Kubernetes 安装集群

概述

kubeadm 是 kubernetes 的集群安装工具，能够快速安装 kubernetes 集群，安装 kubernetes 主要是安装它的各个镜像，而 kubeadm 已经为我们集成好了运行 kubernetes 所需的基本镜像。但由于国内的网络原因，在搭建环境时，无法拉取到这些镜像。此时我们只需要修改为阿里云提供的镜像服务即可解决该问题。

创建并修改配置

先在/usr/local/kubernetes/cluster创建目录

mkdir -p /usr/local/kubernetes/cluster
cd /usr/local/kubernetes/cluster

# 导出配置文件
kubeadm config print init-defaults --kubeconfig ClusterConfiguration > kubeadm.yml

apiVersion: kubeadm.k8s.io/v1beta2
bootstrapTokens:
- groups:
  - system:bootstrappers:kubeadm:default-node-token
  token: abcdef.0123456789abcdef
  ttl: 24h0m0s
  usages:
  - signing
  - authentication
kind: InitConfiguration
localAPIEndpoint:
  # 修改为主节点 IP
  advertiseAddress: 192.168.222.110
  bindPort: 6443
nodeRegistration:
  criSocket: /var/run/dockershim.sock
  name: kubernetes-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
# 国内不能访问 Google，修改为阿里云
imageRepository: registry.aliyuncs.com/google_containers
kind: ClusterConfiguration
# 修改版本号
kubernetesVersion: v1.17.0
networking:
  dnsDomain: cluster.local
  # 配置 POD 所在网段为我们虚拟机不重叠的网段（这里用的是 Flannel 默认网段）
  podSubnet: "10.244.0.0/16"
  serviceSubnet: 10.96.0.0/12
scheduler: {}

查看所需镜像

kubeadm config images list --config kubeadm.yml

# 输出如下
registry.aliyuncs.com/google_containers/kube-apiserver:v1.17.0
registry.aliyuncs.com/google_containers/kube-controller-manager:v1.17.0
registry.aliyuncs.com/google_containers/kube-scheduler:v1.17.0
registry.aliyuncs.com/google_containers/kube-proxy:v1.17.0
registry.aliyuncs.com/google_containers/pause:3.1
registry.aliyuncs.com/google_containers/etcd:3.3.10
registry.aliyuncs.com/google_containers/coredns:1.3.1

拉取所需镜像

kubeadm config images pull --config kubeadm.yml

# 输出如下
[config/images] Pulled registry.aliyuncs.com/google_containers/kube-apiserver:v1.17.0
[config/images] Pulled registry.aliyuncs.com/google_containers/kube-controller-manager:v1.17.0
[config/images] Pulled registry.aliyuncs.com/google_containers/kube-scheduler:v1.17.0
[config/images] Pulled registry.aliyuncs.com/google_containers/kube-proxy:v1.17.0
[config/images] Pulled registry.aliyuncs.com/google_containers/pause:3.1
[config/images] Pulled registry.aliyuncs.com/google_containers/etcd:3.3.10
[config/images] Pulled registry.aliyuncs.com/google_containers/coredns:1.3.1

安装主节点

执行以下命令初始化主节点，该命令指定了初始化时需要使用的配置文件，其中添加 --upload-certs 参数可以在后续执行加入节点时自动分发证书文件。追加的 tee kubeadm-init.log 用以输出日志。

注意： 如果安装 kubernetes 版本和下载的镜像版本不统一则会出现 timed out waiting for the condition 错误。中途失败或是想修改配置可以使用 kubeadm reset 命令重置配置，再做初始化操作即可。

 kubeadm init --config=kubeadm.yml --upload-certs | tee kubeadm-init.log

# 输出如下
Flag --experimental-upload-certs has been deprecated, use --upload-certs instead
[init] Using Kubernetes version: v1.17.0
[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/
[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'
[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] Activating the kubelet service
[certs] Using certificateDir folder "/etc/kubernetes/pki"
[certs] Generating "ca" certificate and key
[certs] Generating "apiserver-kubelet-client" certificate and key
[certs] Generating "apiserver" certificate and key
[certs] apiserver serving cert is signed for DNS names [kubernetes-master kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 192.168.141.110]
[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 [kubernetes-master localhost] and IPs [192.168.141.110 127.0.0.1 ::1]
[certs] Generating "apiserver-etcd-client" certificate and key
[certs] Generating "etcd/peer" certificate and key
[certs] etcd/peer serving cert is signed for DNS names [kubernetes-master localhost] and IPs [192.168.141.110 127.0.0.1 ::1]
[certs] Generating "etcd/healthcheck-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
[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 23.006217 seconds
[upload-config] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config-1.15" in namespace kube-system with the configuration for the kubelets in the cluster
[upload-certs] Storing the certificates in Secret "kubeadm-certs" in the "kube-system" Namespace
[upload-certs] Using certificate key:
4a351218cf34c15b04b08b7d916c27a625418145d8d3b281ec125fd2b2ac7ab5
[mark-control-plane] Marking the node kubernetes-master as control-plane by adding the label "node-role.kubernetes.io/master=''"
[mark-control-plane] Marking the node kubernetes-master as control-plane by adding the taints [node-role.kubernetes.io/master:NoSchedule]
[bootstrap-token] Using token: abcdef.0123456789abcdef
[bootstrap-token] Configuring bootstrap tokens, cluster-info ConfigMap, RBAC Roles
[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
[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 192.168.141.110:6443 --token abcdef.0123456789abcdef 
    --discovery-token-ca-cert-hash sha256:9bf3240bf1e7ae50087888a9aa35893c5f7aa924a1f3ca518782c6d8500fc1b0 

配置 kubectl

mkdir -p $HOME/.kube
cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
# 非 ROOT 用户执行
chown $(id -u):$(id -g) $HOME/.kube/config

验证是否成功

kubectl get node
# 输出如下
NAME                STATUS     ROLES    AGE     VERSION
kubernetes-master   NotReady   master   4m38s   v1.17.0

安装从节点

将 Node 节点加入到集群中很简单，只需要在 Node 服务器上安装 kubeadm，kubectl，kubelet 三个工具，然后使用 kubeadm join 命令加入即可

kubeadm join 192.168.222.110:6443 --token abcdef.0123456789abcdef 
    --discovery-token-ca-cert-hash sha256:9bf3240bf1e7ae50087888a9aa35893c5f7aa924a1f3ca518782c6d8500fc1b0
# 输出如下
[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] Reading configuration from the cluster...
[preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
[kubelet-start] Downloading configuration for the kubelet from the "kubelet-config-1.15" ConfigMap in the kube-system namespace
[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] Activating the kubelet service
[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.

验证是否成功

回到 Master 主节点查看是否安装成功

注意： 如果 Node 节点加入 Master 时配置有问题可以在 Node 节点上使用 kubeadm reset 重置配置再使用 kubeadm join 命令重新加入即可。希望在 master 节点删除 node ，可以使用 kubectl delete nodes <NAME> 删除。

kubectl get node
# 输出如下
NAME                 STATUS     ROLES    AGE   VERSION
kubernetes-master    NotReady   master   20m   v1.17.0
kubernetes-node-01   NotReady   <none>   16s   v1.17.0
kubernetes-node-02   NotReady   <none>   6s    v1.17.0

查看 Pod 状态

coredns 尚未运行，此时我们还需要安装网络插件

kubectl get pod -n kube-system -o wide
# 输出如下
NAME                                        READY   STATUS    RESTARTS   AGE     IP                NODE                 NOMINATED NODE   READINESS GATES
coredns-bccdc95cf-9s4bm                     0/1     Pending   0          24m     <none>            <none>               <none>           <none>
coredns-bccdc95cf-s8ggd                     0/1     Pending   0          24m     <none>            <none>               <none>           <none>
etcd-kubernetes-master                      1/1     Running   0          24m     192.168.222.110   kubernetes-master    <none>           <none>
kube-apiserver-kubernetes-master            1/1     Running   0          24m     192.168.222.110   kubernetes-master    <none>           <none>
kube-controller-manager-kubernetes-master   1/1     Running   0          23m     192.168.222.110   kubernetes-master    <none>           <none>
kube-proxy-8s87d                            1/1     Running   0          4m56s   192.168.222.120   kubernetes-node-01   <none>           <none>
kube-proxy-cbnlb                            1/1     Running   0          4m46s   192.168.222.121   kubernetes-node-02   <none>           <none>
kube-proxy-vwhxj                            1/1     Running   0          24m     192.168.222.110   kubernetes-master    <none>           <none>
kube-scheduler-kubernetes-master            1/1     Running   0          24m     192.168.222.110   kubernetes-master    <none>           <none>

附：扩展阅读

kubeadm init 的执行过程

• init： 指定版本进行初始化操作
• preflight： 初始化前的检查和下载所需要的 Docker 镜像文件
• kubelet-start： 生成 kubelet 的配置文件 var/lib/kubelet/config.yaml，没有这个文件 kubelet 无法启动，所以初始化之前的 kubelet 实际上启动不会成功
• certificates： 生成 Kubernetes 使用的证书，存放在 /etc/kubernetes/pki 目录中
• kubeconfig： 生成 KubeConfig 文件，存放在 /etc/kubernetes 目录中，组件之间通信需要使用对应文件
• control-plane： 使用 /etc/kubernetes/manifest 目录下的 YAML 文件，安装 Master 组件
• etcd： 使用 /etc/kubernetes/manifest/etcd.yaml 安装 Etcd 服务
• wait-control-plane： 等待 control-plan 部署的 Master 组件启动
• apiclient： 检查 Master 组件服务状态。
• uploadconfig： 更新配置
• kubelet： 使用 configMap 配置 kubelet
• patchnode： 更新 CNI 信息到 Node 上，通过注释的方式记录
• mark-control-plane： 为当前节点打标签，打了角色 Master，和不可调度标签，这样默认就不会使用 Master 节点来运行 Pod
• bootstrap-token： 生成 token 记录下来，后边使用 kubeadm join 往集群中添加节点时会用到
• addons： 安装附加组件 CoreDNS 和 kube-proxy

最后

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