Maximizing Kubectl: Tips For Extending Its Functionality In Kubernetes

February 02, 2023

Created by Ranjith Vijayan on Feb 02, 2023

kubectl is a user-friendly tool that makes it simple to create new commands that build upon its standard functionality. A common task when using kubectl is to list pods to check their status and see if everything is running. To achieve this, you can use the command “kubectl get pods.” However, typing this command repeatedly can become tedious. If you are coming from the docker experience, you would have developed the muscle memory to type ‘docker ps’. But if you type ‘kubectl ps’ you would get somethingl ike this

kubectl ps
error: unknown command "ps" for "kubectl"

Did you mean this?
        logs
        cp

To achieve something like docker ps with kubectl, you can create a custom script named “kubectl-ps” in the $PATH. When kubectl encounters a command it doesn’t recognize, it will search for a specific command in the PATH. In this case, it will look for the “kubectl-ps” command.

Create a file by name "kubectl-ps" in one of the directories of your $PATH
```
 #!/bin/bash

 kubectl get pods "$@"
```

Now if you type kubectl ps it will execute your custom script

 kubectl ps
 No resources found in default namespace.

Since we have added “$@” in the custom script we can pass arguments

e.g.

 kubectl ps -n kube-system 
 NAME                                      READY   STATUS      RESTARTS   AGE
 coredns-597584b69b-m8wfv                  1/1     Running     0          7d8h
 local-path-provisioner-79f67d76f8-lnq2j   1/1     Running     0          7d8h
 metrics-server-5f9f776df5-gbmrv           1/1     Running     0          7d8h
 helm-install-traefik-crd-tdpbh            0/1     Completed   0          7d8h
 helm-install-traefik-nhnkn                0/1     Completed   1          7d8h
 svclb-traefik-8b85b943-5f2nb              2/2     Running     0          7d8h
 traefik-66c46d954f-7ft6n                  1/1     Running     0          7d8h

Another example.

 kubectl ps -A                                                                                     ✔  default ○  @fsgbu-mum-1019 
 NAMESPACE         NAME                                      READY   STATUS      RESTARTS   AGE
 kube-system       coredns-597584b69b-m8wfv                  1/1     Running     0          7d8h
 kube-system       local-path-provisioner-79f67d76f8-lnq2j   1/1     Running     0          7d8h
 kube-system       metrics-server-5f9f776df5-gbmrv           1/1     Running     0          7d8h
 kube-system       helm-install-traefik-crd-tdpbh            0/1     Completed   0          7d8h
 kube-system       helm-install-traefik-nhnkn                0/1     Completed   1          7d8h
 kube-system       svclb-traefik-8b85b943-5f2nb              2/2     Running     0          7d8h
 kube-system       traefik-66c46d954f-7ft6n                  1/1     Running     0          7d8h
 ingress-test-ns   obpm-deployment-77dcdf4c78-cf2rh          1/1     Running     0          7d8h
 ingress-test-ns   obpm-deployment-77dcdf4c78-smtr9          1/1     Running     0          7d8h
 ingress-test-ns   fcubs-deployment-7ccd4b66fb-4r7fh         1/1     Running     0          7d8h
 ingress-test-ns   fcubs-deployment-7ccd4b66fb-z6xxz         1/1     Running     0          7d8h

Of course, this is a trivial example, but you get the idea. Using this extensibility feature, you can build useful, convenient utilities with kubectl, which can save a lot of time and effort.