0 kubectl-1.19.0 $ systemctl enable kubelet
4. 部署Kubernetes Master
https://kubernetes.io/zh/docs/reference/setup-tools/kubeadm/kubeadm-init/#config-file https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/#initializing-your-control-plane-node
在master上执行：
$ kubeadm init \ --apiserver-advertise-address=10.11.97.193 \ --image-repository registry.aliyuncs.com/google_containers \ --kubernetes-version v1.19.0 \ --service-cidr=10.96.0.0/12 \ --pod-network-cidr=10.245.0.0/16 \ --ignore-preflight-errors=all
- --apiserver-advertise-address 集群通告地址
- --image-repository 由于默认拉取镜像地址k8s.gcr.io国内无法访问，这里指定阿里云镜像仓库地址
- --kubernetes-version K8s版本，与上面安装的一致
- --service-cidr 集群内部虚拟网络，Pod统一访问入口
- --pod-network-cidr Pod网络，，与下面部署的CNI网络组件yaml中保持一致
或者使用配置文件引导：
$ vi kubeadm.conf apiVersion: kubeadm.k8s.io/v1beta2 kind: ClusterConfiguration kubernetesVersion: v1.18.0 imageRepository: registry.aliyuncs.com/google_containers networking: podSubnet: 10.245.0.0/16 serviceSubnet: 10.96.0.0/12 $ kubeadm init --config kubeadm.conf --ignore-preflight-errors=all
安装过程：
[root@k8s-node3 ~]# kubeadm init \
> --apiserver-advertise-address=10.11.97.193 \
> --image-repository registry.aliyuncs.com/google_containers \
> --kubernetes-version v1.19.0 \
> --service-cidr=10.96.0.0/12 \
> --pod-network-cidr=10.245.0.0/16 \
> --ignore-preflight-errors=all
W0404 15:15:58.088052 1450 configset.go:348] WARNING: kubeadm cannot validate component configs for API groups [kubelet.config.k8s.io kubeproxy.config.k8s.io]
[init] Using Kubernetes version: v1.19.0
[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/
[WARNING SystemVerification]: this Docker version is not on the list of validated versions: 20.10.5. Latest validated version: 19.03
[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 [k8s-master kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 10.11.97.193]
[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 [k8s-master localhost] and IPs [10.11.97.193 127.0.0.1 ::1]
[certs] Generating "etcd/peer" certificate and key
[certs] etcd/peer serving cert is signed for DNS names [k8s-master localhost] and IPs [10.11.97.193 127.0.0.1 ::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 19.516063 seconds
[upload-config] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config-1.19" in namespace kube-system with the configuration for the kubelets in the cluster
[upload-certs] Skipping phase. Please see --upload-certs
[mark-control-plane] Marking the node k8s-master as control-plane by adding the label "node-role.kubernetes.io/master=''"
[mark-control-plane] Marking the node k8s-master as control-plane by adding the taints [node-role.kubernetes.io/master:NoSchedule]
[bootstrap-token] Using token: 9ibx2w.7lr713ygq3q6fz5d
[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
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 10.11.97.193:6443 --token 9ibx2w.7lr713ygq3q6fz5d \
--discovery-token-ca-cert-hash sha256:292e77baeb776c807f797812616215e018a384beefec1dc1fc5f164951ca0b7d
[root@k8s-node3 ~]#
拷贝kubectl使用的连接k8s认证文件到默认路径：
mkdir -p $HOME/.kube sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config sudo chown $(id -u):$(id -g) $HOME/.kube/config $ kubectl get nodes NAME STATUS ROLES AGE VERSION k8s-master Ready master 2m v1.18.0
5. 加入Kubernetes Node
在10.11.99.141上（Node）执行。
向集群添加新节点，执行在kubeadm init输出的kubeadm join命令：
kubeadm join 10.11.97.193:6443 --token 9ibx2w.7lr713ygq3q6fz5d --discovery-token-ca-cert-hash sha256:292e77baeb776c807f797812616215e018a384beefec1dc1fc5f164951ca0b7d
默认token有效期为24小时，当过期之后，该token就不可用了。这时就需要重新创建token，操作如下：
$ kubeadm token create $ kubeadm token list $ openssl x509 -pubkey -in /etc/kubernetes/pki/ca.crt | openssl rsa -pubin -outform der 2>/dev/null | openssl dgst -sha256 -hex | sed 's/^.* //' 63bca849e0e01691ae14eab449570284f0c3ddeea590f8da988c07fe2729e924 kubeadm join 10.11.97.193:6443 --token 9ibx2w.7lr713ygq3q6fz5d --discovery-token-ca-cert-hash sha256:292e77baeb776c807f797812616215e018a384beefec1dc1fc5f164951ca0b7d
或者直接命令快捷生成：kubeadm token create --print-join-command
https://kubernetes.io/docs/reference/setup-tools/kubeadm/kubeadm-join/
6. 部署容器网络（CNI）
注意：只需要部署下面其中一个，推荐Calico。
Calico是一个纯三层的数据中心网络方案，Calico支持广泛的平台，包括Kubernetes、OpenStack等。
Calico 在每一个计算节点利用 Linux Kernel 实现了一个高效的虚拟路由器（ vRouter） 来负责数据转发，而每个 vRouter 通过 BGP 协议负责把自己上运行的 workload 的路由信息向整个 Calico 网络内传播。
此外，Calico 项目还实现了 Kubernetes 网络策略，提供ACL功能。
https://docs.projectcalico.org/getting-started/kubernetes/quickstart
wget https://docs.projectcalico.org/manifests/calico.yaml
下载完后还需要修改里面定义Pod网络（CALICO_IPV4POOL_CIDR），与前面kubeadm init指定的一样
修改完后应用清单：
$ kubectl apply -f calico.yaml $ kubectl get pods -n kube-system
7. 测试kubernetes集群
- 验证Pod工作
- 验证Pod网络通信
- 验证DNS解析
在Kubernetes集群中创建一个pod，验证是否正常运行：
$ kubectl create deployment nginx --image=nginx $ kubectl expose deployment nginx --port=80 --type=NodePort $ kubectl get pod,svc
8. 部署 Dashboard
wget https://raw.githubusercontent.com/kubernetes/dashboard/v2.0.3/aio/deploy/recommended.yaml
默认Dashboard只能集群内部访问，修改Service为NodePort类型，暴露到外部
$ vi recommended.yaml
...
kind: Service
apiVersion: v1
metadata:
labels:
k8s-app: kubernetes-dashboard
name: kubernetes-dashboard
namespace: kubernetes-dashboard
spec:
ports:
- port: 443
targetPort: 8443
nodePort: 30001
selector:
k8s-app: kubernetes-dashboard
type: NodePort
...
$ kubectl apply -f recommended.yaml
$ kubectl get pods -n kubernetes-dashboard
NAME READY STATUS RESTARTS AGE
dashboard-metrics-scraper-6b4884c9d5-gl8nr 1/1 Running 0 13m
kubernetes-dashboard-7f99b75bf4-89cds 1/1 Running 0 13m
访问地址：https://NodeIP:30001
创建service account并绑定默认cluster-admin管理员集群角色：
# 创建用户
$ kubectl create serviceaccount dashboard-admin -n kube-system
# 用户授权
$ kubectl create clusterrolebinding dashboard-admin --clusterrole=cluster-admin --serviceaccount=kube-system:dashboard-admin
# 获取用户Token
$ kubectl describe secrets -n kube-system $(kubectl -n kube-system get secret | awk '/dashboard-admin/{print $1}')
使用输出的token登录Dashboard。
9. 遇到的问题
calico插件启动后，发现pod之间网络无法通讯，查看calico的pod不为ready状态：
经查看日志：
Readiness probe failed: caliconode is not ready: BIRD is not ready: BGP not established with 10.11.99.144.
BGP无法建立连接。
解决方法：指定出口网卡。
/* 调整calicao 网络插件的网卡发现机制，修改IP_AUTODETECTION_METHOD对应的value值。官方提供的yaml文件中，ip识别策略（IPDETECTMETHOD）没有配置，即默认为first-found，这会导致一个网络异常的ip作为nodeIP被注册，
从而影响node-to-node mesh。我们可以修改成can-reach或者interface的策略，尝试连接某一个Ready的node的IP，以此选择出正确的IP。 */ // calico.yaml 文件添加以下二行 - name: IP_AUTODETECTION_METHOD value: "interface=eth0" // 配置如下 # Cluster type to identify the deployment type - name: CLUSTER_TYPE value: "k8s,bgp" # Specify interface - name: IP_AUTODETECTION_METHOD value: "interface=eth0" # Auto-detect the BGP IP address. - name: IP value: "autodetect" # Enable IPIP - name: CALICO_IPV4POOL_IPIP value: "Always" # Enable or Disable VXLAN on the default IP pool. - name: CALICO_IPV4POOL_VXLAN value: "Never"
修改参数后，重建pod，恢复正常：
