Kubernetes Scripts

A collection of scripts for various tasks in Kubernetes.

Usage

Each script has a usage function. See usage with

$ <script> --help

Scripts

• findEmptyNamespaces.sh: Loop over all namespaces in a cluster and find empty ones.
• getPodsTopCSV.sh: Get a pod's cpu and memory usage (optionally per container) written as CSV formatted file.
• getResourcesCSV.sh: Get all pods resources requests and limits per container in a CSV format with values normalized. CSV format is very automation friendly and is great for pasting in an Excel or Google sheet for further processing.
• getRestartingPods.sh: Get all pods (all or single namespace) that have restarts detected in one or more containers. Formatted in CSV.
• podReady: Simple script to check if pod is really ready. Check status is 'Running' and that all containers are ready. Returns 0 if ready. Returns 1 if not ready.

One liners

Kubectl

See all custer nodes load (top)

kubectl top nodes

Get cluster events

# All cluster
kubectl get events

# Specific namespace events
kubectl get events --namespace=kube-system

Get all cluster nodes IPs and names

# Single call to K8s API
kubectl get nodes -o json | grep -A 12 addresses

# A loop for more flexibility
for n in $(kubectl get nodes -o name); do \
  echo -e "\nNode ${n}"; \
  kubectl get ${n} -o json | grep -A 8 addresses; \
done

See all cluster nodes CPU and Memory requests and limits

kubectl describe nodes | grep -A 3 "Resource .*Requests .*Limits"

Get all labels attached to all pods in a namespace

for a in $(kubectl get pods -n namespace1 -o name); do \
  echo -e "\nPod ${a}"; \
  kubectl -n namespace1 describe ${a} | awk '/Labels:/,/Annotations/' | sed '/Annotations/d'; \
done

Forward local port to a pod or service

# Forward localhost port 8080 to a specific pod exposing port 8080
kubectl port-forward -n namespace1 web 8080:8080

# Forward localhost port 8080 to a specific web service exposing port 80
kubectl port-forward -n namespace1 svc/web 8080:80

Port forwarding

• A great tool for port forwarding all services in a namespace + adding aliases to /etc/hosts is kubefwd. Note that this requires root or sudo to allow temporary editing of /etc/host.

# Port forward all service in namespace1
kubefwd svc -n namespace1

Extract and decode a secret's value

# Get the value of the postgresql password
kubectl get secret -n namespace1 my-postgresql -o jsonpath="{.data.postgres-password}" | base64 --decode

Copy secret from namespace1 to namespace2

kubectl get secret my-secret --namespace namespace1 -o yaml | sed "/namespace:/d" | kubectl apply --namespace=namespace2 -f -

Start a shell in a temporary pod

Note - Pod will terminate once exited

# Ubuntu
kubectl run --generator=run-pod/v1 my-ubuntu --rm -i -t --image ubuntu -- bash

# CentOS
kubectl run --generator=run-pod/v1 my-centos --rm -i -t --image centos:8 -- bash

# Alpine
kubectl run --generator=run-pod/v1 my-alpine --rm -i -t --image alpine:3.10 -- sh

# Busybox
kubectl run --generator=run-pod/v1 my-busybox --rm -i -t --image busybox -- sh

Get formatted list of container images in pods

Useful for listing all running containers in your cluster

kubectl get pod --all-namespaces \
    -o=jsonpath='{range .items[*]}{.metadata.namespace}, {.metadata.name}, {.spec.containers[].image}{"\n"}'

Look into a few more examples of listing containers

Get current replica count on all HPAs (Horizontal Pod Autoscaler)

kubectl get hpa --all-namespaces -o=custom-columns=NAME:.metadata.name,REPLICAS:.status.currentReplicas | sort -k2 -n -r

Helm

NOTE: It is recommended to move to Helm v3, which does not use tiller anymore.

Helm v2 on an RBAC enabled cluster

This will give tiller cluster-admin role

kubectl -n kube-system create sa tiller && \
    kubectl create clusterrolebinding tiller --clusterrole cluster-admin --serviceaccount=kube-system:tiller && \
    helm init --service-account tiller

Helm template

View the templates generated by helm install. Useful for seeing the actual templates generated by helm before deploying.
Can also be used for deploying the templates generated when cannot use Tiller

helm template <chart>

Debug helm install

• Debug a helm install. Useful for seeing the actual values resolved by helm before deploying

helm install --debug --dry-run <chart>

Rolling restart

Roll a restart across all replicas of a Deployment or StatefulSet with zero downtime

# Deployment
kubectl -n <namespace> rollout restart deployment <deployment-name>

# StatefulSet
kubectl -n <namespace> rollout restart statefulsets <statefulset-name>