Complete DevOps Cheatsheet

Comprehensive DevOps reference covering Docker, Kubernetes, Git, CI/CD, Linux, AWS, Terraform, Ansible, Jenkins, and monitoring tools. Essential commands and best practices for DevOps engineers.

DevOps

Docker - Container Basics

Docker container lifecycle and basic operations

docker

Docker: Platform for developing, shipping, and running applications in containers

Container: Lightweight, standalone executable package with everything needed to run software

Image: Template for creating containers

bash

# Container Lifecycle
docker run nginx              # Create and start container
docker run -d nginx           # Detached mode
docker run -it ubuntu bash    # Interactive terminal
docker run --name web nginx   # Named container
docker run -p 8080:80 nginx   # Port mapping

# Container Management
docker ps                     # Running containers
docker ps -a                  # All containers
docker stop container_id      # Stop container
docker start container_id     # Start container
docker restart container_id   # Restart container
docker rm container_id        # Remove container
docker rm -f container_id     # Force remove

bash

# Container Inspection
docker logs container_id      # View logs
docker logs -f container_id   # Follow logs
docker exec -it container_id bash  # Execute command
docker inspect container_id   # Detailed info
docker stats                  # Resource usage
docker top container_id       # Running processes

Docker - Images

Building, managing, and optimizing Docker images

docker

Dockerfile: Text file with instructions to build Docker image

Layer: Each instruction in Dockerfile creates a layer

Registry: Storage and distribution system for Docker images (Docker Hub, ECR)

bash

# Image Operations
docker images                 # List images
docker pull nginx:latest      # Pull image
docker push user/image:tag    # Push to registry
docker build -t myapp:1.0 .   # Build image
docker tag source target      # Tag image
docker rmi image_id           # Remove image
docker image prune            # Remove unused images

dockerfile

# Sample Dockerfile
FROM node:16-alpine
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
EXPOSE 3000
CMD ["npm", "start"]

# Multi-stage Build
FROM node:16 AS builder
WORKDIR /app
COPY . .
RUN npm install && npm run build

FROM nginx:alpine
COPY --from=builder /app/dist /usr/share/nginx/html

Docker - Networks & Volumes

Container networking and data persistence

docker

bash

# Docker Networks
docker network ls                    # List networks
docker network create mynetwork      # Create network
docker network inspect mynetwork     # Network details
docker run --network mynetwork nginx # Connect to network

# Network Types
# bridge: Default, isolated network
# host: Use host's network
# none: No networking

# Docker Volumes
docker volume ls                     # List volumes
docker volume create myvolume        # Create volume
docker volume inspect myvolume       # Volume details
docker run -v myvolume:/data nginx   # Mount volume
docker run -v $(pwd):/app nginx      # Bind mount

# Volume Management
docker volume prune                  # Remove unused volumes
docker volume rm myvolume            # Remove volume

Docker Compose

Multi-container application management

docker

Docker Compose: Tool for defining and running multi-container applications

docker-compose.yml: YAML file defining services, networks, and volumes

bash

# Docker Compose Commands
docker-compose up                    # Start services
docker-compose up -d                 # Detached mode
docker-compose down                  # Stop and remove
docker-compose ps                    # List services
docker-compose logs                  # View logs
docker-compose logs -f servicename   # Follow logs
docker-compose exec service bash     # Execute command
docker-compose build                 # Build images
docker-compose restart               # Restart services

yaml

# Sample docker-compose.yml
version: '3.8'
services:
  web:
    build: .
    ports:
      - "3000:3000"
    environment:
      - NODE_ENV=production
    depends_on:
      - db
    volumes:
      - ./app:/app
  
  db:
    image: postgres:14
    environment:
      POSTGRES_PASSWORD: secret
    volumes:
      - pgdata:/var/lib/postgresql/data

volumes:
  pgdata:

Kubernetes - Cluster Basics

Kubernetes cluster operations and namespace management

kubernetes

Kubernetes (K8s): Container orchestration platform for automating deployment, scaling, and management

kubectl: Command-line tool for Kubernetes

Namespace: Virtual cluster for resource isolation

bash

# Cluster Information
kubectl cluster-info              # Cluster details
kubectl get nodes                 # List nodes
kubectl describe node node1       # Node details
kubectl version                   # Kubernetes version
kubectl api-resources             # Available resources

bash

# Namespace Operations
kubectl get namespaces            # List namespaces
kubectl create namespace dev      # Create namespace
kubectl delete namespace dev      # Delete namespace
kubectl config set-context --current --namespace=dev
kubectl get all -n dev            # All resources in namespace

Kubernetes - Pods & Deployments

Managing pods and deployments in Kubernetes

kubernetes

Pod: Smallest deployable unit, contains one or more containers

Deployment: Manages replica sets and provides declarative updates

ReplicaSet: Ensures specified number of pod replicas are running

bash

# Pod Operations
kubectl get pods                  # List pods
kubectl get pods -A               # All namespaces
kubectl get pods -o wide          # Detailed view
kubectl describe pod mypod        # Pod details
kubectl logs mypod                # Pod logs
kubectl logs -f mypod             # Follow logs
kubectl logs mypod -c container   # Specific container
kubectl exec -it mypod -- bash    # Execute command
kubectl delete pod mypod          # Delete pod

bash

# Deployment Management
kubectl get deployments           # List deployments
kubectl create deployment nginx --image=nginx
kubectl scale deployment nginx --replicas=3
kubectl set image deployment/nginx nginx=nginx:1.19
kubectl rollout status deployment/nginx
kubectl rollout history deployment/nginx
kubectl rollout undo deployment/nginx
kubectl delete deployment nginx

Kubernetes - Services & ConfigMaps

Networking and configuration management

kubernetes

Service: Exposes pods to network traffic (ClusterIP, NodePort, LoadBalancer)

ConfigMap: Store configuration data as key-value pairs

Secret: Store sensitive data (passwords, tokens)

bash

# Service Operations
kubectl get services              # List services
kubectl expose deployment nginx --port=80 --type=LoadBalancer
kubectl describe service nginx    # Service details
kubectl delete service nginx

# Service Types
# ClusterIP: Internal cluster access
# NodePort: External access via node port
# LoadBalancer: Cloud load balancer

bash

# ConfigMap & Secrets
kubectl create configmap app-config --from-literal=key=value
kubectl create configmap app-config --from-file=config.properties
kubectl get configmaps
kubectl describe configmap app-config

kubectl create secret generic db-secret --from-literal=password=secret
kubectl get secrets
kubectl describe secret db-secret

Kubernetes - YAML Manifests

Declarative resource management with YAML

kubernetes

Declarative: Define desired state in YAML files

Imperative: Direct commands to make changes

Best Practice: Use declarative approach for production

bash

# Resource Management
kubectl create -f file.yaml       # Create resource
kubectl apply -f file.yaml        # Apply/update resource
kubectl delete -f file.yaml       # Delete resource
kubectl apply -f ./directory/     # Apply all in directory
kubectl get -f file.yaml          # Get resource status

yaml

# Sample Deployment YAML
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.19
        ports:
        - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  selector:
    app: nginx
  ports:
  - port: 80
    targetPort: 80
  type: LoadBalancer

Git - Basic Operations

Version control fundamentals with Git

git

Git: Distributed version control system

Repository: Project directory tracked by Git

Commit: Snapshot of project at specific time

bash

# Repository Setup
git init                          # Initialize repository
git clone url                     # Clone repository
git config --global user.name "Name"
git config --global user.email "email@example.com"

# Basic Workflow
git status                        # Check status
git add file.txt                  # Stage file
git add .                         # Stage all changes
git commit -m "message"           # Commit changes
git commit -am "message"          # Add and commit

bash

# Viewing History
git log                           # Commit history
git log --oneline                 # Compact view
git log --graph --all             # Visual graph
git show commit_hash              # Show commit
git diff                          # Unstaged changes
git diff --staged                 # Staged changes

Git - Branching & Merging

Branch management and merge strategies

git

bash

# Branch Operations
git branch                        # List branches
git branch feature                # Create branch
git checkout feature              # Switch branch
git checkout -b feature           # Create and switch
git branch -d feature             # Delete branch
git branch -D feature             # Force delete

# Merging
git merge feature                 # Merge branch
git merge --no-ff feature         # No fast-forward
git rebase main                   # Rebase onto main

# Remote Branches
git fetch                         # Fetch remote changes
git pull                          # Fetch and merge
git push origin main              # Push to remote
git push -u origin feature        # Push new branch
git push --delete origin feature  # Delete remote branch

Git - Advanced Operations

Stashing, cherry-picking, and history rewriting

git

bash

# Stashing Changes
git stash                         # Stash changes
git stash list                    # List stashes
git stash apply                   # Apply latest stash
git stash pop                     # Apply and remove
git stash drop                    # Delete stash

# Undoing Changes
git reset HEAD file.txt           # Unstage file
git checkout -- file.txt          # Discard changes
git reset --soft HEAD~1           # Undo commit, keep changes
git reset --hard HEAD~1           # Undo commit, discard changes
git revert commit_hash            # Create reverse commit

# Cherry-picking & Tags
git cherry-pick commit_hash       # Apply specific commit
git tag v1.0.0                    # Create tag
git tag -a v1.0.0 -m "message"    # Annotated tag
git push origin v1.0.0            # Push tag

Linux - File Operations

Essential Linux commands for file management

linux

bash

# Navigation & Listing
ls                                # List files
ls -la                            # Detailed list with hidden
pwd                               # Current directory
cd /path/to/dir                   # Change directory
cd ..                             # Parent directory

# File Operations
touch file.txt                    # Create file
mkdir directory                   # Create directory
mkdir -p path/to/dir              # Create nested directories
cp source dest                    # Copy file
cp -r source dest                 # Copy directory
mv source dest                    # Move/rename
rm file.txt                       # Remove file
rm -rf directory                  # Remove directory recursively

# File Viewing
cat file.txt                      # Display content
less file.txt                     # Paginated view
head -n 10 file.txt               # First 10 lines
tail -n 10 file.txt               # Last 10 lines
tail -f file.txt                  # Follow file updates

Linux - Permissions & Users

User management and file permissions

linux

Permissions: Read (r=4), Write (w=2), Execute (x=1)

Format: Owner-Group-Others (e.g., 755 = rwxr-xr-x)

bash

# File Permissions
chmod 755 file.txt                # Change permissions
chmod +x script.sh                # Add execute permission
chmod -R 644 directory            # Recursive
chown user:group file.txt         # Change ownership
chown -R user:group directory     # Recursive ownership

bash

# User Management
sudo command                      # Run as superuser
sudo su                           # Switch to root
useradd username                  # Create user
usermod -aG group user            # Add to group
passwd username                   # Change password
id                                # User and group info
whoami                            # Current user
groups                            # User groups

Linux - Process & System Management

Managing processes and system resources

linux

bash

# Process Management
ps aux                            # List all processes
ps aux | grep nginx               # Find specific process
top                               # Real-time process view
htop                              # Enhanced process viewer
kill PID                          # Kill process
kill -9 PID                       # Force kill
killall processname               # Kill by name
bg                                # Background process
fg                                # Foreground process

# System Information
df -h                             # Disk usage
du -sh directory                  # Directory size
free -h                           # Memory usage
uptime                            # System uptime
uname -a                          # System information
lscpu                             # CPU information

Linux - Networking & Text Processing

Network commands and text manipulation

linux

bash

# Networking
ping google.com                   # Test connectivity
curl https://api.example.com      # HTTP request
wget https://file.com/file.zip    # Download file
netstat -tulpn                    # Network connections
ss -tulpn                         # Socket statistics
ifconfig                          # Network interfaces
ip addr show                      # IP addresses

# Text Processing
grep "pattern" file.txt           # Search in file
grep -r "pattern" directory       # Recursive search
find /path -name "*.txt"          # Find files
sed 's/old/new/g' file.txt        # Replace text
awk '{print $1}' file.txt         # Print first column
sort file.txt                     # Sort lines
uniq file.txt                     # Remove duplicates
wc -l file.txt                    # Count lines

CI/CD - Jenkins Pipeline

Jenkins pipeline syntax and configuration

cicd

Pipeline: Automated build, test, and deploy workflow

Declarative: Simplified, opinionated syntax

Scripted: Groovy-based, more flexible

groovy

// Declarative Pipeline (Jenkinsfile)
pipeline {
    agent any
    
    environment {
        DOCKER_REGISTRY = 'registry.example.com'
    }
    
    stages {
        stage('Build') {
            steps {
                sh 'npm install'
                sh 'npm run build'
            }
        }
        
        stage('Test') {
            steps {
                sh 'npm test'
            }
        }
        
        stage('Docker Build') {
            steps {
                sh 'docker build -t myapp:${BUILD_NUMBER} .'
            }
        }
        
        stage('Deploy') {
            steps {
                sh 'kubectl apply -f k8s/'
            }
        }
    }
    
    post {
        success {
            echo 'Pipeline succeeded!'
        }
        failure {
            echo 'Pipeline failed!'
        }
    }
}

CI/CD - GitHub Actions

GitHub Actions workflow automation

cicd

yaml

# .github/workflows/ci-cd.yml
name: CI/CD Pipeline

on:
  push:
    branches: [ main, develop ]
  pull_request:
    branches: [ main ]

env:
  NODE_VERSION: '16'

jobs:
  build:
    runs-on: ubuntu-latest
    
    steps:
    - uses: actions/checkout@v3
    
    - name: Setup Node.js
      uses: actions/setup-node@v3
      with:
        node-version: ${{ env.NODE_VERSION }}
    
    - name: Install dependencies
      run: npm ci
    
    - name: Run tests
      run: npm test
    
    - name: Build application
      run: npm run build
    
    - name: Build Docker image
      run: docker build -t myapp:${{ github.sha }} .
    
    - name: Push to registry
      run: |
        docker login -u ${{ secrets.DOCKER_USER }} -p ${{ secrets.DOCKER_PASSWORD }}
        docker push myapp:${{ github.sha }}

Terraform - Infrastructure as Code

Terraform basics for infrastructure provisioning

iac

Terraform: Infrastructure as Code tool for building, changing, and versioning infrastructure

HCL: HashiCorp Configuration Language for defining resources

bash

# Terraform Commands
terraform init                    # Initialize working directory
terraform plan                    # Preview changes
terraform apply                   # Apply changes
terraform apply -auto-approve     # Skip confirmation
terraform destroy                 # Destroy infrastructure
terraform fmt                     # Format configuration
terraform validate                # Validate syntax
terraform state list              # List resources
terraform output                  # Show outputs

hcl

# Sample Terraform Configuration (main.tf)
terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 4.0"
    }
  }
}

provider "aws" {
  region = "us-east-1"
}

resource "aws_instance" "web" {
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"
  
  tags = {
    Name = "WebServer"
    Environment = "Production"
  }
}

output "instance_ip" {
  value = aws_instance.web.public_ip
}

Ansible - Configuration Management

Ansible playbooks for automation

iac

Ansible: Agentless automation tool for configuration management

Playbook: YAML file defining automation tasks

Inventory: List of managed hosts

bash

# Ansible Commands
ansible all -m ping               # Test connectivity
ansible all -m shell -a "uptime"  # Run command
ansible-playbook playbook.yml     # Run playbook
ansible-playbook playbook.yml --check  # Dry run
ansible-playbook playbook.yml -v  # Verbose
ansible-inventory --list          # List inventory

yaml

# Sample Ansible Playbook
---
- name: Deploy Web Application
  hosts: webservers
  become: yes
  
  vars:
    app_port: 3000
  
  tasks:
    - name: Install Node.js
      apt:
        name: nodejs
        state: present
        update_cache: yes
    
    - name: Copy application files
      copy:
        src: ./app/
        dest: /opt/app/
    
    - name: Install dependencies
      npm:
        path: /opt/app
    
    - name: Start application
      systemd:
        name: myapp
        state: started
        enabled: yes

AWS - Core Services

AWS CLI commands for common services

cloud

bash

# AWS CLI Configuration
aws configure                     # Setup credentials
aws configure list                # View configuration

# EC2 Operations
aws ec2 describe-instances        # List instances
aws ec2 start-instances --instance-ids i-1234567890
aws ec2 stop-instances --instance-ids i-1234567890
aws ec2 terminate-instances --instance-ids i-1234567890

# S3 Operations
aws s3 ls                         # List buckets
aws s3 ls s3://bucket-name        # List objects
aws s3 cp file.txt s3://bucket/   # Upload file
aws s3 cp s3://bucket/file.txt .  # Download file
aws s3 sync ./dir s3://bucket/    # Sync directory

# IAM Operations
aws iam list-users                # List users
aws iam list-roles                # List roles
aws iam create-user --user-name newuser

Monitoring - Prometheus & Grafana

Monitoring and alerting setup

monitoring

Prometheus: Time-series database for metrics collection

Grafana: Visualization and analytics platform

PromQL: Query language for Prometheus

yaml

# Sample Prometheus Configuration (prometheus.yml)
global:
  scrape_interval: 15s
  evaluation_interval: 15s

scrape_configs:
  - job_name: 'prometheus'
    static_configs:
      - targets: ['localhost:9090']
  
  - job_name: 'node-exporter'
    static_configs:
      - targets: ['localhost:9100']
  
  - job_name: 'kubernetes-pods'
    kubernetes_sd_configs:
      - role: pod

promql

# Common PromQL Queries
# CPU Usage
rate(node_cpu_seconds_total[5m])

# Memory Usage
node_memory_MemAvailable_bytes / node_memory_MemTotal_bytes

# HTTP Request Rate
rate(http_requests_total[5m])

# HTTP Error Rate
rate(http_requests_total{status=~"5.."}[5m])

Security - Best Practices

Security scanning and hardening

security

Security Scanning: Identify vulnerabilities in code and containers

Secrets Management: Never commit secrets to Git

Least Privilege: Minimum necessary permissions

bash

# Docker Security Scanning
docker scan image:tag             # Scan for vulnerabilities
trivy image nginx:latest          # Trivy scanner

# Container Security
docker run --read-only nginx      # Read-only filesystem
docker run --cap-drop ALL nginx   # Drop capabilities
docker run --security-opt no-new-privileges nginx

yaml

# Kubernetes Security
# Security Context
securityContext:
  runAsNonRoot: true
  runAsUser: 1000
  readOnlyRootFilesystem: true
  capabilities:
    drop:
      - ALL

# Network Policies
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: deny-all
spec:
  podSelector: {}
  policyTypes:
  - Ingress
  - Egress

Complete DevOps Cheatsheet

Contents

Docker - Container Basics

Docker - Images

Docker - Networks & Volumes

Docker Compose

Kubernetes - Cluster Basics

Kubernetes - Pods & Deployments

Kubernetes - Services & ConfigMaps

Kubernetes - YAML Manifests

Git - Basic Operations

Git - Branching & Merging

Git - Advanced Operations

Linux - File Operations

Linux - Permissions & Users

Linux - Process & System Management

Linux - Networking & Text Processing

CI/CD - Jenkins Pipeline

CI/CD - GitHub Actions

Terraform - Infrastructure as Code

Ansible - Configuration Management

AWS - Core Services

Monitoring - Prometheus & Grafana

Security - Best Practices