k8s初始化过程解析

[root@k8s-master ~]# kubeadm init
–apiserver-advertise-address=10.10.10.100
–image-repository registry.aliyuncs.com/google_containers
–kubernetes-version v1.25.0
–service-cidr=10.1.0.0/16
–pod-network-cidr=10.2.0.0/16
–cri-socket /var/run/cri-dockerd.sock
–service-dns-domain=cluster.local
–ignore-preflight-errors=all

W0219 22:03:38.471584 10600 initconfiguration.go:119] Usage of CRI endpoints without URL scheme is deprecated and can cause kubelet errors in the future. Automatically prepending scheme “unix” to the “criSocket” with value “/var/run/cri-dockerd.sock”. Please update your configuration!
[init] Using Kubernetes version: v1.25.0

1、[preflight] 环境检查和拉取镜像 kubeadm config images pull

[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’

2、[cert] 生成k8s证书和etcd证书。

[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 [10.1.0.1 10.10.10.100]
[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 [10.10.10.100 127.0.0.1 ::1]
[certs] Generating “etcd/peer” certificate and key
[certs] etcd/peer serving cert is signed for DNS names [k8s-master localhost] and IPs [10.10.10.100 127.0.0.1 ::1]
[certs] Generating “etcd/healthcheck-client” certificate and key
[certs] Generating “apiserver-etcd-client” certificate and key
[certs] Generating “sa” key and public key

3、[kubeconfig] 生成kubeconfig文件，可以理解为认证文件。链接apiserver认证

[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”

4、[kubelet-start] 生成kubelet配置文件，启动kubelet

[kubelet-start] Writing kubelet configuration to file “/var/lib/kubelet/config.yaml”
[kubelet-start] Starting the kubelet

5、[control-plane] 部署管理节点组件，用镜像启动容器，可以使用命令查看： kubectl get pods -n kube-system

[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”

6、[etcd] 部署etcd数据库，用镜像启动容器

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

7、[wait-control-plane] 等待管理面板

[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

8、[apiclient] 检测所有控制面板状态

[apiclient] All control plane components are healthy after 13.004448 seconds

9、[upload-config] 上传配置文件到k8s集群中

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

10、[kubelet] 配置文件存储到master节点中

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

11、[upload-certs] 上传证书存储到k8s集群中

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

12、[mark-control-plane] 给管理节点添加一个标签：[node-role.kubernetes.io/master(deprecated) node-role.kubernetes.io/control-plane node.kubernetes.io/exclude-from-external-load-balancers]，并且添加一个污点：[node-role.kubernetes.io/master:NoSchedule]

[mark-control-plane] Marking the node k8s-master as control-plane by adding the labels: [node-role.kubernetes.io/control-plane node.kubernetes.io/exclude-from-external-load-balancers]
[mark-control-plane] Marking the node k8s-master as control-plane by adding the taints [node-role.kubernetes.io/control-plane:NoSchedule]

13、[bootstrap-token] 自动为每个节点颁发证书

[bootstrap-token] Using token: hjdyqz.byzmutnkmn448i5z
[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

14、[kubelet-finalize] 更新“/etc/kubernetes/kubelet.conf”以指向可旋转的kubelet客户端证书和密钥

[kubelet-finalize] Updating “/etc/kubernetes/kubelet.conf” to point to a rotatable kubelet client certificate and key

15、[addons] 部署相关插件，coreDNS、kube-proxy

[addons] Applied essential addon: CoreDNS
[addons] Applied essential addon: kube-proxy

16、代表K8S-master已经成功安装

Your Kubernetes control-plane has initialized successfully!

To start using your cluster, you need to run the following as a regular user:

17、创建k8s集群配置文件，制订了，默认的ssl证书在哪，api-server的地址，等信息

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

18、pod分布再多个机器上，pod互相之间链接，得部署，集群网络，选用网络插件

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/

19、使用如下命令，将k8s-node加入集群即可

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

kubeadm join 10.10.10.100:6443 --token hjdyqz.byzmutnkmn448i5z
–discovery-token-ca-cert-hash sha256:18ce7af434e99a8edd527be3ea83603e68c50fb676b7cf9eeeb169f5ded88b7f

k8s 初始化后，查看master节点都启动了那些端口

k8s初始化node节点加入到master节点后都启动了那些端口

pod是如何被创建到目标机器上的（原理流程）？

1. 在master节点上，写yaml描述你对容器的运行要求，创建pod的要求，eg：install-mysql.yml
2. （kubectl create -f install-mysql.yml）使用kubectl命令去创建，应用这个资源描述文件，才会涉及k8s组件交互发出请求，我需要创建一个pod去运行mysql了，请求发给谁？（api-server）
3. 验证kubectl命令发来的请求是否被允许，利用本地的https证书，直接写入kubectl配置文件的该请求被允许后才会被执行
4. api-server将mysql-pod创建的信息记录到etcd数据库中（数据库记录了一些信息， mysql镜像版本，容器名，是否需要暴露端口）
5. api-server会通知下一个组件，调度器组件，schedule准备pod调度
6. schedule调度，回去etcd里面查询，部署的pod信息是什么，schedule调度判断出一个合适的node节点去部署pod（选择好了具体的机器，还未执行）
7. scheduler调度器，回告诉api-server自己决定pod要部署到哪个node节点上
8. api-server 会将这个部署信息存储到etcd里，数据库更新（mysql本身的容器信息+绑定关系，部署到那台机器上）
9. api-server会通知node节点机器，node节点机器上的kubelet去读取etcd数据库里面的信息，根据这些信息创建mysql镜像并且创建pod。