本文|层面_Kubernetes概述

篇首语：本文由编程笔记#小编为大家整理，主要介绍了Kubernetes概述相关的知识，希望对你有一定的参考价值。

前言

本文搜集大量关于Kubernetes的文章&＃xff0c;取其精华&＃xff0c;去其糟粕&＃xff0c;以小白的视角进行学习。

Kubernetes咱也是第一次接触&＃xff0c;甚至对Docker都没怎么玩过&＃xff0c;写的有错请及时指正。

kubernetes是什么&＃xff1f;

• 名称
  
  • Kubernetes源于希腊语&＃xff0c;意为「舵手」或「飞行员」&＃xff0c;简称是k8s&＃xff0c;用8代替[ubernete]。
• 起源
  
  • 在容器技术之前&＃xff0c;是在硬件层面实现虚拟化的虚拟机。虚拟机技术的代表是VMware和OpenStack。虚拟机虽然可以隔离出很多“子电脑”&＃xff0c;但占用空间大&＃xff0c;启动慢。而容器技术在操作系统层面实现虚拟化&＃xff0c;只需要虚拟一个小规模的环境&＃xff08;类似“沙箱”&＃xff09;&＃xff0c;启动时间快&＃xff0c;占的空间小&＃xff0c;对资源的利用率很高&＃xff08;一台主机可以同时运行几千个Docker容器&＃xff09;。
  • 目前Docker容器技术非常火热&＃xff0c;但是将Docker用于实际业务&＃xff0c;面对成千上万的容器时&＃xff0c;存在编排、管理、调度各方面的困难&＃xff0c;手里的Docker突然感觉不香了&＃xff0c;因此迫切需要一套管理系统&＃xff0c;对Docker及容器灵活高效的管理。这个时候&＃xff0c;Google家的Kubernetes闪亮登场了。

kubernetes架构

每个Kubernetes集群都需要一个Master(Control plane 控制平面)&＃xff0c;它决定资源分配&＃xff0c;运行状态检查和调度、协调通信。其他的服务器为Slave(Compute machines 计算设备|节点)&＃xff0c;主要接受和运行工作负载&＃xff0c;创建或销毁容器等。

• Master
  
  • etcd&＃xff1a;保存了整个集群的状态
  • API Server&＃xff1a;提供了资源操作的唯一入口&＃xff0c;并提供认证、授权、访问控制、API注册和发现等机制
  • Controller Manager&＃xff1a;负责维护集群的状态&＃xff0c;比如故障检测、自动扩展、滚动更新等
  • Scheduler&＃xff1a;负责资源的调度&＃xff0c;按照预定的调度策略将Pod调度到相应的机器上
• Slave(Node)
  
  • Kubelet&＃xff1a;负责维护容器的生命周期&＃xff0c;同时也负责Volume&＃xff08;CSI&＃xff09;和网络&＃xff08;CNI&＃xff09;的管理
  • Kube-proxy&＃xff1a;负责为Service提供cluster内部的服务发现和负载均衡
  • Pod&＃xff1a;Kubernetes管理的基本单元&＃xff08;最小单元&＃xff09;&＃xff0c;Pod 内部是容器&＃xff0c;Kubernetes不直接管理容器&＃xff0c;而是管理 Pod
  • Fluentd&＃xff1a;获取容器日志文件、过滤和转换日志数据
  • Flannel&＃xff1a;为 Kubernetes 提供 overlay network 的网络插件&＃xff0c;它基于 Linux TUN/TAP&＃xff0c;使用 UDP 封装 IP 包来创建 overlay 网络&＃xff0c;并借助 etcd维护网络的分配情况。

构建一个简单的Kubernetes集群

• 概述
  
  • 建议至少3台服务器&＃xff0c;每台服务器4G内存&＃xff0c;2个CPU核心以上&＃xff0c;基本架构为1台master节点&＃xff0c;2台slave节点。没有服务器的可以通过在线的测试平台https://www.katacoda.com/courses/kubernetes/playground或者https://labs.play-with-k8s.com/&＃xff08;本文所用&＃xff09;&＃xff0c;可以节点信息如下:

• 安装准备
  
  • 手工搭建 Kubernetes 集群是一件很繁琐的事情&＃xff0c;为了简化这些操作&＃xff0c;就产生了很多安装配置工具&＃xff0c;如 Kubeadm &＃xff0c;Kubespray&＃xff0c;RKE 等组件。本文使用官方提供的Kubeadm&＃xff0c;Kubeadm安装完以后&＃xff0c;就可以使用它来快速安装部署Kubernetes集群了。先安装 Master 节点&＃xff0c;然后将 Slave 节点一个个加入到集群中去。
  • 使用在线测试环境时&＃xff0c;可以省去安装准备工作&＃xff1b;完整的环境准备工作参考&＃xff1a;https://www.qikqiak.com/k8strain/k8s-basic/install/&＃xff0c;感觉把修改主机名称放到添加hosts信息前比较合适。
  • 下面只是安装下kubelet kubeadm kubectl

Ubuntu使用
apt-get install -y kubelet kubeadm kubectl --allow-unauthenticated
CentOS使用
yum -y install kubelet kubeadm kubectl

• Master节点初始化

  
  

  • 通过kubeadm init初始化Master节点

[node1 ~]$ kubeadm init --apiserver-advertise-address $(hostname -i) --pod-network-cidr 10.5.0.0/16
Initializing machine ID from random generator.
I0927 01:56:10.530784 645 version.go:252] remote version is much newer: v1.19.2; falling back to: stable-1.18
W0927 01:56:10.843108 645 configset.go:202] WARNING: kubeadm cannot validate component configs for API groups [kubelet.config.k8s.io kubeproxy.config.k8s.io]
[init] Using Kubernetes version: v1.18.9
[preflight] Running pre-flight checks
[WARNING Service-Docker]: docker service is not active, please run &＃39;systemctl start docker.service&＃39;
[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 FileContent--proc-sys-net-bridge-bridge-nf-call-iptables]: /proc/sys/net/bridge/bridge-nf-call-iptables does not exist
[preflight] The system verification failed. Printing the output from the verification:
KERNEL_VERSION: 4.4.0-179-generic
DOCKER_VERSION: 19.03.11
DOCKER_GRAPH_DRIVER: vfs
OS: Linux
CGROUPS_CPU: enabled
CGROUPS_CPUACCT: enabled
CGROUPS_CPUSET: enabled
CGROUPS_DEVICES: enabled
CGROUPS_FREEZER: enabled
CGROUPS_MEMORY: enabled
[WARNING SystemVerification]: failed to parse kernel config: unable to load kernel module: "configs", output: "", err: exit status 1
[WARNING SystemVerification]: unsupported graph driver: vfs
[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 &＃39;kubeadm config images pull&＃39;
[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
[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 [node1 kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 192.168.0.13]
[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 [node1 localhost] and IPs [192.168.0.13 127.0.0.1 ::1]
[certs] Generating "etcd/peer" certificate and key
[certs] etcd/peer serving cert is signed for DNS names [node1 localhost] and IPs [192.168.0.13 127.0.0.1 ::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
[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"
W0927 01:56:40.015648 645 manifests.go:225] the default kube-apiserver authorization-mode is "Node,RBAC"; using "Node,RBAC"
[control-plane] Creating static Pod manifest for "kube-scheduler"
W0927 01:56:40.016844 645 manifests.go:225] the default kube-apiserver authorization-mode is "Node,RBAC"; using "Node,RBAC"
[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 24.502899 seconds
[upload-config] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config-1.18" 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 node1 as control-plane by adding the label "node-role.kubernetes.io/master&＃61;&＃39;&＃39;"
[mark-control-plane] Marking the node node1 as control-plane by adding the taints [node-role.kubernetes.io/master:NoSchedule]
[bootstrap-token] Using token: 9cxumz.aplwrc79m3v5cftk
[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
[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 192.168.0.13:6443 --token 9cxumz.aplwrc79m3v5cftk \\
--discovery-token-ca-cert-hash sha256:016cdbc248a3a47b93d0f04e08c0fe19a6891adc7e2c5886098715503d50b716
Waiting for api server to startup
Warning: kubectl apply should be used on resource created by either kubectl create --save-config or kubectl apply
daemonset.apps/kube-proxy configured
No resources found

• 执行上面打印中的以下内容配置Kubectl。&＃xff08;中间那条执行可能会报错&＃xff0c;因为在线的环境已经提前做好了链接&＃xff09;

mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config

• 这样Master的节点就配置好了&＃xff0c;并且可以使用Kubectl来进行各种操作了&＃xff0c;根据上面的提示接着往下做&＃xff0c;将Slave节点加入到集群。

• Slave节点加入集群
  
  • 在所有Slave节点执行如下的命令&＃xff08;刚刚Master init打印中的内容&＃xff09;&＃xff0c;将Slave节点加入集群&＃xff0c;正常的返回信息如下&＃xff1a;

[node2 ~]$ kubeadm join 192.168.0.13:6443 --token 9cxumz.aplwrc79m3v5cftk \\
> --discovery-token-ca-cert-hash sha256:016cdbc248a3a47b93d0f04e08c0fe19a6891adc7e2c5886098715503d50b716
Initializing machine ID from random generator.
W0927 02:06:18.571095 2665 join.go:346] [preflight] WARNING: JoinControlPane.controlPlane settings will be ignored when control-plane flag is not set.
[preflight] Running pre-flight checks
[WARNING Service-Docker]: docker service is not active, please run &＃39;systemctl start docker.service&＃39;
[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 FileContent--proc-sys-net-bridge-bridge-nf-call-iptables]: /proc/sys/net/bridge/bridge-nf-call-iptables does not exist
[preflight] The system verification failed. Printing the output from the verification:
KERNEL_VERSION: 4.4.0-179-generic
DOCKER_VERSION: 19.03.11
DOCKER_GRAPH_DRIVER: vfs
OS: Linux
CGROUPS_CPU: enabled
CGROUPS_CPUACCT: enabled
CGROUPS_CPUSET: enabled
CGROUPS_DEVICES: enabled
CGROUPS_FREEZER: enabled
CGROUPS_MEMORY: enabled
[WARNING SystemVerification]: failed to parse kernel config: unable to load kernel module: "configs", output: "", err: exit status 1
[WARNING SystemVerification]: unsupported graph driver: vfs
[preflight] Reading configuration from the cluster...
[preflight] FYI: You can look at this config file with &＃39;kubectl -n kube-system get cm kubeadm-config -oyaml&＃39;
[kubelet-start] Downloading configuration for the kubelet from the "kubelet-config-1.18" 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] 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 &＃39;kubectl get nodes&＃39; on the control-plane to see this node join the cluster.

• 在Master节点查看节点状态。coredns将在网络组建安装完成后Running起来。

[node1 ~]$ kubectl get node
NAME STATUS ROLES AGE VERSION
node1 NotReady master 10m v1.18.4
node2 NotReady 64s v1.18.4
node3 NotReady 61s v1.18.4
[node1 ~]$ kubectl get pod -n kube-system -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
coredns-66bff467f8-rgzhs 0/1 Pending 0 12m
coredns-66bff467f8-xgctv 0/1 Pending 0 12m
etcd-node1 1/1 Running 0 11m 192.168.0.13 node1
kube-apiserver-node1 1/1 Running 0 12m 192.168.0.13 node1
kube-controller-manager-node1 1/1 Running 0 11m 192.168.0.13 node1
kube-proxy-5lbv4 1/1 Running 0 12m 192.168.0.13 node1
kube-proxy-6m8xh 1/1 Running 0 3m34s 192.168.0.11 node3
kube-proxy-r5qvp 1/1 Running 0 3m37s 192.168.0.12 node2
kube-scheduler-node1 1/1 Running 0 11m 192.168.0.13 node1

• 安装网络插件
  
  • 安装

[node1 ~]$ kubectl apply -f https://raw.githubusercontent.com/cloudnativelabs/kube-router/master/daemonset/kubeadm-kuberouter.yaml
configmap/kube-router-cfg created
daemonset.apps/kube-router created
serviceaccount/kube-router created
clusterrole.rbac.authorization.k8s.io/kube-router created
clusterrolebinding.rbac.authorization.k8s.io/kube-router created

• 再次查看节点状态

[node1 ~]$ kubectl get nodesNAME STATUS ROLES AGE VERSION
node1 Ready master 36m v1.18.4
node2 Ready 26m v1.18.4
node3 Ready 26m v1.18.4
[node1 ~]$ kubectl get pod -n kube-system -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
coredns-66bff467f8-rgzhs 1/1 Running 0 36m 10.5.1.2 node2
coredns-66bff467f8-xgctv 1/1 Running 0 36m 10.5.2.2 node3
etcd-node1 1/1 Running 0 35m 192.168.0.13 node1
kube-apiserver-node1 1/1 Running 0 35m 192.168.0.13 node1
kube-controller-manager-node1 1/1 Running 0 35m 192.168.0.13 node1
kube-proxy-5lbv4 1/1 Running 0 36m 192.168.0.13 node1
kube-proxy-6m8xh 1/1 Running 0 27m 192.168.0.11 node3
kube-proxy-r5qvp 1/1 Running 0 27m 192.168.0.12 node2
kube-router-tphnv 1/1 Running 0 67s 192.168.0.13 node1
kube-router-v2btr 1/1 Running 0 67s 192.168.0.12 node2
kube-router-w85lf 1/1 Running 0 67s 192.168.0.11 node3
kube-scheduler-node1 1/1 Running 0 35m 192.168.0.13 node1

参考&＃xff1a;https://www.cnblogs.com/xiao987334176/p/12696740.html