linux-production-shell-scripts

# Linux Production Shell Scripts ## Purpose Provide production-ready shell script templates for common Linux system administration tasks including backups, monitoring, user management, log analysis, and automation. These scripts serve as building blocks for security operations and penetration testing environments. ## Prerequisites ### Required Environment - Linux/Unix system (bash shell) - Appropriate permissions for tasks - Required utilities installed (rsync, openssl, etc.) ### Required Knowledge - Basic bash scripting - Linux file system structure - System administration concepts ## Outputs and Deliverables 1. **Backup Solutions** - Automated file and database backups 2. **Monitoring Scripts** - Resource usage tracking 3. **Automation Tools** - Scheduled task execution 4. **Security Scripts** - Password management, encryption ## Core Workflow ### Phase 1: File Backup Scripts **Basic Directory Backup** ```bash #!/bin/bash backup_dir="/path/to/backup" source_dir="/path/to/source" # Create a timestamped backup of the source directory tar -czf "$backup_dir/backup_$(date +%Y%m%d_%H%M%S).tar.gz" "$source_dir" echo "Backup completed: backup_$(date +%Y%m%d_%H%M%S).tar.gz" ``` **Remote Server Backup** ```bash #!/bin/bash source_dir="/path/to/source" remote_server="user@remoteserver:/path/to/backup" # Backup files/directories to a remote server using rsync rsync -avz --progress "$source_dir" "$remote_server" echo "Files backed up to remote server." ``` **Backup Rotation Script** ```bash #!/bin/bash backup_dir="/path/to/backups" max_backups=5 # Rotate backups by deleting the oldest if more than max_backups while [ $(ls -1 "$backup_dir" | wc -l) -gt "$max_backups" ]; do oldest_backup=$(ls -1t "$backup_dir" | tail -n 1) rm -r "$backup_dir/$oldest_backup" echo "Removed old backup: $oldest_backup" done echo "Backup rotation completed." ``` **Database Backup Script** ```bash #!/bin/bash database_name="your_database" db_user="username" db_pass="password" output_file="database_backup_$(date +%Y%m%d).sql" # Perform database backup using mysqldump mysqldump -u "$db_user" -p"$db_pass" "$database_name" > "$output_file" gzip "$output_file" echo "Database backup created: $output_file.gz" ``` ### Phase 2: System Monitoring Scripts **CPU Usage Monitor** ```bash #!/bin/bash threshold=90 # Monitor CPU usage and trigger alert if threshold exceeded cpu_usage=$(top -bn1 | grep "Cpu(s)" | awk '{print $2}' | cut -d. -f1) if [ "$cpu_usage" -gt "$threshold" ]; then echo "ALERT: High CPU usage detected: $cpu_usage%" # Add notification logic (email, slack, etc.) # mail -s "CPU Alert" admin@example.com <<< "CPU usage: $cpu_usage%" fi ``` **Disk Space Monitor** ```bash #!/bin/bash threshold=90 partition="/dev/sda1" # Monitor disk usage and trigger alert if threshold exceeded disk_usage=$(df -h | grep "$partition" | awk '{print $5}' | cut -d% -f1) if [ "$disk_usage" -gt "$threshold" ]; then echo "ALERT: High disk usage detected: $disk_usage%" # Add alert/notification logic here fi ``` **CPU Usage Logger** ```bash #!/bin/bash output_file="cpu_usage_log.txt" # Log current CPU usage to a file with timestamp timestamp=$(date '+%Y-%m-%d %H:%M:%S') cpu_usage=$(top -bn1 | grep 'Cpu(s)' | awk '{print $2}' | cut -d. -f1) echo "$timestamp - CPU Usage: $cpu_usage%" >> "$output_file" echo "CPU usage logged." ``` **System Health Check** ```bash #!/bin/bash output_file="system_health_check.txt" # Perform system health check and save results to a file { echo "System Health Check - $(date)" echo "================================" echo "" echo "Uptime:" uptime echo "" echo "Load Average:" cat /proc/loadavg echo "" echo "Memory Usage:" free -h echo "" echo "Disk Usage:" df -h echo "" echo "Top Processes:" ps aux --sort=-%cpu | head -10 } > "$output_file" echo "System health check saved to $output_file" ``` ### Phase 3: User Management Scripts **User Account Creation** ```bash #!/bin/bash username="newuser" # Check if user exists; if not, create new user if id "$username" &>/dev/null; then echo "User $username already exists." else useradd -m -s /bin/bash "$username" echo "User $username created." # Set password interactively passwd "$username" fi ``` **Password Expiry Checker** ```bash #!/bin/bash output_file="password_expiry_report.txt" # Check password expiry for users with bash shell echo "Password Expiry Report - $(date)" > "$output_file" echo "=================================" >> "$output_file" IFS=$'\n' for user in $(grep "/bin/bash" /etc/passwd | cut -d: -f1); do password_expires=$(chage -l "$user" 2>/dev/null | grep "Password expires" | awk -F: '{print $2}') echo "User: $user - Password Expires: $password_expires" >> "$output_file" done unset IFS echo "Password expiry report saved to $output_file" ``` ### Phase 4: Security Scripts **Password Generator** ```bash #!/bin/bash length=${1:-16} # Generate a random password password=$(openssl rand -base64 48 | tr -dc 'a-zA-Z0-9!@#$%^&*' | head -c"$length") echo "Generated password: $password" ``` **File Encryption Script** ```bash #!/bin/bash file="$1" action="${2:-encrypt}" if [ -z "$file" ]; then echo "Usage: $0 <file> [encrypt|decrypt]" exit 1 fi if [ "$action" == "encrypt" ]; then # Encrypt file using AES-256-CBC openssl enc -aes-256-cbc -salt -pbkdf2 -in "$file" -out "$file.enc" echo "File encrypted: $file.enc" elif [ "$action" == "decrypt" ]; then # Decrypt file output_file="${file%.enc}" openssl enc -aes-256-cbc -d -pbkdf2 -in "$file" -out "$output_file" echo "File decrypted: $output_file" fi ``` ### Phase 5: Log Analysis Scripts **Error Log Extractor** ```bash #!/bin/bash logfile="${1:-/var/log/syslog}" output_file="error_log_$(date +%Y%m%d).txt" # Extract lines with "ERROR" from the log file grep -i "error\|fail\|critical" "$logfile" > "$output_file" echo "Error log created: $output_file" echo "Total errors found: $(wc -l < "$output_file")" ``` **Web Server Log Analyzer** ```bash #!/bin/bash log_file="${1:-/var/log/apache2/access.log}" echo "Web Server Log Analysis" echo "========================" echo "" echo "Top 10 IP Addresses:" awk '{print $1}' "$log_file" | sort | uniq -c | sort -rn | head -10 echo "" echo "Top 10 Requested URLs:" awk '{print $7}' "$log_file" | sort | uniq -c | sort -rn | head -10 echo "" echo "HTTP Status Code Distribution:" awk '{print $9}' "$log_file" | sort | uniq -c | sort -rn ``` ### Phase 6: Network Scripts **Network Connectivity Checker** ```bash #!/bin/bash hosts=("8.8.8.8" "1.1.1.1" "google.com") echo "Network Connectivity Check" echo "==========================" for host in "${hosts[@]}"; do if ping -c 1 -W 2 "$host" &>/dev/null; then echo "[UP] $host is reachable" else echo "[DOWN] $host is unreachable" fi done ``` **Website Uptime Checker** ```bash #!/bin/bash websites=("https://google.com" "https://github.com") log_file="uptime_log.txt" echo "Website Uptime Check - $(date)" >> "$log_file" for website in "${websites[@]}"; do if curl --output /dev/null --silent --head --fail --max-time 10 "$website"; then echo "[UP] $website is accessible" | tee -a "$log_file" else echo "[DOWN] $website is inaccessible" | tee -a "$log_file" fi done ``` **Network Interface Info** ```bash #!/bin/bash interface="${1:-eth0}" echo "Network Interface Information: $interface" echo "=========================================" ip addr show "$interface" 2>/dev/null || ifconfig "$interface" 2>/dev/null echo "" echo "Routing Table:" ip route | grep "$interface" ``` ### Phase 7: Automation Scripts **Automated Package Installation** ```bash #!/bin/bash packages=("vim" "htop" "curl" "wget" "git") echo "Installing packages..." for package in "${packages[@]}"; do if dpkg -l | grep -q "^ii $package"; then echo "[SKIP] $package is already installed" else sudo apt-get install -y "$package" echo "[INSTALLED] $package" fi done echo "Package installation completed." ``` **Task Scheduler (Cron Setup)** ```bash #!/bin/bash scheduled_task="/path/to/your_script.sh" schedule_time="0 2 * * *" # Run at 2 AM daily # Add task to crontab (crontab -l 2>/dev/null; echo "$schedule_time $scheduled_task") | crontab - echo "Task scheduled: $schedule_time $scheduled_task" ``` **Service Restart Script** ```bash #!/bin/bash service_name="${1:-apache2}" # Restart a specified service if systemctl is-active --quiet "$service_name"; then echo "Restarting $service_name..." sudo systemctl restart "$service_name" echo "Service $service_name restarted." else