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Collection of the resources sequentially for learning kubernetes including necessary hands-on.

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configmap
configmap
 
 
ingress
ingress
 
 
jobs
jobs
 
 
rbac
rbac
 
 
secret
secret
 
 
storage
storage
 
 
.gitignore
.gitignore
 
 
README.md
README.md
 
 
daemonset.yaml
daemonset.yaml
 
 
ephemeral-containers.yaml
ephemeral-containers.yaml
 
 
init-containers.yaml
init-containers.yaml
 
 
minikube_deployment.yaml
minikube_deployment.yaml
 
 
nginx-deployment-result.yaml
nginx-deployment-result.yaml
 
 
nginx-deployment.yaml
nginx-deployment.yaml
 
 
nginx-service.yaml
nginx-service.yaml
 
 
pod-for-configmap-as-volume.yaml
pod-for-configmap-as-volume.yaml
 
 
pod-for-configmap.yaml
pod-for-configmap.yaml
 
 
pod-for-pv-and-pvc-hostPath.yaml
pod-for-pv-and-pvc-hostPath.yaml
 
 
pod-for-secret-as-env.yaml
pod-for-secret-as-env.yaml
 
 
pod-for-secret-as-volume.yaml
pod-for-secret-as-volume.yaml
 
 
pod-for-volume.yaml
pod-for-volume.yaml
 
 
pod-with-lifecycle-hooks.yaml
pod-with-lifecycle-hooks.yaml
 
 
pv-using-hostPath.yaml
pv-using-hostPath.yaml
 
 
pv-using-local-path.yaml
pv-using-local-path.yaml
 
 
pvc-for-pv-using-hostPath.yaml
pvc-for-pv-using-hostPath.yaml
 
 
service-externalIP.yaml
service-externalIP.yaml
 
 
service-loadbalancer.yaml
service-loadbalancer.yaml
 
 
service-multiport.yaml
service-multiport.yaml
 
 
services-for-init-containers.yaml
services-for-init-containers.yaml
 
 
statefulset-with-volume.yaml
statefulset-with-volume.yaml
 
 
statefulset.yaml
statefulset.yaml
 
 

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kubernetes-stuffs

Description

Collection of the resources sequentially for learning kubernetes.

Kubernetes

Kubernetes is a container orchestration tool. It offers three most important facilities :

  • High Availability or No Downtime
  • Scalability or High Performance
  • Disaster Recovery - Backup and Restore

Instruction for using this repo

At first fork this repo, then go through the resources sequentially as they are given. Everytime when you complete a tutorial tick the checkbox by giving x in the - [ ] eg. - [x] and then push that to your forked repo, by this way you can track your progress.

Cheat Sheet of Kubernetes

Installation

  • Install minikube
    • Minikube is a lightweight Kubernetes implementation that creates a VM on your local machine and deploys a simple cluster containing only one node.
  • Install kubectl
    • The kubectl command line tool lets you control Kubernetes clusters. kubectl is kubernetes command line interface which uses the kubernetes API to interact with the cluster.

Commands

Step #01: Create a kubernetes cluster

Commands Uses
minikube version Check that minikube is properly installed
minikube start To run kubernetes cluster. You now have a running Kubernetes cluster. Minikube started a virtual machine for you, and a Kubernetes cluster is now running in that VM.
minikube ip To see the IP of the VM
minikube dashboard To see the dashboard
kubectl version To check if kubectl is installed properly. kubectl is configured and we can see both the version of the client and as well as the server. The client version is the kubectl version; the server version is the Kubernetes version installed on the master. You can also see details about the build.
kubectl cluster-info To view the cluster details
kubectl get nodes To view the nodes in the cluster. This command shows all nodes that can be used to host our applications. Now we have only one node, and we can see that its status is ready (it is ready to accept applications for deployment).
kubectl get all To list all applications and services on the cluster
minikube stop To halt the cluster
minikube pause Pause kubernetes without impacting deployed applications
minikube delete --all To delete all of the minikube clusters
minikube delete To delete the minikube VM
minikube addons list To see the list of the currently supported addons in minikube
minikube addons enable <addons_name> To enable an addon
minikube addons disable <addons_name> To disable an addon

Step #02: Deploying an App on kubernetes using kubectl

Commands Uses
kubectl create deployment <deployment_name> --image=<app_image_location> To deploy the app on kubernetes. Include the full repository url for images hosted outside Docker hub but for images from docker hube just give the repo/image_name:tag
kubectl create deployment restapi --image=shahincsejnu/httpapiserver:v1.0.7 To deploy httpapiserver:v1.0.7 image on kubernetes from dockerhub with username shahincsejnu
kubectl get deployment To see the list of all your deployments
kubectl proxy Pods that are running inside Kubernetes are running on a private, isolated network. By default they are visible from other pods and services within the same kubernetes cluster, but not outside that network. When we use kubectl, we're interacting through an API endpoint to communicate with our application. We now have a connection between our host (the online terminal) and the Kubernetes cluster. The proxy enables direct access to the API from these terminals.
curl http://localhost:8001/ When the kube-proxy is running to see all the endpoints in kube api server
curl http://localhost:8001/version To request an endpoint of the api server, give your desired endpoint instead version

Step #03: Explore the App : Viewing Pods and Nodes

Commands Uses
kubectl get <nodes/pods/deployments/services> To see the List of all related(nodes/pods/deployments) resources
kubectl describe <nodes/pods/deployments> To show detailed information about a resource
kubectl logs $POD_NAME To print the logs from a container in a pod. Note: We don’t need to specify the container name, because we only have one container inside the pod.
kubectl exec To execute a command on a container in a pod
kubectl exec $POD_NAME env To view the list of environment variables of the pod
kubectl exec -ti $POD_NAME <bash or sh> To start a bash session in the pod's container
kubectl exec -it <pod_name> -c <container_name> <bash or sh> To exec a specific container of a pod, if the container name does not provide then it will enter the deault continaer which is the first container of the pod
exit To close your container connection, from inside the container

Step #04: Expose you app publicly : using a service to expose your app

Commands Uses
kubectl get services To see the list of services. Note that, Although each Pod has a unique IP address, those IPs are not exposed outside the cluster without a Service. Services allow your applications to receive traffic.
kubectl deployment/<deployment_name> --type="NodePort" --port 8080 o create a new service and expose it to external traffic we’ll use the expose command with NodePort as parameter (minikube does not support the LoadBalancer option yet).
kubectl describe services/<service_name> To find out what port was opened externally (by the NodePort option)
curl $(minikube ip):$NODE_PORT Now we can test that the app is exposed outside of the cluster using curl, the IP of the Node and the externally exposed port:
curl $(minikube ip):$NODE_PORT/api/articles
curl -X GET --user admin:admin $(minikube ip):$NODE_PORT/api/login
kubectl describe deployment The Deployment created automatically a label for our Pod. With describe deployment command you can see the name of the label:
kubectl get pods -l <label_values>
kubectl get pods -l run=kubernetes-bootcamp Let’s use this label to query our list of Pods. We’ll use the kubectl get pods command with -l as a parameter, followed by the label values:
kubectl get services -l run=kubernetes-bootcamp we can do same to list the existing services
kubectl label pod $POD_NAME <new_label> To apply a new label we use the label command followed by the object type, object name and the new label. This will apply a new label to our Pod (we pinned the application version to the Pod), and we can check it with the describe pod command:
kubectl describe pods $POD_NAME We see here that the label is attached now to our Pod. And we can query now the list of pods using the new label:
kubectl get pods -l <new_lable>
kubectl delete service -l <label_name> To delete Services you can use the delete service command. Labels can be used also here:
kubectl get services Confirm that service is gone
curl $(minikube ip):$NODE_PORT This confirms that our Service was removed. To confirm that route is not exposed anymore you can curl the previously exposed IP and port: We see here that the application is up. This is because the Deployment is managing the application. To shut down the application, you would need to delete the Deployment as well.
kubectl exec -ti $POD_NAME curl localhost:8080 You can confirm that the app is still running with a curl inside the pod:

Step #05: Scale your app : Running multiple instances of your app

Command Uses
kubectl get rs To see the ReplicaSet created by the Deployment. Notice that the name of the ReplicaSet is always formatted as [DEPLOYMENT-NAME]-[RANDOM-STRING]. The random string is randomly generated and uses the pod-template-hash as a seed.
kubectl scale deployments/<deployment_name> --replicas=4 To scale up we'll use the kubectl scale command, followed by the deployment type, name and desired number of instances
kubectl get deployments Now see the deployment list
kubectl get pods -o wide Next, let’s check if the number of Pods changed. There are 4 Pods now, with different IP addresses.
kubectl describe deployments/<deployment_name> The change was registered in the Deployment events log. To check that, use the describe command
kubectl describe services/<service_name> To find out the exposed IP and Port we can use the describe service
curl $(minikube ip):$NODE_PORT Next, we’ll do a curl to the exposed IP and port. Execute the command multiple times. We hit a different Pod with every request. This demonstrates that the load-balancing is working.
kubectl scale deployments/<deployment_name> --replicas=2 To scale down the Service to 2 replicas, run again the scale command.
kubectl get deployments List the Deployments to check if the change was applied with the get deployments command.
kubectl get pods -o wide The number of replicas decreased to 2. List the number of Pods, with get pods: This confirms that 2 Pods were terminated.

Step #06: Update your app : Performing a Rolling update

Command Uses
kubectl get deployments To list all of the deployments
kubectl get pods To list the running pods
kubectl describe pods To view the current image version of the app, look at the image field
kubectl set image deployments/<deployment_name> <new_image_version> To update the image of the application to version 2, use the set image command, followed by the deployment name and the new image version. The command notified the Deployment to use a different image for your app and initiated a rolling update.
kubectl get pods Check the status of the new Pods, and view the old one.
kubectl describe services/<service_name> Verify and update. First, let’s check that the App is running. To find out the exposed IP and Port we can use describe service.
curl $(minikube ip):$NODE_PORT we’ll do a curl to the the exposed IP and port. We hit a different Pod with every request and we see that all Pods are running the latest version (v2).
kubectl rollout status deployments/<deployment_name> The update can be confirmed also by running a rollout status command.
kubectl describe pods To view the current image version of the app, run a describe command against the Pods. We run now version 2 of the app (look at the image field).
kubectl rollout undo deployments/<deployment_name> If there is no image in the repository that we deployed then we do roll back. The rollout command reverted the deployment to the previous known state (v2 of the image). Updates are versioned and you can revert to any previously know state of a Deployment.
kubectl get pods List again the pods
kubectl describe pods Check again the image deployed on them

Some intuition

  • docker ps to see the container where minikube image is running
  • docker exec -it <minikube_container_id> to enter the VM/container of the min
  • again do docker ps to see the all docker containers that are running on minikube container
  • now you can enter any specific container by doing exec and see the things.
  • kubectl describe pods <pod_name> for seeing the specific pod information
  • watch -n 1 kubectl get pods to see the pods with updating every other second
  • kubectl get pod <pod_name> -o yaml to see the details of pod configuration yaml format
  • kubectl get <resource_name> --v=10 for seeing the verbose (the whole things of http request)
  • kubectl get --raw <endpoint_of_http_call> for doing the raw call

Deleting an application/deployment with kubectl

  • kubectl get all
  • kubectl delete <deployment_name> <deployment_related_service_name>
  • or kubectl delete deployment deployment_name and then kubectl delete servcie servcie_name

kubectl completion for fish shell

  • mkdir -p ~/.config/fish/completions
  • cd ~/.config/fish
  • git clone https://github.com/evanlucas/fish-kubectl-completions
  • ln -s ../fish-kubectl-completions/completions/kubectl.fish completions/

kubectl port-forward : Forward a local port to a port on the Pod

  • Kubectl 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 adjust your services locally without the need to expose them beforehand.
    • kubectl port-forward pod_name pod_port:local_port

kubernetes tasks using kind

Some important commands of kind

  • cat ~/.kube/config to print the configuration of kubernetes for the clusters
  • kubectl config view to see the clusters and their server and also current cluster
  • kubectl config use-context kind-<cluster_name> to switch to <cluster_name> cluster
  • kubectl cluster-info --context kind-<cluster_name> to see the <cluster_name> cluster info
  • kind create cluster to create a new cluster and also current cluster become this new cluster
  • kubectl get pods --all-namespaces -o wide
  • kubectl get node -o wide to see the details of node with node ip, for using curl -X GET --user admin:admin http://<node_internal_ip>:<node_exposed_port>/api/login
  • kubectl get deployment/pod/service <deployment/pod/service_name> -o yaml to see the deployment/pod/service configuration of <deployment/pod/service_name> in yaml format
  • kubectl get deployment/pod/service <deployment/pod/service_name> -o yaml > <file_name>.yaml to see the deployment/pod/service configuration of <deployment/pod/service_name> in yaml format and save it to a yaml file in the current directory.
  • kubectl get pods --show-lables to show the pods with their label names

deployment and service through yaml

  • kubectl apply -f <deployment/service_file_name>.yaml to create a deployment/service
  • kubectl apply -k <directory/folder_where_the_yaml_exists> to create all the yaml in one command

K8s API

There are multiple api in k8s and many more are coming over the time.

  • kubectl api-resources To get the list of api resources, to know which resources are in the under of which API
  • kubectl api-versions Will tell you which version is to use to create specific resource
  • kubectl explain <name_of_an_api_resources> explain exactly what you want to have in the YAML file to create <name_of_an_api_resources>

Resources

Kubenetes Concepts

  1. Videos

  2. Topic wise Tutorials

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Collection of the resources sequentially for learning kubernetes including necessary hands-on.

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kubernetes kubernetes-cluster kubectl yaml-format

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