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:
Architecture/Interaction
The below image illustrates the architecture of Kubernetes. Let’s have a look at it.
Key Concepts
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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Master Node
- 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.
Worker Nodes/Minions
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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Kubectl Commands
For Pods and Container Introspection
| Command |
Function |
| 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 |
Lists services |
| Kubectl describe svc<name> |
Shows a service name |
| Kubectl delete pod<name> |
Deletes a pod |
| Kubectl get nodes -w |
Watches nodes continuously |
For Debugging
| Function |
Command |
| 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
| Function |
Command |
| To get version-related information |
Kubectl version |
| To get cluster-related information |
Kubectl cluster-info |
| To get configuration details |
Kubectl config g view |
| To get information about a node |
Kubectl describe node<node> |
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Objects
Some of the common objects used in Kubernetes are mentioned in the below table:
| All |
clusterrolebindings |
clusterroles |
| cm= conf gmaps |
controllerrevisions |
crd=custom resource definition |
| Cronjobs |
cs=component statuses |
csr= certificate signing requests |
| Deploy=deployments |
ds= daemon sets |
ep=end points |
| ev= events |
hpa= horizontal pod autoscaling |
ing= ingress |
| jobs |
limits=limit ranges |
Netpol- network policies |
| No = nodes |
ns= namespaces |
pdb= pod distribution budgets |
| po= pods |
Pod preset |
Pod templates |
| Psp= pod security policies |
Pv= persistent volumes |
pvc= persistent volume claims |
| quota= resource quotas |
rc= replication controllers |
Role bindings |
| roles |
rs= replica sets |
sa= service accounts |
| sc= storage classes |
secrets |
sts= stateful sets |
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Other Quick Commands
Additionally, we do have some quick commands that are often very useful:
| Function |
Command |
| 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 |
Kubectltaintnodes –all-node-role.kuernetes.io/master- |
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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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