Kubectl commands storage

kubectl commands

DEBUG
kubectl get pods -n “namespace”
kubectl get services 
kubectl get pods -n “namespace ”-o wide 
kubectl logs {pod-name}
kubectl exec -it {pod-name} -- bin/bash
get all pods from all namespaces 
kubectl get all -n namespace
kubectl describe endpoins

#Get information about our current context, ensure we're logged into the correct cluster.
kubectl config get-contexts

#Change our context if needed.
kubectl config use-context kubernetes-admin@kubernetes

#Get information about the API Server for our current context, which should be kubernetes-admin@kubernetes
kubectl cluster-info

#Get a list of API Resources available in the cluster
kubectl api-resources | more

#Using kubectl explain
kubectl explain pods | more

#Creating a pod with YAML
kubectl apply -f pod.yaml

#Let's look more closely at what we need in pod.spec and pod.spec.containers
kubectl explain pod.spec | more
kubectl explain pod.spec.containers | more

#We can use the -v option to increase the verbosity of our request.
#Display requested resource URL. Focus on VERB, API Path and Response code
kubectl get pod hello-world -v 6 

#Same output as 6, add HTTP Request Headers. Focus on application type, and User-Agent
kubectl get pod hello-world -v 7 

#Same output as 7, adds Response Headers and truncated Response Body.
kubectl get pod hello-world -v 8 

#Same output as 8, add full Response. Focus on the bottom, look for metadata
kubectl get pod hello-world -v 9 

#Watch, Exec and Log Requests
#A watch on Pods will watch on the resourceVersion on api/v1/namespaces/default/Pods
kubectl get pods --watch -v 6 &

#We can see kubectl keeps the TCP session open with the server...waiting for data.
netstat -plant | grep kubectl

#Accessing logs
kubectl logs hello-world
kubectl logs hello-world -v 6

#Get a list of all the namespaces in our cluster
kubectl get namespaces

#get a list of all the API resources and if they can be in a namespace
kubectl api-resources --namespaced=true | head
kubectl api-resources --namespaced=false | head

#Namespaces have state, Active and Terminating (when it's deleting)
kubectl describe namespaces

#Describe the details of an indivdual namespace
kubectl describe namespaces kube-system

#Get all the pods in our cluster across all namespaces. Right now, only system pods, no user workload.
#You can shorten --all-namespaces to -A
kubectl get pods --all-namespaces
kubectl get pods -A

#Get all the resource across all of our namespaces
kubectl get all --all-namespaces
kubectl get all -A

#Get a list of the pods in the kube-system namespace
kubectl get pods --namespace kube-system

#Imperatively create a namespace
kubectl create namespace playground1

#Create a collection of pods with labels assinged to each
more CreatePodsWithLabels.yaml
kubectl apply -f CreatePodsWithLabels.yaml

#Look at all the Pod labels in our cluster
kubectl get pods --show-labels

#Look at one Pod's labels in our cluster
kubectl describe pod nginx-pod-1 | head

#Query labels and selectors
kubectl get pods --selector tier=prod
kubectl get pods --selector tier=qa
kubectl get pods -l tier=prod
kubectl get pods -l tier=prod --show-labels

#Selector for multiple labels and adding on show-labels to see those labels in the output
kubectl get pods -l 'tier=prod,app=MyWebApp' --show-labels
kubectl get pods -l 'tier=prod,app!=MyWebApp' --show-labels
kubectl get pods -l 'tier in (prod,qa)'
kubectl get pods -l 'tier notin (prod,qa)'

#Output a particluar label in column format
kubectl get pods -L tier
kubectl get pods -L tier,app

#Edit an existing label
kubectl label pod nginx-pod-1 tier=non-prod --overwrite
kubectl get pod nginx-pod-1 --show-labels

#Adding a new label
kubectl label pod nginx-pod-1 another=Label
kubectl get pod nginx-pod-1 --show-labels

#Removing an existing label
kubectl label pod nginx-pod-1 another-
kubectl get pod nginx-pod-1 --show-labels

#Performing an operation on a collection of pods based on a label query
kubectl label pod --all tier=non-prod --overwrite
kubectl get pod --show-labels

#Delete all pods matching our non-prod label
kubectl delete pod -l tier=non-prod

#And we're left with nothing.
kubectl get pods --show-labels

#Kubernetes Resource Management
#Start a Deployment with 3 replicas, open deployment-label.yaml
kubectl apply -f deployment-label.yaml

#Expose our Deployment as  Service, open service.yaml
kubectl apply -f service.yaml

#Look at the Labels and Selectors on each resource, the Deployment, ReplicaSet and Pod
#The deployment has a selector for app=hello-world
kubectl describe deployment hello-world

#The ReplicaSet has labels and selectors for app and the current pod-template-hash
#Look at the Pod Template and the labels on the Pods created
kubectl describe replicaset hello-world

#The Pods have labels for app=hello-world and for the pod-temlpate-hash of the current ReplicaSet
kubectl get pods --show-labels

#Edit the label on one of the Pods in the ReplicaSet, change the pod-template-hash
kubectl label pod PASTE_POD_NAME_HERE pod-template-hash=DEBUG --overwrite

#The ReplicaSet will deploy a new Pod to satisfy the number of replicas. Our relabeled Pod still exists.
kubectl get pods --show-labels

#Let's look at how Services use labels and selectors, check out services.yaml
kubectl get service

#The selector for this serivce is app=hello-world, that pod is still being load balanced to!
kubectl describe service hello-world 

#Get a list of all IPs in the service, there's 5...why?
kubectl describe endpoints hello-world

#Get a list of pods and their IPs
kubectl get pod -o wide

#To remove a pod from load balancing, change the label used by the service's selector.
#The ReplicaSet will respond by placing another pod in the ReplicaSet
kubectl get pods --show-labels
kubectl label pod PASTE_POD_NAME_HERE app=DEBUG --overwrite

#Check out all the labels in our pods
kubectl get pods --show-labels

#Look at the registered endpoint addresses. Now there's 4
kubectl describe endpoints hello-world

#To clean up, delete the deployment, service and the Pod removed from the replicaset
kubectl delete deployment hello-world
kubectl delete service hello-world
kubectl delete pod PASTE_POD_NAME_HERE
--cascade=false to leave the pods alive

#Scheduling a pod to a node
#Scheduling is a much deeper topic, we're focusing on how labels can be used to influence it here.
kubectl get nodes --show-labels 

#Label our nodes with something descriptive
kubectl label node c1-node2 disk=local_ssd
kubectl label node c1-node3 hardware=local_gpu

#Query our labels to confirm.
kubectl get node -L disk,hardware

#Create three Pods, two using nodeSelector, one without.
more PodsToNodes.yaml
kubectl apply -f PodsToNodes.yaml

#View the scheduling of the pods in the cluster.
kubectl get node -L disk,hardware
kubectl get pods -o wide

#restart a deployment 
kubectl rollout restart -n "namespace" deployment/"name of deployment"

#Delete all evitec pods from a namespace 
kubectl get pod -n "namespace" | grep Evicted | awk '{print $1}' | xargs kubectl delete pod -n  "namespace"
kubectl delete pod -n namespace $(kubectl get pod -n namespace | awk '/Evicted/ {print $1}') 

#Enter interactive mode on Ruby pod 
kubectl exec -it -n "namespace" "podname" -- bundle exec rails c  

#Enter interactive mode on mongoDB pod
kubectl exec -it nome-do-pod -n mongodb mongo

Logging
#Let's get the logs from the multicontainer pod...this will throw an error and ask us to define which container
kubectl logs $PODNAME


#But we need to specify which container inside the pods
kubectl logs $PODNAME -c container1
kubectl logs $PODNAME -c container2


#We can access all container logs which will dump each containers in sequence
kubectl logs $PODNAME --all-containers


#If we need to follow a log, we can do that...helpful in debugging real time issues
#This works for both single and multi-container pods
kubectl logs $PODNAME --all-containers --follow
ctrl+c


#For all pods matching the selector, get all the container logs and write it to stdout and then file
kubectl get pods --selector app=loggingdemo
kubectl logs --selector app=loggingdemo --all-containers 
kubectl logs --selector app=loggingdemo --all-containers  > allpods.txt


#Also helpful is tailing the bottom of a log...
#Here we're getting the last 5 log entries across all pods matching the selector
#You can do this for a single container or using a selector
kubectl logs --selector app=loggingdemo --all-containers --tail 5




#2 - Nodes
#Get key information and status about the kubelet, ensure that it's active/running and check out the log. 
#Also key information about it's configuration is available.
systemctl status kubelet.service


#If we want to examine it's log further, we use journalctl to access it's log from journald
# -u for which systemd unit. If using a pager, use f and b to for forward and back.
journalctl -u kubelet.service


#journalctl has search capabilities, but grep is likely easier
journalctl -u kubelet.service | grep -i ERROR


#Time bounding your searches can be helpful in finding issues add --no-pager for line wrapping
journalctl -u kubelet.service --since today --no-pager

#Events
#Show events for all objects in the cluster in the default namespace
#Look for the deployment creation and scaling operations from above...
#If you don't have any events since they are only around for an hour create a deployment to generate some
kubectl get events 


#It can be easier if the data is actually sorted...
#sort by isn't for just events, it can be used in most output
kubectl get events --sort-by='.metadata.creationTimestamp'
 

#Create a flawed deployment
kubectl create deployment nginx --image ngins


#We can filter the list of events using field selector
kubectl get events --field-selector type=Warning
kubectl get events --field-selector type=Warning,reason=Failed


#We can also monitor the events as they happen with watch
kubectl get events --watch &
kubectl scale deployment loggingdemo --replicas=5


#break out of the watch
fg
ctrl+c

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