Download the kubectl

root@photon-machine [ ~ ]# curl -LO <https://dl.k8s.io/release/v1.21.0/bin/linux/amd64/kubectl>

Install

root@photon-machine [ ~ ]# ls
go  go1.15.14.linux-amd64.tar.gz  kind  kubectl

root@photon-machine [ ~ ]# mv kubectl /usr/local/bin

root@photon-machine [ ~ ]# chmod +x /usr/local/bin/kubectl 
root@photon-machine [ ~ ]# kubectl version
Client Version: version.Info{Major:"1", Minor:"21", GitVersion:"v1.21.0", GitCommit:"cb303e613a121a29364f75cc67d3d580833a7479", GitTreeState:"clean", BuildDate:"2021-04-08T16:31:21Z", GoVersion:"go1.16.1", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"21", GitVersion:"v1.21.1", GitCommit:"5e58841cce77d4bc13713ad2b91fa0d961e69192", GitTreeState:"clean", BuildDate:"2021-05-21T23:01:33Z", GoVersion:"go1.16.4", Compiler:"gc", Platform:"linux/amd64"}