Kubectl Cheat Sheet

Hello and welcome! We have gathered the most commonly used commands in Kubernetes for you, all in one ready-to-use kubectl cheat sheet. In this "kubectl cheat sheet," we will walk you through step-by-step instructions on how to manage your Kubernetes cluster using the kubectl command-line tool.

What is kubectl?

Kubectl is the CLI tool for Kubernetes that allows you to interact with your clusters, create, manage, edit, and delete resources with ease. It communicates with the Kubernetes API server so you can monitor and control your applications.

How does kubectl work?

Kubectl operates by sending commands to the Kubernetes API server, which then carries out the requested operations within the cluster. When you execute a kubectl command, such as deploying an application or retrieving the status of resources, kubectl communicates with the API server over HTTP, transmitting your instructions. The API server processes these requests, updates the cluster's state in etcd (a distributed key-value store), and directs other components, like the scheduler or controller manager, to perform necessary actions to achieve the desired state. This interaction allows you to efficiently manage and monitor your Kubernetes resources from the command line. ​

In earlier versions of Kubernetes, kubectl utilized generators to create resource configurations based on specific inputs. These generators allowed users to specify the type of resource to create, such as a Pod, Deployment, or Job, by using the --generator flag. For example, kubectl run nginx --image=nginx --generator=run-pod/v1 would create a Pod resource. This approach enabled users to script and automate resource creation with predictable outcomes. However, it's important to note that the --generator flag was deprecated in Kubernetes v1.12 and removed in v1.18. As of v1.18, kubectl run is simplified to create only Pods, and the use of generators has been replaced by more explicit and declarative commands like kubectl create and kubectl apply

Now, let’s start:

Optional Flags

Kubectl provides optional flags that enhance command output and resource management. For example:

Output Formats:

JSON Output:

You can use the -o=json flag to format command output as JSON.

kubectl get pods -o=json

YAML Output:

You can use the -o=yaml flag to format command output as YAML.

kubectl get pods -o=yaml

Wide Output:

The -o=wide option provides detailed plain-text output (e.g., it displays the node name for pods).

kubectl get pods -o=wide

For more tailored outputs, kubectl offers the --custom-columns flag, allowing you to define specific columns to display. 

For example, to list pods with their names and the nodes they're running on:

kubectl get pods -o=custom-columns="POD NAME:.metadata.name,NODE:.spec.nodeName"

This command will output:

POD NAME           NODE
nginx-deployment-1  node-1
nginx-deployment-2  node-2

Namespace Specification:

By default, kubectl commands operate within the namespace defined by the current context. To target a specific namespace, you can use the -n or --namespace flag:

kubectl get pods -n 

To view resources across all namespaces, the -A or --all-namespaces flag is used:

kubectl get pods -A

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And to set a default namespace for the current context:

kubectl config set-context --current --namespace=ns_name

File Input:

The -f flag is used to specify a filename, directory, or URL when creating a resource.

kubectl create -f ./file_name

Label Filtering: 

You can use the -l flag to filter resources based on specific labels.

kubectl get pods -l name=label_name

Help Option:

To display help for kubectl commands, use the -h flag.

kubectl -h

Watch Mode:‍

You continuously monitor resource changes with the --watch (or -w) flag:

kubectl get pods -w

Sorting Output:‍

You can sort the output based on a specific field using the --sort-by flag:

kubectl get pods --sort-by=.metadata.name

kubectl Usage with Aliases

When you working with kubectl, it involves typing lengthy commands, which can be time-consuming and error-prone. To improve efficiency, many developers create aliases for frequently used commands.

Setting Up a Basic Alias

alias k=kubectl
echo 'alias k=kubectl' >> ~/.bashrc

This allows you to use k in place of kubectl. 

You can use the kubectl-aliases repository, which provides hundreds of pre-defined aliases, enabling quicker command execution.

For Cluster Management, Context and Configuration

Cluster Management means setting up, viewing, and modifying your cluster.

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Pod Management

Shortcode = po

A Pod is the smallest unit in Kubernetes, representing a single instance of a running process in your cluster. It can contain one or more containers that share storage and network resources.

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For ReplicaSets

Shortcode = rs

A ReplicaSet ensures a specified number of pod replicas are running. The main difference is that ReplicaSets support set-based label selectors.

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For Daemonsets

Shortcode = ds

A DaemonSet ensures that a specific pod runs on all (or some) nodes in the cluster. This is useful for tasks like running a monitoring agent on every node.

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For StatefulSets

Shortcode = sts

StatefulSets manage the deployment and scaling of pods, ensuring each has a unique, stable identity and persistent storage. This is important for stateful applications.

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For Namespace

Shortcode = ns

Namespaces provide a way to divide cluster resources between multiple users or applications.

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For Services

Shortcode = svc 

A Service defines a logical set of pods and a policy to access them. It enables communication between different parts of your application and can expose your application to external traffic.

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For Service Accounts

Shortcode = sa

A ServiceAccount provides an identity for processes running in a pod, allowing them to interact with the Kubernetes API securely.

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For Deployments

Shortcode = deploy

A Deployment provides declarative updates for pods and ReplicaSets. You can define the desired state of your application, and the Deployment controller changes the actual state to the desired state at a controlled rate.

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For Events

Shortcode = ev

Events are records of what happened in your cluster, such as pod creations, deletions, or errors.

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Logs

Logs are the output of your running applications and system components.

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For Secrets and Config Maps

Shortcode for ConfigMaps = cm

Secrets store sensitive information like passwords or keys, while ConfigMaps hold non-sensitive configuration data. Both allow you to decouple configuration artifacts from image content to keep your applications portable.

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For Node Management

Shortcode = no

A Node is a worker machine in Kubernetes.

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For Storage(PV, PVC)

Shortcode for Persistent Volume = pv

Shortcode for Persistent Volume Claim = pvc

PersistentVolumes are storage resources in your cluster, and PersistentVolumeClaims are requests for storage by users.

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For Copying Files and Directories

You can transfer files between your local system and a pod's container helping in debugging or data backup.

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For Output Verbosity and Debugging

Verbosity refers to the level of detail included in the logs generated by components like kubectl and kubelet. You can adjust the verbosity of kubectl commands.

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