Kubectl commands

kubectl is the CLI tool that interfaces with Kubernetes. It can work with either a local setup (such as with Docker desktop’s K8 or Minikube) or with one or more remote clusters. Most operations on K8s will be via kubectl.

1.minikube Commands

First, we need to start the local cluster. For that, we need to install minikube.

Install minikube

brew makes install easier, whether or not you are on a M1 mac. Run:

brew install minikube

followed by:

which minikube
minikube version

Starting and stopping the local cluster

Minikube uses virtualbox to isolate the local set up of kubernetes. Once installed, you can run 

minikube start

which returns the following in my case:

$ minikube start
😄  minikube v1.27.1 on Darwin 12.6 (arm64)
🆕  Kubernetes 1.25.2 is now available. If you would like to upgrade, specify: --kubernetes-version=v1.25.2
✨  Using the docker driver based on existing profile
👍  Starting control plane node minikube in cluster minikube
🚜  Pulling base image ...
🔄  Restarting existing docker container for "minikube" ...
🐳  Preparing Kubernetes v1.24.1 on Docker 20.10.17 ...
🔎  Verifying Kubernetes components...
    ▪ Using image gcr.io/k8s-minikube/storage-provisioner:v5
    ▪ Using image docker.io/kubernetesui/metrics-scraper:v1.0.8
    ▪ Using image docker.io/kubernetesui/dashboard:v2.7.0
🌟  Enabled addons: default-storageclass, storage-provisioner, dashboard
🏄  Done! kubectl is now configured to use "minikube" cluster and "default" namespace by default

Note: When minikube starts, kubectl will automatically bind to minikube’s kubectl by modifying the kubectl context. Thus, running k get pods will only return the ones running in minikube, not your remote cluster. To talk to a different cluster, use the k config use-context <context_name> command.

Once done, you can stop the cluster by running

minikube stop

Setting up shpod namespace

The k8s course recommends using shpod for a consistent shell experience. The yaml file in the link has the definition of a namespace.

k apply -f https://k8smastery.com/shpod.yaml
k attach -n shpod -it shpod

The attach command follows the syntax kubectl attach -n <namespace> --interactive --tty <contianer_name>

Once done, the pod can be terminated using

k delete -f https://k8smastery.com/shpod.yaml

2.kubectl Commands

The kubectl command needs to know which cluster to talk to and how to authenticate. This information is stored in the ~/.kube/config file. The provisioner (which can be GKE or minikube) will also provide / edit this file. The file as the IP address of the k8s server and the TLS certs for auth.

Get contexts First, you need to know which k8s cluster you are talking to. For this run: The * points to the active cluster. All kubectl commands apply to that cluster now.

k config get-contexts
CURRENT   NAME        CLUSTER    AUTHINFO   NAMESPACE
          gke_dev     gke_dev    gke_dev    default
          gke_prod    gke_prod   gke_prod   default
          gke_stage   gke_stage  gke_stage  default
*         minikube    minikube   minikube   default

Change contexts When you want to talk to a different cluster, change the cluster using the syntax k config use-context <contxtname>

k config use-context gke_dev

The run k config get-contexts to confirm the switch.

Get nodes k get nodes Nodes are the physical machines that run the Kubernetes cluster. 

(local2) ➜  Documents k get nodes
NAME       STATUS   ROLES           AGE     VERSION
minikube   Ready    control-plane   7d22h   v1.24.1

The get command is the most frequently used command. get can return output in a variety of formats:

k get nodes -o wide
NAME       STATUS   ROLES           AGE   VERSION   INTERNAL-IP    EXTERNAL-IP   OS-IMAGE             KERNEL-VERSION      CONTAINER-RUNTIME
minikube   Ready    control-plane   97d   v1.24.1   192.168.49.2   <none>        Ubuntu 20.04.4 LTS   5.10.104-linuxkit   docker://20.10.17

You can get return in json format and pipe that to a CLI tool called jq which can parse and extract certain info like this:

 k get node -o json | jq ".items[] | {name:.metadata.name} + .status.capacity"
{
  "name": "minikube",
  "cpu": "5",
  "ephemeral-storage": "61255492Ki",
  "hugepages-1Gi": "0",
  "hugepages-2Mi": "0",
  "hugepages-32Mi": "0",
  "hugepages-64Ki": "0",
  "memory": "8039792Ki",
  "pods": "110"
}

Describe node k describe node <node_name> If you want to delve into the details of how the node is configured and its health, you can run k describe node minikube.

Get namespaces k get ns

(flood_ml_local2) ➜  Documents k get ns
NAME                   STATUS   AGE
default                Active   7d22h
kube-node-lease        Active   7d22h
kube-public            Active   7d22h
kube-system            Active   7d22h
kubernetes-dashboard   Active   7d22h

Create a new namespace k create ns <ns_name>

(base) ➜  Documents k create ns argo-local
namespace/argo-local created

# verify

(base) ➜  Documents k get ns             
NAME                   STATUS   AGE
argo-local             Active   4h54m
default                Active   8d
kube-node-lease        Active   8d
kube-public            Active   8d
kube-system            Active   8d
kubernetes-dashboard   Active   8d
(base) ➜  Documents

Create argo server on k8s

(base) ➜  Documents k apply -n argo-local -f https://raw.githubusercontent.com/argoproj/argo/stable/manifests/quick-start-postgres.yaml
customresourcedefinition.apiextensions.k8s.io/clusterworkflowtemplates.argoproj.io created
customresourcedefinition.apiextensions.k8s.io/cronworkflows.argoproj.io created
....

Then forward the port to local machine:

(base) ➜  Documents k -n argo-local port-forward deployment/argo-server 2746:2746
Forwarding from 127.0.0.1:2746 -> 2746
Forwarding from [::1]:2746 -> 2746

Argo server UI is now accessible at https://localhost:2746. You may have to agree to security warnings before accessing this page.

Get pods k get pods -n <namespace>

(base) ➜  Documents k get pods -n argo-local
NAME                                   READY   STATUS    RESTARTS        AGE
argo-server-7fbf57bc87-f82wl           1/1     Running   3 (2m11s ago)   2m31s
minio-74474c548b-6hf48                 1/1     Running   0               2m31s
postgres-6b5944c545-tpnfb              1/1     Running   0               2m31s
workflow-controller-7d4bf4fd7d-x4qkk   1/1     Running   2 (2m9s ago)    2m31s
(base) ➜  Documents

Creating Argo workflow using kubectl

(base) ➜  ~ k create -n argo-local -f Documents/code/temp/wf-hello-world.yaml 
workflow.argoproj.io/hello-world-p4wlj created