Automation Scripts

Automation is the heart of DevOps. Learn to create scripts that automate routine tasks, deployments, and system maintenance.

System Maintenance Script

Automate common maintenance tasks:

#!/bin/bash
set -euo pipefail

echo "=== System Maintenance ==="

# Update package lists
echo "Updating packages..."
apt-get update -qq

# Clean old packages
echo "Cleaning up..."
apt-get autoremove -y -qq
apt-get autoclean -qq

# Clear temp files
echo "Clearing temp files..."
find /tmp -type f -mtime +7 -delete 2>/dev/null || true

# Check disk usage
echo "Disk usage:"
df -h | grep -E '^/dev'

echo "Maintenance complete!"

File Organizer

Automatically organize files:

#!/bin/bash

SOURCE_DIR="${1:-.}"
TARGET_DIR="${2:-./organized}"

mkdir -p "$TARGET_DIR"/{images,documents,videos,audio,other}

for file in "$SOURCE_DIR"/*; do
    [ -f "$file" ] || continue

    case "${file,,}" in
        *.jpg|*.jpeg|*.png|*.gif)
            mv "$file" "$TARGET_DIR/images/" ;;
        *.pdf|*.doc|*.docx|*.txt)
            mv "$file" "$TARGET_DIR/documents/" ;;
        *.mp4|*.avi|*.mkv)
            mv "$file" "$TARGET_DIR/videos/" ;;
        *.mp3|*.wav|*.flac)
            mv "$file" "$TARGET_DIR/audio/" ;;
        *)
            mv "$file" "$TARGET_DIR/other/" ;;
    esac
done

echo "Files organized!"

Exercise: File Cleanup

Automate cleanup:

Deployment Script

Basic application deployment:

#!/bin/bash
set -euo pipefail

APP_NAME="myapp"
DEPLOY_DIR="/var/www/$APP_NAME"
REPO_URL="git@github.com:user/$APP_NAME.git"
BRANCH="${1:-main}"

log() { echo "[$(date '+%H:%M:%S')] $*"; }

log "Starting deployment of $APP_NAME ($BRANCH)"

# Backup current version
if [ -d "$DEPLOY_DIR" ]; then
    log "Backing up current version..."
    tar -czf "/backup/${APP_NAME}_$(date +%Y%m%d_%H%M%S).tar.gz" "$DEPLOY_DIR"
fi

# Clone or pull
if [ -d "$DEPLOY_DIR/.git" ]; then
    log "Pulling latest changes..."
    cd "$DEPLOY_DIR"
    git fetch origin
    git checkout "$BRANCH"
    git pull origin "$BRANCH"
else
    log "Cloning repository..."
    git clone -b "$BRANCH" "$REPO_URL" "$DEPLOY_DIR"
    cd "$DEPLOY_DIR"
fi

# Install dependencies
log "Installing dependencies..."
npm install --production

# Restart service
log "Restarting service..."
systemctl restart "$APP_NAME"

log "Deployment complete!"

Scheduled Tasks

Create scripts for cron:

#!/bin/bash
# /etc/cron.daily/cleanup.sh

LOG="/var/log/cleanup.log"

{
    echo "=== Cleanup started: $(date) ==="

    # Remove old logs
    find /var/log -name "*.log" -mtime +30 -delete

    # Clear cache
    rm -rf /var/cache/app/*

    # Remove old sessions
    find /var/lib/php/sessions -mtime +1 -delete

    echo "=== Cleanup finished: $(date) ==="
} >> "$LOG" 2>&1

Health Check Script

Monitor system health:

#!/bin/bash

check_disk() {
    usage=$(df / | awk 'NR==2 {print $5}' | tr -d '%')
    if [ "$usage" -gt 90 ]; then
        echo "CRITICAL: Disk usage at ${usage}%"
        return 1
    fi
    echo "OK: Disk usage at ${usage}%"
}

check_memory() {
    free_mem=$(free | awk '/Mem:/ {printf "%.0f", $4/$2 * 100}')
    if [ "$free_mem" -lt 10 ]; then
        echo "CRITICAL: Only ${free_mem}% memory free"
        return 1
    fi
    echo "OK: ${free_mem}% memory free"
}

check_service() {
    local service="$1"
    if systemctl is-active --quiet "$service"; then
        echo "OK: $service is running"
    else
        echo "CRITICAL: $service is not running"
        return 1
    fi
}

# Run checks
STATUS=0
check_disk || STATUS=1
check_memory || STATUS=1
check_service nginx || STATUS=1

exit $STATUS

Exercise: Service Check

Check if a process is running:

Batch Processing

Process multiple items:

#!/bin/bash

# Process images in parallel
process_images() {
    local src_dir="$1"
    local dest_dir="$2"

    mkdir -p "$dest_dir"

    find "$src_dir" -name "*.jpg" | while read -r img; do
        name=$(basename "$img")
        echo "Processing: $name"
        # Example: resize image
        convert "$img" -resize 800x600 "$dest_dir/$name" &
    done

    wait    # Wait for all background jobs
    echo "All images processed"
}

process_images ./uploads ./thumbnails

CI/CD Helper Script

#!/bin/bash
set -euo pipefail

STAGE="${1:-test}"

run_tests() {
    echo "Running tests..."
    npm test
}

run_lint() {
    echo "Running linter..."
    npm run lint
}

build_app() {
    echo "Building application..."
    npm run build
}

deploy() {
    local env="$1"
    echo "Deploying to $env..."
    # Deploy logic here
}

case "$STAGE" in
    test)
        run_tests
        ;;
    lint)
        run_lint
        ;;
    build)
        run_lint
        run_tests
        build_app
        ;;
    deploy-staging)
        build_app
        deploy staging
        ;;
    deploy-prod)
        build_app
        deploy production
        ;;
    *)
        echo "Usage: $0 {test|lint|build|deploy-staging|deploy-prod}"
        exit 1
        ;;
esac

Automation Best Practices

1. Idempotent scripts - Safe to run multiple times
2. Logging - Record what happened and when
3. Error handling - Fail gracefully, notify on errors
4. Dry-run mode - Preview changes before applying
5. Configuration - Use variables for customization
6. Testing - Test scripts before production use

#!/bin/bash
# Best practices example

DRY_RUN="${DRY_RUN:-false}"

run() {
    echo "Would run: $*"
    [ "$DRY_RUN" = "true" ] && return
    "$@"
}

# Usage
run rm -rf /tmp/old_files
# DRY_RUN=true ./script.sh  # Preview mode

Key Takeaways

• Automate repetitive tasks to save time
• Use set -euo pipefail for safety
• Add logging for troubleshooting
• Implement health checks for monitoring
• Use cron for scheduled automation
• Create idempotent scripts when possible
• Add dry-run modes for destructive operations
• Document your automation scripts