k8s-debug-app

#DEBUG APPs deployment, pod, services, endpoints
kubectl get all
kubectl get deployment,svc,pods,pvc -n <namespace>

#CHECK EVENTS AND REASON BY POD
pod=$(kubectl get pods --selector="name=bad-frontend" --output=jsonpath={.items..metadata.name})
kubectl describe pod $pod

#describe the events for a pod
kubectl describe pod my-nginx | grep -A 3 Events

#debug pods
kubectl describe pods ${POD_NAME}
kubectl describe rc ${CONTROLLER_NAME} # for the replication controllers

#debug logs
kubectl logs ${POD_NAME} ${CONTAINER_NAME}

#debug previous crashes
kubectl logs --previous ${POD_NAME} ${CONTAINER_NAME}

#debug endpoints
kubectl get endpoints ${SERVICE_NAME}

#run commands to check
kubectl exec ${POD_NAME} -c ${CONTAINER_NAME} -- ${CMD} ${ARG1} ${ARG2} ... ${ARGN}
kubectl exec cassandra -- cat /var/log/cassandra/system.log
OR
kubectl exec -it container-name -- /bin/bash
OR if multiple containers in the same pod
kubectl exec -it my-pod --container main-app -- /bin/bash

#validate pods yaml files
kubectl create --validate -f mypod.yaml
kubectl delete pod,service baz foo

#get pod yaml on apiserver and compare with your pod spec
kubectl get pods/mypod -o yaml > mypod-on-apiserver.yaml
diff mypod-on-apiserver.yaml newpod.yaml


#get pods by selector and check if the list match with the expected pods to provide your service
kubectl get pods --selector=name=nginx,type=frontend

#verify the pod’s containerPort matches up with the Service’s containerPort
kubectl describe svc my-nginx

#verify the service
kubectl get svc my-nginx

kubectl exec my-nginx-3800858182-e9ihh -- printenv | grep SERVICE

#create
kubectl create -f ./nginx.yaml
#check
kubectl get pods -l run=my-nginx -o wide

#check IP
kubectl get pods -l run=my-nginx -o yaml | grep podIP

#expose a Service, create a service. But better to use a yaml file to create the service kubectl create -f ./nginx-svc.yaml
kubectl expose deployment/my-nginx

#verify your service
kubectl get svc my-nginx
kubectl describe svc my-nginx

#verify your endpoints ep
kubectl get ep my-nginx

#descale and scale, this will kill and recreate them
kubectl scale deployment my-nginx --replicas=0; kubectl scale deployment my-nginx --replicas=2;

#check if skydns kube dns is running
kubectl get services kube-dns --namespace=kube-system

#check nslookup
kubectl run curl --image=radial/busyboxplus:curl -i --tty
nslookup my-nginx

#generate self-signed certificates, generating key pair private and public key
openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout /tmp/nginx.key -out /tmp/nginx.crt -subj "/CN=my-nginx/O=my-nginx"
#convert to base64
cat /tmp/nginx.crt | base64
cat /tmp/nginx.key | base64

#edit and fill a new  nginx-secrets.yaml with the key pair secrets from above step
#and run create the secrets objects
kubectl create -f nginx-secrets.yaml