[雲端] K8s / env / K3s
===
###### tags: `雲端 / K8s`
###### tags: `雲端`, `K8s`, `K3s`

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[TOC]

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## 何謂 K3S
- ==K8S 的輕量版(lightweight)==
- GitHub
- https://github.com/rancher/k3s

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## [K3S 的起源](https://www.ithome.com.tw/news/129110)
- ### 目的
- 為了 Rio 的容器解決方案
- ### 解決方法
- Rio 需要在 K8S 上運作
- 所以在 Rio 解決方案中，放入了完整的 K8S 叢集
- ### 持續改良
- 起因
- 發現 Rio 佔用太多記憶體
- 解決方案
- 刪除不必要的 K8S 元件，持續做實驗探索
- **最終成果**
- 因移除 K8S 的老舊以及 Alpha 測試功能，能大幅降低 K8S 的大小
- 從 Rio 專案中，獨立出 K3S
- K3S 是 ==40MB== 的二進位檔
- 包含運作 K8S 的所有資源
- 符合 CNCF 標準

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## K3S 的名稱由來？
- [Kubes = K3S](https://github.com/rancher/k3s/issues/55)
- KUSO 一下

    k3s 
    = k + ( len("ubernete") - len("heavy")) + s
    = k + (8 - 5) + s
    = k + 3 + s
    = k3s

    k8s ，把 8 砍一半，變成 3
    表示 k3s 是輕量版？

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## K3S 核心元件
- **K8S 核心元件**
- Runtime, iptables、socat、du 等
- Containerd . . . . . . . . . . . . (管理完整的容器生命週期)
- Flannel . . . . . . . . . . . . . . . (管理跨主機 docker 網路)
- CoreDNS . . . . . . . . . . . . . ([CNCF 孵化畢業的開源 DNS 專案](https://k2r2bai.com/2019/09/24/ironman2020/day09/))
- Traefik Ingress 控制器 . . . ([實現負載平衡?](https://ithelp.ithome.com.tw/articles/10196261))
- 基於主機連接埠的服務負載平衡器
- \------------------------------------------------------------
利用這些元件，打造出符合 CNCF 標準的叢集

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## K3s 之安裝
- [Get Started](https://k3s.io/)

    chmod +x k3s
    sudo k3s server &
    # Kubeconfig is written to /etc/rancher/k3s/k3s.yaml
    sudo k3s kubectl get node

- ```docker rm -f $(docker ps -aq)```

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## K3D
- ### 何謂 K3D
- ==k3s in docker==
- GitHub
- https://github.com/rancher/k3d
- 官網
- https://k3d.io/
- ### Hello World
- https://github.com/rancher/k3d#k3s-in-docker
- https://asciinema.org/a/330413

            $ k3d create cluster demo --workers 3
            
            $ k3d list
            +-------------+------------------------------------+---------+---------+
            |    NAME     |               IMAGE                | STATUS  | WORKERS |
            +-------------+------------------------------------+---------+---------+
            | k3s-default | docker.io/rancher/k3s:v1.17.3-k3s1 | running |   3/3   |
            +-------------+------------------------------------+---------+---------+
            
            $ k3d get-kubeconfig
            /home/diatango_lin/.config/k3d/k3s-default/kubeconfig.yaml
            
            $ echo $KUBECONFIG
            /home/diatango_lin/.config/k3d/k3s-default/kubeconfig.yaml

- ### [k3d create](https://ithelp.ithome.com.tw/articles/10218724)
- case1

        $ k3d create
        INFO[0000] Created cluster network with ID 3b2f3fe00cbcdf64e39801c24dd3402158000ec75bd13b7912bb6aa41086ae84 
        INFO[0000] Created docker volume  k3d-k3s-default-images 
        INFO[0000] Creating cluster [k3s-default]               
        INFO[0000] Creating server using docker.io/rancher/k3s:v1.17.3-k3s1... 
        INFO[0001] SUCCESS: created cluster [k3s-default]       
        INFO[0001] You can now use the cluster with:

        export KUBECONFIG="$(k3d get-kubeconfig --name='k3s-default')"
        kubectl cluster-info

        $ echo $KUBECONFIG
        /home/diatango_lin/.config/k3d/k3s-default/kubeconfig.yaml

- case2

        $ k3d create
        FATA[0000]  Couldn't create network
        Error response from daemon: could not find an available, non-overlapping IPv4 address pool among the defaults to assign to the network 

- 可能解法1(尚未驗證)
- [TLS 证书错误，以下错误表明证书可能不匹配](https://k8smeetup.github.io/docs/setup/independent/troubleshooting-kubeadm/)
- [会自动从 kubeadm 创建的集群获取 master 的默认管理员凭证（/etc/kubernetes/admin.conf）](https://k8smeetup.github.io/docs/admin/kubeadm/)
- 可能解法2

        k3d list
        k3d stop k3s-default
        k3d delete k3s-default
        k3d list

在重建就好了？？
[](https://i.imgur.com/RwJzTeN.png)

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## 教學資源
- [[HackMD] K8S 筆記](https://hackmd.io/4WCTdFoCS56DYlVd9yZ5ow#系列文章)
- [[Youtube] Intro to k3s Lightweight Kubernetes Online training](https://youtu.be/FrGpJNI8na4?t=256)

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## 參考資料
- [[Day05]K3d (K3s In Docker) 如何安裝](https://ithelp.ithome.com.tw/articles/10218724)
- [6000个边缘Kubernetes节点驱动城市80万次智能停车，如何成为可能？](https://segmentfault.com/a/1190000018484513)
- [邊緣運算之容器管理工具 - K3s 之介紹與玩耍](https://bestsamina.github.io/posts/2019-10-10-k3s-intro-and-play/)
- [Rancher釋出K3s！史上最輕量K8s發行版，賦能邊緣計算](https://www.itread01.com/content/1551328803.html)
- [What’s the difference between k3s vs k8s](https://www.civo.com/blog/k8s-vs-k3s)
- [[K3s] 邊緣運算落伍了! 3分鐘看懂Edge Intelligence邊緣智能(上集)](https://www.youtube.com/watch?v=RHVgRk8P97s&feature=youtu.be&t=113s)
- Containerized Computing Environment
容器化計算環境
- Computing Resource Management
計算資源管理
- Easy to build a high performance/availability microservices
易於建構高效能/高可用性的微服務