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 version
-
Client 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-info
-
Kubernetes control plane is running at https:
//127.0.0.1:6443
-
CoreDNS is running at https:
//127.0.0.1:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy
-
Metrics-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 nodes
-
NAME STATUS ROLES AGE VERSION
-
linux-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 deployments
-
NAME READY UP-TO-DATE AVAILABLE AGE
-
nginx-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 pods
-
Name: nginx-deployment
-597c48c9dd-j49bc
-
Namespace:
default
-
Priority:
0
-
Node: linux-local/
192.168
.5
.15
-
Start Time: Thu,
28 Jan
2021
10:
53:
14 +
0800
-
Labels: app=nginx-deployment
-
pod-template-hash=
597c48c9dd
-
Annotations: <none>
-
Status: Running
-
IP:
10.42
.0
.7
-
IPs:
-
IP:
10.42
.0
.7
-
Controlled By: ReplicaSet/nginx-deployment
-597c48c9dd
-
Containers:
-
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:
false
-
QoS Class: BestEffort
-
Node-Selectors: <none>
-
Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists
for
300s
-
node.kubernetes.io/unreachable:NoExecute op=Exists
for
300s
-
Events:
-
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 services
-
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
-
kubernetes ClusterIP
10.43
.0
.1 <none>
443/TCP
77m
-
nginx-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
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！
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转载：https://blog.csdn.net/zhenghongcs/article/details/114267349