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。
kubectl plugin list
error: unable to find any kubectl plugins in your PATHKubernetes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：
wget https://storage.googleapis.com/krew/v0.2.1/krew.tar.gz
wget https://storage.googleapis.com/krew/v0.2.1/krew.yaml
tar -zxvf krew.tar.gz./krew-linux_amd64 install --manifest=krew.yaml --archive=krew.tar.gz
Installing plugin: krew
CAVEATS:
\
| krew is now installed! To start using kubectl plugins, you need to add
| krew's installation directory to your PATH:
|
| * macOS/Linux:
| - Add the following to your ~/.bashrc or ~/.zshrc:
| export PATH="${KREW_ROOT:-$HOME/.krew}/bin:$PATH"
| - Restart your shell.
|
| * Windows: Add %USERPROFILE%\.krew\bin to your PATH environment variable
|
| Run "kubectl krew" to list krew commands and get help.
| You can find documentation at https://github.com/GoogleContainerTools/krew.
/
Installed plugin: krew
ls ~/.krew/bin/
kubectl-krew可以看到可执行文件kubectl-krew被安装到了$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:
kubectl plugin list
The following compatible plugins are available:
/root/.krew/bin/kubectl-krew2.2 使用krew
kubectl krew命令的帮助信息如下：
kubectl krew
krew is the kubectl plugin manager.
You can invoke krew through kubectl: "kubectl krew [command]..."
Usage:
krew [command]
Available Commands:
help Help about any command
info Show information about a kubectl plugin
install Install kubectl plugins
list List installed plugins
remove Uninstall plugins
search Discover kubectl plugins
update Update the local copy of the plugin index
upgrade Upgrade installed plugins to newer versions
version Show krew version and diagnostics
Flags:
-h, --help help for krew
-v, --v Level log level for V logs
Use "krew [command] --help" for more information about a command.更新本地插件索引：
kubectl krew update
Updated the local copy of plugin index.查看所有可用插件：
kubectl krew search
NAME DESCRIPTION STATUS
access-matrix Show an access matrix for all resources available
bulk-action Do bulk actions on Kubernetes resources. available
ca-cert Print the PEM CA certificate of the current clu... available
change-ns View or change the current namespace via kubectl. available
cssh SSH into Kubernetes nodes available
debug-shell Create pod with interactive kube-shell. available
exec-as Like kubectl exec, but offers a `user` flag to ... available
get-all Like 'kubectl get all', but _really_ everything available
gke-credentials Fetch credentials for GKE clusters available
ingress-nginx Interact with ingress-nginx available
krew Package manager for kubectl plugins. installed
kubesec-scan Scan Kubernetes resources with kubesec.io. available
match-name Match names of pods and other API objects available
mtail Tail logs from multiple pods matching label sel... available
node-admin List nodes and run privileged pod with chroot available
oidc-login Login for OpenID Connect authentication available
open-svc Open the Kubernetes URL(s) for the specified se... available
pod-logs Display a list of pods to get logs from available
pod-shell Display a list of pods to execute a shell in available
prompt Prompts for user confirmation when executing co... available
rbac-lookup Reverse lookup for RBAC available
rbac-view A tool to visualize your RBAC permissions. available
resource-capacity Provides an overview of resource requests, limi... available
restart Restarts a pod with the given name available
rm-standalone-pods Remove all pods without owner references available
sniff easly start a remote packet capture on kubernet... available
ssh-jump A kubectl plugin to SSH into Kubernetes nodes u... available
sudo Run Kubernetes commands impersonated as group s... available
view-secret Decode secrets available
view-serviceaccount-kubeconfig Show a kubeconfig setting to access the apiserv... available
view-utilization Shows cluster cpu and memory utilization available
warp Sync and execute local files in Pod available下面体验安装一下change-ns这个kubectl plugin：
kubectl krew install change-ns
Updated the local copy of plugin index.
Installing plugin: change-ns
CAVEATS:
\
| This plugin requires an existing KUBECONFIG file, with a `current-context` field set.
/
Installed plugin: change-nskubectl change-ns ingress-nginx
namespace changed to "ingress-nginx"
kubectl get pod
NAME READY STATUS RESTARTS AGE
nginx-ingress-controller-575d546f7c-jsvhv 1/1 Running 2 44h
nginx-ingress-default-backend-7c5fb8d8f4-ncskr 1/1 Running 2 2d这里体验安装了https://github.com/juanvallejo/kubectl-ns。