kubectl plugin插件机制初体验之krew
1.kubectl插件机制简介
kubectl插件机制在Kubernetes 1.14宣布稳定，进入GA状态。kubectl的插件机制就是希望允许开发者以独立的二进制形式发布自定义的kubectl子命令。
kubectl插件可以使用任意语言开发，如可以是一个bash、python的脚本，也可以是其他语言开发编译的二进制可执行文件，只要最终将脚本或二进制可执行文件以kubectl-的前缀放到PATH中即可。使用kubectl plugin list可以在PATH中查看有哪些插件。
1kubectl plugin list
2
3error: unable to find any kubectl plugins in your PATH
Kubernetes提供了一个https://github.com/kubernetes/cli-runtime项目，便于我们使用Go语言编写kubectl插件。 官方也给了一个使用Go编写kubectl插件的例子https://github.com/kubernetes/sample-cli-plugin。
2.kubectl插件的包管理工具krew
krew是kubectl插件的管理器，使用krew可以轻松的查找、安装和管理kubectl插件。krew自己也作为一个kubectl插件存在。
2.1 安装krew
确认目标机器上已经安装了git，krew在更新本地插件索引时会用到git。
在kubernetes的管理节点上：
1wget https://storage.googleapis.com/krew/v0.2.1/krew.tar.gz
2wget https://storage.googleapis.com/krew/v0.2.1/krew.yaml
3
4tar -zxvf krew.tar.gz
1./krew-linux_amd64 install --manifest=krew.yaml --archive=krew.tar.gz
2Installing plugin: krew
3CAVEATS:
4\
5 | krew is now installed! To start using kubectl plugins, you need to add
6 | krew's installation directory to your PATH:
7 |
8 | * macOS/Linux:
9 | - Add the following to your ~/.bashrc or ~/.zshrc:
10 | export PATH="${KREW_ROOT:-$HOME/.krew}/bin:$PATH"
11 | - Restart your shell.
12 |
13 | * Windows: Add %USERPROFILE%\.krew\bin to your PATH environment variable
14 |
15 | Run "kubectl krew" to list krew commands and get help.
16 | You can find documentation at https://github.com/GoogleContainerTools/krew.
17/
18Installed plugin: krew
19
20
21ls ~/.krew/bin/
22kubectl-krew
可以看到可执行文件kubectl-krew被安装到了$HOME/.krew/bin路径下。接下来将$HOME/.krew/bin加入到PATH环境变量中。
再次查看当前可用的kubectl plugin，发现多了一个kubect-krew:
1kubectl plugin list
2The following compatible plugins are available:
3
4/root/.krew/bin/kubectl-krew
2.2 使用krew
kubectl krew命令的帮助信息如下：
1kubectl krew
2krew is the kubectl plugin manager.
3You can invoke krew through kubectl: "kubectl krew [command]..."
4
5Usage:
6 krew [command]
7
8Available Commands:
9 help Help about any command
10 info Show information about a kubectl plugin
11 install Install kubectl plugins
12 list List installed plugins
13 remove Uninstall plugins
14 search Discover kubectl plugins
15 update Update the local copy of the plugin index
16 upgrade Upgrade installed plugins to newer versions
17 version Show krew version and diagnostics
18
19Flags:
20 -h, --help help for krew
21 -v, --v Level log level for V logs
22
23Use "krew [command] --help" for more information about a command.
更新本地插件索引：
1kubectl krew update
2Updated the local copy of plugin index.
查看所有可用插件：
1kubectl krew search
2NAME DESCRIPTION STATUS
3access-matrix Show an access matrix for all resources available
4bulk-action Do bulk actions on Kubernetes resources. available
5ca-cert Print the PEM CA certificate of the current clu... available
6change-ns View or change the current namespace via kubectl. available
7cssh SSH into Kubernetes nodes available
8debug-shell Create pod with interactive kube-shell. available
9exec-as Like kubectl exec, but offers a `user` flag to ... available
10get-all Like 'kubectl get all', but _really_ everything available
11gke-credentials Fetch credentials for GKE clusters available
12ingress-nginx Interact with ingress-nginx available
13krew Package manager for kubectl plugins. installed
14kubesec-scan Scan Kubernetes resources with kubesec.io. available
15match-name Match names of pods and other API objects available
16mtail Tail logs from multiple pods matching label sel... available
17node-admin List nodes and run privileged pod with chroot available
18oidc-login Login for OpenID Connect authentication available
19open-svc Open the Kubernetes URL(s) for the specified se... available
20pod-logs Display a list of pods to get logs from available
21pod-shell Display a list of pods to execute a shell in available
22prompt Prompts for user confirmation when executing co... available
23rbac-lookup Reverse lookup for RBAC available
24rbac-view A tool to visualize your RBAC permissions. available
25resource-capacity Provides an overview of resource requests, limi... available
26restart Restarts a pod with the given name available
27rm-standalone-pods Remove all pods without owner references available
28sniff easly start a remote packet capture on kubernet... available
29ssh-jump A kubectl plugin to SSH into Kubernetes nodes u... available
30sudo Run Kubernetes commands impersonated as group s... available
31view-secret Decode secrets available
32view-serviceaccount-kubeconfig Show a kubeconfig setting to access the apiserv... available
33view-utilization Shows cluster cpu and memory utilization available
34warp Sync and execute local files in Pod available
下面体验安装一下change-ns这个kubectl plugin：
1kubectl krew install change-ns
2Updated the local copy of plugin index.
3Installing plugin: change-ns
4CAVEATS:
5\
6 | This plugin requires an existing KUBECONFIG file, with a `current-context` field set.
7/
8Installed plugin: change-ns
1kubectl change-ns ingress-nginx
2namespace changed to "ingress-nginx"
3
4
5kubectl get pod
6NAME READY STATUS RESTARTS AGE
7nginx-ingress-controller-575d546f7c-jsvhv 1/1 Running 2 44h
8nginx-ingress-default-backend-7c5fb8d8f4-ncskr 1/1 Running 2 2d
这里体验安装了https://github.com/juanvallejo/kubectl-ns。