Uchechukwu Onyekwuluje's Knowledge & Brain Dumps

Kubernetes Command Tips & Cheat Sheet

Requirements

Ensure kubectl is installed and configured. See links below

kubectl test 

kubectl version --short

You should see this:

Client Version: v1.16.0
Server Version: v1.14.8

Command Cheat Sheet

Command Description Reference Links
kubectl config view View current config kubernetes
kubectl config get-contexts Get all installed contexts kubernetes
kubectl delete ns <namesapce> Delete kubernetes namespace kubernetes

Utilities
Deleting resources in bulk using regEx

# Delete all pods matching a given pattern
kubectl get pods -n mynamespace --no-headers=true | awk '/pattern1|pattern2/{print $1}'| xargs  kubectl delete -n mynamespace pod

Port Forwarding
Port-Forward allows you to access and interact with internal Kubernetes cluster processes from your localhost. You can use this method to investigate issues and make changes locally without the need to expose the services.

# Port Forwarding Command
kubectl port-forward TYPE/NAME [options] LOCAL_PORT:REMOTE_PORT

# List Services
kubectl get svc -n argocd
NAME                    TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)                      AGE
argocd-dex-server       ClusterIP   10.108.149.200   <none>        5556/TCP,5557/TCP,5558/TCP   12h
argocd-metrics          ClusterIP   10.103.23.208    <none>        8082/TCP                     12h
argocd-redis            ClusterIP   10.111.143.18    <none>        6379/TCP                     12h
argocd-repo-server      ClusterIP   10.98.189.78     <none>        8081/TCP,8084/TCP            12h
argocd-server           ClusterIP   10.97.109.37     <none>        80/TCP,443/TCP               12h
argocd-server-metrics   ClusterIP   10.108.87.103    <none>        8083/TCP                     12h

If we want to expose port 443 for argocd-server, we can run the following

kubectl port-forward svc/argocd-server -n argocd 8080:443

If you want to access port 8080 outside localhost or any local address, we can run the following

kubectl port-forward --address 0.0.0.0 svc/argocd-server -n argocd 8080:443

If you want to access port 8080 on localhost and specific addresses, we can run the following

kubectl port-forward --address localhost,192.168.1.34 svc/argocd-server -n argocd 8080:443

You can also adjust for deployments or other service as needed.

Kubernetes Context
Kubernetes assumes the default after a clean setup. As you add more namespaces, you have to pass -n <namespace> as part of the command. You can change the context to avoid repeated use of that option

kubectl get ns
NAME              STATUS   AGE
poc1              Active   19h
default           Active   20h
poc2              Active   4h
kube-node-lease   Active   20h
kube-public       Active   20h
kube-system       Active   20h

#change context
kubectl config set-context --current --namespace=poc1

Kubernetes Options
To list enabled options, type this command:

kubectl api-versions

Kubernetes ClusterRole Description
To list clusterrole description, type:

kubectl describe clusterrole.rbac

Clean Stale Kubernetes Namespace
Delete stale namespace and all resource in it

export NAMESPACE="test"
kubectl get namespace $NAMESPACE -o json > $NAMESPACE.json
# edit $NAMESPACE.json and change finilizer to an empty list
kubectl replace --raw "/api/v1/namespaces/$NAMESPACE/finalize" -f ./$NAMESPACE.json
kubectl delete pods -n $NAMESPACE --force
kubectl get namespace

Drain and Remove Pods
Move pods to a new host for maintainance or retiring hosts

export rNode="kube-node-01"
# Drain Node
kubectl drain $rNode --ignore-daemonsets --delete-emptydir-data

# Remove Node
kubectl delete node $rNode

# Un-Cordon Node to allp scheduling
kubectl uncordon $rNode

Force Delete Pods

kubectl delete pods name-of-pod --grace-period=0 --force
kubectl delete pod pod-two --force --grace-period=0 --namespace=default
kubectl patch pod pod-two -p '{"metadata":{"finalizers":null}}'

Scale in or scale out

kubectl scale --replicas=3 deployment/nginx -n nginx-demo 
kubectl scale --replicas=1 deployment/nginx -n nginx-demo

Check Rollout Status

To check the rollout status of multiple deployments in a namespace, type

deploy=$(kubectl -n namespace get deploy -o name)
for i in $deploy; do kubectl -n namespace rollout status $i; done

Check Node Taints

kubectl get nodes -o json | jq ".items[]|{name:.metadata.name, taints:.spec.taints}"

Troubleshooting Persistent Volume Claim issues

Issue: 0/3 nodes are available: 3 pod has unbound immediate PersistentVolumeClaims.