据说只有高端机器才配运行K8S，网友：1G内存的渣渣跑起来了！
据说只有高端机器才配运行K8S，网友：1G内存的渣渣跑起来了！
记得之前使用Minikube安装K8S的时候，给分3G内存都嫌小！最近发现一个K8S的经量级实现K3S，最低0.5G内存就能运行起来，安装方便，和K8S用起来区别不大。推荐给大家，希望更多没高端机器的朋友也能够把K8S玩起来！
K3S简介
K3S是一个完全符合Kubernetes的发行版。可以使用单一二进制包安装（不到 100MB），安装简单，内存只有一半，最低0.5G内存就能运行。
为什么叫K3S？开发者希望K3S在内存占用方面只有K8S的一半，Kubernetes是一个10个字母的单词，简写为K8S。那么一半大小就是5个字母的单词，简写为K3S。
安装
使用官方提供的脚本安装十分方便，一个命令即可完成安装！
使用脚本安装K3S，同时会安装其他实用程序，包括
kubectl、crictl、ctr、k3s-killall.sh和k3s-uninstall.sh；curl -sfL http://rancher-mirror.cnrancher.com/k3s/k3s-install.sh | INSTALL_K3S_MIRROR=cn sh -安装完成后提示如下信息，并且会将K3S注册为Linux中的服务；
Complete![INFO] Creating /usr/local/bin/kubectl symlink to k3s[INFO] Creating /usr/local/bin/crictl symlink to k3s[INFO] Skipping /usr/local/bin/ctr symlink to k3s, command exists in PATH at /usr/bin/ctr[INFO] Creating killall script /usr/local/bin/k3s-killall.sh[INFO] Creating uninstall script /usr/local/bin/k3s-uninstall.sh[INFO] env: Creating environment file /etc/systemd/system/k3s.service.env[INFO] systemd: Creating service file /etc/systemd/system/k3s.service[INFO] systemd: Enabling k3s unit[INFO] systemd: Starting k3s可以查看下服务的运行状态，此时显示状态为
active。[root@linux-local k3s]# systemctl status k3s● k3s.service - Lightweight Kubernetes Loaded: loaded (/etc/systemd/system/k3s.service; enabled; vendor preset: disabled) Active: active (running) since Thu 2021-01-28 10:18:39 CST; 2min 0s ago Docs: https://k3s.io Process: 14983 ExecStartPre=/sbin/modprobe overlay (code=exited, status=0/SUCCESS) Process: 14981 ExecStartPre=/sbin/modprobe br_netfilter (code=exited, status=0/SUCCESS) Main PID: 14986 (k3s-server) Tasks: 71 Memory: 776.3M
使用
我们使用kubectl命令操作K3S与之前操作Minikube中的K8S并没有什么区别，这次还是创建一个Nginx的Deployment，然后通过创建Service将其暴露到外部访问。
创建集群
由于K3S默认安装了kubectl工具，我们可以直接使用它，比如查看kubectl的版本号；
kubectl versionClient Version: version.Info{Major:"1", Minor:"20", GitVersion:"v1.20.2+k3s1", GitCommit:"1d4adb0301b9a63ceec8cabb11b309e061f43d5f", GitTreeState:"clean", BuildDate:"2021-01-14T23:52:37Z", GoVersion:"go1.15.5", Compiler:"gc", Platform:"linux/amd64"}Server Version: version.Info{Major:"1", Minor:"20", GitVersion:"v1.20.2+k3s1", GitCommit:"1d4adb0301b9a63ceec8cabb11b309e061f43d5f", GitTreeState:"clean", BuildDate:"2021-01-14T23:52:37Z", GoVersion:"go1.15.5", Compiler:"gc", Platform:"linux/amd64"}还可以查看集群详细信息；
kubectl cluster-infoKubernetes control plane is running at https://127.0.0.1:6443CoreDNS is running at https://127.0.0.1:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxyMetrics-server is running at https://127.0.0.1:6443/api/v1/namespaces/kube-system/services/https:metrics-server:/proxy查看集群中的所有Node，可以发现K3S和之前的Minikube一样创建了一个单节点的简单集群。
kubectl get nodesNAME STATUS ROLES AGE VERSIONlinux-local Ready control-plane,master 11m v1.20.2+k3s1
部署应用
指定好应用镜像并创建一个Deployment，这里创建一个Nginx应用；
kubectl create deployment nginx-deployment --image=nginx:1.10查看所有Deployment；
kubectl get deploymentsNAME READY UP-TO-DATE AVAILABLE AGEnginx-deployment 1/1 1 1 6s
查看应用
查看Pod的详细状态，包括IP地址、占用端口、使用镜像等信息；
kubectl describe podsName: nginx-deployment-597c48c9dd-j49bcNamespace: defaultPriority: 0Node: linux-local/192.168.5.15Start Time: Thu, 28 Jan 2021 10:53:14 +0800Labels: app=nginx-deployment pod-template-hash=597c48c9ddAnnotations: <none>Status: RunningIP: 10.42.0.7IPs: IP: 10.42.0.7Controlled By: ReplicaSet/nginx-deployment-597c48c9ddContainers: nginx: Container ID: containerd://560bbeefc9c5714b92ae9d0a1305c2b8746082f4aa11791a2b6e1f4288254ef0 Image: nginx:1.10 Image ID: docker.io/library/nginx@sha256:6202beb06ea61f44179e02ca965e8e13b961d12640101fca213efbfd145d7575 Port: <none> Host Port: <none> State: Running Started: Thu, 28 Jan 2021 10:53:16 +0800 Ready: True Restart Count: 0 Environment: <none> Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-fnrf7 (ro)Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: default-token-fnrf7: Type: Secret (a volume populated by a Secret) SecretName: default-token-fnrf7 Optional: falseQoS Class: BestEffortNode-Selectors: <none>Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s node.kubernetes.io/unreachable:NoExecute op=Exists for 300sEvents: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 38s default-scheduler Successfully assigned default/nginx-deployment-597c48c9dd-j49bc to linux-local Normal Pulled 38s kubelet Container image "nginx:1.10" already present on machine Normal Created 38s kubelet Created container nginx Normal Started 37s kubelet Started container nginx进入容器内部并执行
bash命令，如果想退出容器可以使用exit命令。kubectl exec -it nginx-deployment-597c48c9dd-j49bc -- bash
外部访问应用
创建一个Service来暴露
nginx-deployment这个Deployment：kubectl expose deployment/nginx-deployment --name="nginx-service" --type="NodePort" --port=80查看所有Service的状态；
kubectl get servicesNAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGEkubernetes ClusterIP 10.43.0.1 <none> 443/TCP 77mnginx-service NodePort 10.43.29.39 <none> 80:31494/TCP 10s在Linux服务器上通过CURL命令即可访问Nginx服务，此时将打印Nginx主页信息；
curl localhost:31494相比Minikube在虚拟机中安装容器化应用，K3S直接在本机上安装，直接打开防火墙端口即可在外部访问；
# 开启端口firewall-cmd --zone=public --add-port=31494/tcp --permanent# 重启防火墙firewall-cmd --reload在外部即可访问Nginx主页，访问地址：http://192.168.5.15:31494
![Image 1][]
总结
K3S确实是一个很好用的K8S发行版本，不仅安装方便，而且内存占用也降低了。由于直接在本机上安装容器化应用，外部访问也方便了！
[Image 1]: