Kubernetes User Handbook
This Kubernetes cheat sheet is prepared by our experts keeping in mind those learners who have started learning Kubernetes as a tool. This cheat sheet will be a handy reference for them when they start implementing what they have learned in real-life problems. In this Kubernetes cheat sheet, you get a quick reference to all the basics that you must know about Kubernetes.
Watch this video on Kubernetes Tutorial for Beginners:
You can also download the printable PDF of this Kubernetes cheat sheet
What is Kubernetes?
Kubernetes is an open-source platform used to automate deployment and to scale containers across clusters of hosts providing container-centric infrastructure.
- It is a container orchestrator.
- It can run a Linux container.
- Launches a container
- Maintains and monitors the container site
- Performs container-oriented networking
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Watch this video on Kubernetes Tutorial for Beginners:
The below image illustrates the architecture of Kubernetes. Let’s have a look at it.
Now, let’s discuss the key points of this architecture.
- Pod: Group of containers
- Label: Used to identify pods
- Kubelet: Container agents, responsible for maintaining the set of pods
- Proxy: The load balancer for pods, helping in distributing tasks across them
- Etcd: A metadata service
- CAdvisor: Used for monitoring resource usage and performance
- Replication controller: Manages pod replication
- Scheduler: Used for pod scheduling in worker nodes
- API server: Kubernetes API server
Now, let’s understand the roles master and worker nodes play in the Kubernetes architecture.
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- It is responsible for maintaining the desired state of the cluster we are working on.
- The term ‘master‘ indicates a set of processes that are used to manage a cluster.
- It contains Kubelet service info, API, scheduler, replication controller, and Kubernetes master.
Also called a ‘minion,’ a worker node contains the services necessary to run the pods that are managed by the master.
- Services it provides are Container Runtime, Kubelet, Kube-proxy, etc.
- It contains Kubelet, cAdvisor, Services, Pods, and Containers.
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Moving forward, let’s check out the important commands used in Kubernetes.
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For Pods and Container Introspection
|Kubectl get pods
||Lists all current pods
|Kubectl describe pod<name>
||Describes pod names
|Kubectl get rc
||Lists all replication controllers
|Kubectl get rc –namespace=”namespace”
||Lists replication controllers in a namespace
|Kubectl describe rc <name>
||Shows the replication controller name
|Kubectl get cvc
|Kubectl describe svc<name>
||Shows a service name
|Kubectl delete pod<name>
||Deletes a pod
|Kubectl get nodes -w
||Watches nodes continuously
|To execute the command on service by selecting a container
||Kubectl exec<service><commands>[-c< $container>]
|To get logs from the service for a container
||Kubectl logs -f<name>>[-c< $container>]
|To watch kubelet logs
||Watch -n 2 cat/var/log/kublet.log
|To show metrics for a node
||Kubectl top node
|To show metrics for a pod
||Kubectl top pod
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For Cluster Introspection
|To get version-related information
|To get cluster-related information
|To get configuration details
||Kubectl config g view
|To get information about a node
||Kubectl describe node<node>
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Some of the common objects used in Kubernetes are mentioned in the below table:
|cm= conf gmaps
||crd=custom resource definition
||csr= certificate signing requests
||ds= daemon sets
||hpa= horizontal pod autoscaling
||Netpol- network policies
|No = nodes
||pdb= pod distribution budgets
|Psp= pod security policies
||Pv= persistent volumes
||pvc= persistent volume claims
|quota= resource quotas
||rc= replication controllers
||rs= replica sets
||sa= service accounts
|sc= storage classes
||sts= stateful sets
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Other Quick Commands
Additionally, we do have some quick commands that are often very useful:
|To launch a pod with a name and an image
||Kubectl run<name> — image=<image-name>
|To create a service described in <manifest.yaml>
||Kubectl create -f <manifest.yaml>
|To scale the replication counter to count the number of instances
||Kubectl scale –replicas=<count>rc<name>
|To map the external port to the internal replication port
||Expose rc<name> –port=<external>–target-port=<internal>
|To stop all pods in <n>
||Kubectl drain<n>– delete-local-data–force–ignore-daemonset
|To create a namespace
||Kubectl create namespace <namespace>
|To allow the master node to run pods
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Features of Kubernetes
- Automated scheduling: It provides an advanced scheduler that helps launch containers on cluster nodes.
- Self-healing: Rescheduling, replacing, and restarting dead containers are possible.
- Automated rollouts and rollbacks: It supports rollback for systems in the case of failures and enables rollout and rollback for the desired state.
- Horizontal scaling: It can be scaled up and down as required and can be automated with respect to CPU usage.
- Service discovery and load balancing: It uses a unique IP and DNS name for containers that help in identifying them.
Download a Printable PDF of the Cheat Sheet
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