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Containerization & Orchestration/Kubernetes/3-Commands.md
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Below is an improved version of your Kubernetes Command Reference. This revision enhances clarity, fixes typos, organizes related commands into logical sections, and standardizes formatting for readability.
---
# Kubernetes Command Reference # Kubernetes Command Reference
This document provides a reference for common `kubectl` commands used for managing Kubernetes clusters. Use the examples and explanations below to help manage nodes, namespaces, pods, deployments, and more. This document provides a concise reference for common `kubectl` commands used to manage Kubernetes clusters. Whether you’re managing nodes, namespaces, pods, deployments, or autoscaling, the examples below will help you perform everyday tasks with ease.
---
## Table of Contents ## Table of Contents
@@ -10,6 +14,9 @@ This document provides a reference for common `kubectl` commands used for managi
- [Table of Contents](#table-of-contents) - [Table of Contents](#table-of-contents)
- [General Commands](#general-commands) - [General Commands](#general-commands)
- [Node Management](#node-management) - [Node Management](#node-management)
- [Listing Nodes](#listing-nodes)
- [Labeling Nodes](#labeling-nodes)
- [Node Maintenance (Cordon/Drain)](#node-maintenance-cordondrain)
- [Namespace Management](#namespace-management) - [Namespace Management](#namespace-management)
- [Pod Management](#pod-management) - [Pod Management](#pod-management)
- [Listing Pods](#listing-pods) - [Listing Pods](#listing-pods)
@@ -18,9 +25,10 @@ This document provides a reference for common `kubectl` commands used for managi
- [API Resources and Documentation](#api-resources-and-documentation) - [API Resources and Documentation](#api-resources-and-documentation)
- [Logs and Pod Information](#logs-and-pod-information) - [Logs and Pod Information](#logs-and-pod-information)
- [Applying YAML Files](#applying-yaml-files) - [Applying YAML Files](#applying-yaml-files)
- [Managing Nodes and Labels](#managing-nodes-and-labels)
- [Viewing Cluster Resources](#viewing-cluster-resources) - [Viewing Cluster Resources](#viewing-cluster-resources)
- [ReplicaSet and Deployment Management](#replicaset-and-deployment-management) - [ReplicaSet and Deployment Management](#replicaset-and-deployment-management)
- [Scaling and Rollouts](#scaling-and-rollouts)
- [Autoscaling](#autoscaling)
- [Additional Information](#additional-information) - [Additional Information](#additional-information)
--- ---
@@ -29,6 +37,8 @@ This document provides a reference for common `kubectl` commands used for managi
- **List API Resources** - **List API Resources**
Display all available API resources along with their short names:
```bash ```bash
kubectl api-resources kubectl api-resources
``` ```
@@ -37,34 +47,65 @@ This document provides a reference for common `kubectl` commands used for managi
## Node Management ## Node Management
- **Show all nodes** ### Listing Nodes
- **Show All Nodes**
```bash ```bash
kubectl get node kubectl get nodes
``` ```
- **Set a label on a node** ### Labeling Nodes
- **Set a Custom Label on a Node**
```bash ```bash
kubectl label nodes <node-name> kubernetes.io/<label-key>=<label-value> kubectl label node <node-name> kubernetes.io/<label-key>=<label-value>
``` ```
> **Note:** Replace `<node-name>`, `<label-key>`, and `<label-value>` with your desired values.
### Node Maintenance (Cordon/Drain)
- **Cordon a Node**
Prevent new pods from being scheduled on the node.
```bash
kubectl cordon <node-name>
```
- **Uncordon a Node**
Mark the node as schedulable again.
```bash
kubectl uncordon <node-name>
```
- **Drain a Node**
Evict all pods from the node (excluding those managed by DaemonSets).
```bash
kubectl drain <node-name> --ignore-daemonsets --delete-local-data
```
> **Warning:** Draining a node will evict running pods. Ensure this action is planned to avoid service disruption.
--- ---
## Namespace Management ## Namespace Management
- **List all namespaces** - **List All Namespaces**
```bash ```bash
kubectl get namespaces kubectl get namespaces
# or the abbreviated version: # Or use the shorthand:
kubectl get ns kubectl get ns
``` ```
- **Create a custom namespace** - **Create a New Namespace**
```bash ```bash
kubectl create ns <namespace-name> kubectl create namespace <namespace-name>
``` ```
--- ---
@@ -73,104 +114,103 @@ This document provides a reference for common `kubectl` commands used for managi
### Listing Pods ### Listing Pods
- **List pods in the default namespace** - **List Pods in the Default Namespace**
```bash ```bash
kubectl get pod kubectl get pods
``` ```
- **List pods with detailed information (wide output) in the default namespace** - **List Pods with Detailed Information (Wide Output)**
```bash ```bash
kubectl get pod -o wide kubectl get pods -o wide
``` ```
- **List pods with detailed information in a specific namespace** - **List Pods in a Specific Namespace**
```bash ```bash
kubectl get pod -o wide -n <namespace-name> kubectl get pods -o wide -n <namespace-name>
``` ```
### Running a Pod ### Running a Pod
- **Run a new pod** > **Note:** While `kubectl run` is a versatile command, note that in recent Kubernetes versions it is primarily used for running single pods (not deployments). For more complex configurations, consider using YAML manifests.
Use the following command structure to run a pod with various options: - **Basic Example:**
```bash ```bash
kubectl run <pod-name> <switch> { kubectl run <pod-name> --image=<image-name> --port=<port-number> -n <namespace-name>
--image=<image-name>, # Container image to use
--port=<port-number>, # Port that the container exposes
-n <namespace-name>, # Namespace in which to run the pod
--env="KEY=VALUE", # Environment variables for the container
--command, # Treat the following arguments as the command
--replicas=<number>, # Number of pod replicas to create
--labels="key=value,key2=value2", # Labels to assign to the pod(s)
--dry-run=client, # Print the object without creating it
--restart=<Always|OnFailure|Never>, # Pod restart policy
--overrides='<json>', # JSON override for the generated object
--image-pull-policy=<policy>, # Image pull policy (Always, IfNotPresent, Never)
--limits=cpu=<cpu>,memory=<memory>, # Resource limits for the container
--requests=cpu=<cpu>,memory=<memory> # Resource requests for the container
}
``` ```
- **Example:** - **Advanced Example with Multiple Options:**
```bash ```bash
kubectl run mypod --image=nginx --port=80 -n mynamespace \ kubectl run mypod --image=nginx --port=80 -n mynamespace \
--env="ENV_VAR_NAME=VALUE" --command -- nginx -g "daemon off;" \ --env="ENV_VAR_NAME=VALUE" --command -- nginx -g "daemon off;" \
--replicas=3 --labels="app=myapp,env=prod" --dry-run=client \ --restart=Always --dry-run=client \
--restart=Always --overrides='{"spec": {"containers": [{"name": "nginx", "image": "nginx"}]}}' \ --labels="app=myapp,env=prod" \
--image-pull-policy=IfNotPresent --limits=cpu=100m,memory=256Mi \ --limits=cpu=100m,memory=256Mi --requests=cpu=50m,memory=128Mi
--requests=cpu=50m,memory=128Mi ```
```
**Common Options Explained:**
- `--image`: Container image to use.
- `--port`: Port exposed by the container.
- `-n` or `--namespace`: Namespace in which to run the pod.
- `--env`: Set environment variables.
- `--command`: Treat the following arguments as the command to run.
- `--restart`: Pod restart policy (`Always`, `OnFailure`, or `Never`).
- `--labels`: Assign labels to the pod.
- `--dry-run`: Validate the command without creating the pod.
- `--limits` and `--requests`: Define resource limits and requests for the container.
### Deleting a Pod ### Deleting a Pod
- **Delete a pod in a custom namespace** - **Delete a Pod in a Specific Namespace**
```bash ```bash
kubectl delete pod -n <namespace-name> <pod-name> kubectl delete pod <pod-name> -n <namespace-name>
``` ```
--- ---
## API Resources and Documentation ## API Resources and Documentation
- **Get documentation for an API resource** - **Get Detailed Documentation for an API Resource**
```bash ```bash
kubectl explain <api-resource-name> kubectl explain <api-resource-name>
``` ```
- *Example:* *Example:*
```bash ```bash
kubectl explain pod kubectl explain pod
``` ```
--- ---
## Logs and Pod Information ## Logs and Pod Information
- **Stream logs for a running pod** - **Stream Logs for a Running Pod**
```bash ```bash
kubectl logs -f -n <namespace-name> <pod-name> kubectl logs -f -n <namespace-name> <pod-name>
``` ```
- **Get detailed state and log information for a pod** - **Get Detailed Information About a Pod**
```bash ```bash
kubectl describe pod -n <namespace-name> <pod-name> kubectl describe pod <pod-name> -n <namespace-name>
``` ```
--- ---
## Applying YAML Files ## Applying YAML Files
- **Apply configuration from a YAML file to a specific namespace** - **Apply a Configuration from a YAML File**
Apply a YAML configuration to a specific namespace:
```bash ```bash
kubectl apply -f <yaml-file> -n <namespace-name> kubectl apply -f <yaml-file> -n <namespace-name>
@@ -178,59 +218,65 @@ This document provides a reference for common `kubectl` commands used for managi
--- ---
## Managing Nodes and Labels
- **Label a node with a custom key-value pair**
```bash
kubectl label nodes <node-name> kubernetes.io/<label-key>=<label-value>
```
---
## Viewing Cluster Resources ## Viewing Cluster Resources
- **Display all resources loaded in a namespace** - **Display All Resources in a Namespace**
```bash ```bash
kubectl get all -n <namespace-name> kubectl get all -n <namespace-name>
``` ```
- **Display replica sets, pods, and deployments in a specific namespace** - **Display ReplicaSets, Pods, and Deployments in a Specific Namespace**
```bash ```bash
kubectl get rs,pod,deployment -n <namespace-name> kubectl get rs,pods,deployments -n <namespace-name>
``` ```
--- ---
## ReplicaSet and Deployment Management ## ReplicaSet and Deployment Management
### Scaling and Rollouts
- **Scale a ReplicaSet** - **Scale a ReplicaSet**
```bash ```bash
kubectl scale rs <replicaset-name> -n <namespace-name> --replicas=<count> kubectl scale rs <replicaset-name> --replicas=<count> -n <namespace-name>
``` ```
- **View rollout history of a deployment** - **View Rollout History of a Deployment**
```bash ```bash
kubectl rollout history deployment -n <namespace-name> <deployment-name> kubectl rollout history deployment <deployment-name> -n <namespace-name>
``` ```
- **View details of a specific revision in a deployment's rollout history** - **View Details of a Specific Revision**
```bash ```bash
kubectl rollout history deployment -n <namespace-name> <deployment-name> --revision <number> kubectl rollout history deployment <deployment-name> -n <namespace-name> --revision=<number>
``` ```
- **Roll back a deployment to a specific revision** - **Roll Back a Deployment to a Specific Revision**
```bash ```bash
kubectl rollout undo deployment -n <namespace-name> <deployment-name> --to-revision=<number> kubectl rollout undo deployment <deployment-name> -n <namespace-name> --to-revision=<number>
``` ```
> **Note:** The command for rolling back to a specific revision is `kubectl rollout undo` rather than using `--to-revision` with `kubectl rollout history`. ### Autoscaling
- **Autoscale a Deployment**
Automatically scale a deployment based on CPU utilization:
```bash
kubectl autoscale deployment <deployment-name> -n <namespace-name> --cpu-percent=<target-cpu-percentage> --min=<min-pods> --max=<max-pods>
```
- **View Horizontal Pod Autoscalers (HPA)**
```bash
kubectl get hpa -n <namespace-name>
```
--- ---
@@ -238,6 +284,4 @@ This document provides a reference for common `kubectl` commands used for managi
- **Static Manifest Files** - **Static Manifest Files**
All YAML files located under `/etc/kubernetes/manifests/` are automatically loaded after a server reboot. Any YAML files placed in `/etc/kubernetes/manifests/` are automatically loaded when the kubelet starts (for example, after a server reboot).
---