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使用 k3d 在本地运行 k8s

本文介绍如何使用 k3d 在本地快速启动一个 k8s 集群。k3d 是以容器的方式运行 K3s 集群的工具,K3s 是 Rancher 推出的经过 CNCF 认证的与 K8S 完全兼容的发行版,特点是轻量级,启动快,依赖少,适合边缘计算以及资源能力有限的机器上运行集群。k3d 的这种启动方式对平台依赖少,安装部署比较干净利落,理论上本地只需要一个 Docker 运行环境即可。

安装过程介绍

实验环境

  • 操作系统:macOS Catalina (10.15.7)
  • 容器环境:Docker Desktop for Mac 3.2.2
  • 包管理工具:Homebrew

设置 Docker 镜像加速

打开 Docker Desktop for Mac 的首选项界面,选择 Docker Engine,加入如下设置:

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{
"registry-mirrors": [
"https://8km017g6.mirror.aliyuncs.com"
]
}

之后点击 Apply & Restart 重启 Docker。

安装 k3d 和 kubectl

k3d 并不依赖于 kubectl,但是开发人员需要 kubectl 与 k3d 所创建的 k8s 集群进行通讯:

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$ brew install kubectl
$ brew install k3d

创建 k8s 集群

使用 k3d cluster create 命令即可新建集群,同样 k3d 也支持通过命令行选项传入更多的可选参数,此外,也可以经由一个 YAML 配置文件来统一进行配置。下面我们重点介绍以下后者的启动方式。

新建一个 YAML 格式的配置文件 mycluster.yaml 如下:

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apiVersion: k3d.io/v1alpha2
kind: Simple
name: mycluster
servers: 1
agents: 2
kubeAPI:
hostPort: "6443" # same as `--api-port '6443'`
ports:
- port: 8080:80 # same as `--port '8080:80@loadbalancer'`
nodeFilters:
- loadbalancer
- port: 8443:443 # same as `--port '8443:443@loadbalancer'`
nodeFilters:
- loadbalancer

上面的配置文件指定了集群的名称、集群的节点个数(servers, agents) 以及向主机暴露的端口,更多的配置参数介绍请访问 Config File - k3d

接下来我们使用上面的配置文件 mycluster.yaml ,通过向 k3d 传入 --config 参数来创建我们的集群:

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$ k3d cluster create --config /path/to/mycluster.yaml
INFO[0000] Using config file mycluster.yaml
INFO[0000] Prep: Network
INFO[0000] Created network 'k3d-mycluster'
INFO[0000] Created volume 'k3d-mycluster-images'
INFO[0001] Creating node 'k3d-mycluster-server-0'
INFO[0001] Creating node 'k3d-mycluster-agent-0'
INFO[0001] Creating node 'k3d-mycluster-agent-1'
INFO[0001] Creating LoadBalancer 'k3d-mycluster-serverlb'
INFO[0001] Starting cluster 'mycluster'
INFO[0001] Starting servers...
INFO[0001] Starting Node 'k3d-mycluster-server-0'
INFO[0007] Starting agents...
INFO[0007] Starting Node 'k3d-mycluster-agent-0'
INFO[0020] Starting Node 'k3d-mycluster-agent-1'
INFO[0028] Starting helpers...
INFO[0028] Starting Node 'k3d-mycluster-serverlb'
INFO[0029] (Optional) Trying to get IP of the docker host and inject it into the cluster as 'host.k3d.internal' for easy access
INFO[0031] Successfully added host record to /etc/hosts in 4/4 nodes and to the CoreDNS ConfigMap
INFO[0031] Cluster 'mycluster' created successfully!
INFO[0031] --kubeconfig-update-default=false --> sets --kubeconfig-switch-context=false
INFO[0031] You can now use it like this:
kubectl config use-context k3d-mycluster
kubectl cluster-info

接下来我们使用 kubectl 来查看集群 mucluster 中的基本信息:

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$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
k3d-mycluster-server-0 Ready control-plane,master 29m v1.20.2+k3s1
k3d-mycluster-agent-0 Ready <none> 29m v1.20.2+k3s1
k3d-mycluster-agent-1 Ready <none> 29m v1.20.2+k3s1

$ kubectl get pods -n kube-system
NAME READY STATUS RESTARTS AGE
local-path-provisioner-7c458769fb-sr8dk 1/1 Running 0 29m
metrics-server-86cbb8457f-t6kgk 1/1 Running 0 29m
coredns-854c77959c-fnlsh 1/1 Running 0 29m
helm-install-traefik-cbwv7 0/1 Completed 0 29m
svclb-traefik-pf5fz 2/2 Running 0 28m
svclb-traefik-5ctqj 2/2 Running 0 28m
svclb-traefik-fqdzl 2/2 Running 0 28m
traefik-6f9cbd9bd4-lpxvw 1/1 Running 0 28m

至此,一个最基本的 k8s 集群就已经创建好了。

删除集群

使用以下命令删除上面已经创建的集群:

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k3d cluster delete mycluster

部署测试应用

此处我们使用 k3d 官网提供的测试应用部署方法来启动一个 nginx:

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$ kubectl create deployment nginx --image=nginx:alpine
deployment.apps/nginx created
$ kubectl create service clusterip nginx --tcp=80:80
service/nginx created

$ cat <<EOF | kubectl apply -f -
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: nginx
annotations:
ingress.kubernetes.io/ssl-redirect: "false"
spec:
rules:
- http:
paths:
- path: /
pathType: Prefix
backend:
service:
name: nginx
port:
number: 80
EOF
ingress.networking.k8s.io/nginx created

在浏览器打开 http://localhost:8080/

localhost-8080

参考资料