用snap在ubuntu上構建 Microk8s，使用kubectl，部署應用

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最近在學習k8s，也就是Kubernetes的使用。

在登錄ubuntu的終端時出現了Microk8s的廣告：

 * Overheard at KubeCon: "microk8s.status just blew my mind".

     https://microk8s.io/docs/commands#microk8s.status

於是我就想試試Microk8s

GitHub項目：ubuntu/microk8s: MicroK8s is a small, fast, single-package Kubernetes for developers, IoT and edge.

官網：MicroK8s - Fast, Light, Upstream Developer Kubernetes

下載與安裝，配置PATH

安裝過程參考的官方文檔：Quick start | MicroK8s

截止2020-1-26，MicroK8s最新的版本是1.17，需要使用snap進行安裝，snap是原生安裝在ubuntu上的，直接運行：

-> % sudo snap install microk8s --classic
Download snap "microk8s" (1107) from channel "stable"                                                                    0%     1B/s ages!

可以看到下載進度很慢，需要一個世紀，但snap沒有國內的鏡像，谷歌搜索snap ubuntu mirror china發現並沒有鏡像。

之前我寫過一篇文章：新一代包管理器：snap介紹和使用：安裝，代理，禁用

解決方法有2個：

1.使用代理進行下載
2.使用snap download下載安裝包，然後傳遞文件到需要的機器。

我採用的是下載下來進行安裝：

-> % sudo snap download microk8s          
Fetching snap "microk8s"
Fetching assertions for "microk8s"
Install the snap with:
   snap ack microk8s_1107.assert
   snap install microk8s_1107.snap

-> % sudo snap ack microk8s_1107.assert 
-> % sudo snap install microk8s_1107.snap --classic

Warning: /snap/bin was not found in your $PATH. If you've not restarted your session since you
         installed snapd, try doing that. Please see https://forum.snapcraft.io/t/9469 for more
         details.

microk8s v1.17.0 from Canonical✓ installed

安裝完成，還需要添加路徑，不然會報錯：

root@ubuntu:/home/ubuntu# microk8s.status --wait-ready
Command 'microk8s.status' is available in '/snap/bin/microk8s.status'
The command could not be located because '/snap/bin' is not included in the PATH environment variable.

echo "export PATH=$PATH:/snap/bin" >> ~/.bashrc #bash
source ~/.bashrc

echo "export PATH=$PATH:/snap/bin" >> ~/.zshrc #zsh
source ~/.zshrc

添加用戶組

爲了不在使用時需要root用戶，建議添加用戶組：

-> % sudo usermod -a -G microk8s $USER
-> % su - $USER

檢查狀態並使用kubectl

檢查服務狀態：

-> # microk8s.status --wait-ready
microk8s is running
addons:
cilium: disabled
dashboard: disabled
dns: disabled
fluentd: disabled
gpu: disabled
helm: disabled
ingress: disabled
istio: disabled
jaeger: disabled
juju: disabled
knative: disabled
kubeflow: disabled
linkerd: disabled
metallb: disabled
metrics-server: disabled
prometheus: disabled
rbac: disabled
registry: disabled
storage: disabled

檢查kubectl狀態：

-> # microk8s.kubectl get nodes
NAME     STATUS   ROLES    AGE    VERSION
ubuntu   Ready    <none>   114m   v1.17.0
-> # microk8s.kubectl get services
NAME         TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.152.183.1   <none>        443/TCP   114m

部署應用

-> # microk8s.kubectl create deployment kubernetes-bootcamp --image=gcr.io/google-samples/kubernetes-bootcamp:v1
deployment.apps/kubernetes-bootcamp created
-> # microk8s.kubectl get pods
NAME                                   READY   STATUS              RESTARTS   AGE
kubernetes-bootcamp-69fbc6f4cf-ktpcm   0/1     ContainerCreating   0          38s 
-> # microk8s.kubectl get pods
NAME                                   READY   STATUS    RESTARTS   AGE
kubernetes-bootcamp-69fbc6f4cf-ktpcm   1/1     Running   0          3m10s

部署過程大約需要幾分鐘，需要注意的是下載需要網絡。

停止和啓動服務：

-> # microk8s.stop
Stopped.
-> # microk8s.start
Started.
Enabling pod scheduling
node/ubuntu already uncordoned

更多內容，未完待續。