10 Essential Linux Scripts Every System Administrator Should Know

As a system administrator, managing Linux servers can be time-consuming and tedious. To make your life easier, we’ve compiled a list of 10 essential Linux scripts that will help you automate tasks, streamline processes, and improve overall efficiency. These scripts cover a wide range of functions, from monitoring system performance to managing user accounts. Let’s dive in!

1. System Load and Resource Usage Monitoring

Keep track of your server’s system load and resource usage with this simple shell script:

#!/bin/bash
echo "System Load: $(uptime)"
echo "Free Memory: $(free -h | grep Mem | awk '{print $4}')"
echo "Free Disk Space: $(df -h / | grep / | awk '{print $4}')"

2. Automated Backup with Timestamp

Create backups of your critical files and directories with this script, which appends a timestamp to the backup file:

#!/bin/bash
SOURCE="/path/to/your/important/files"
DESTINATION="/path/to/your/backup/directory"
TIMESTAMP=$(date +"%Y%m%d_%H%M%S")
tar czf "${DESTINATION}/backup_${TIMESTAMP}.tar.gz" "${SOURCE}"

3. User Account Management

Efficiently manage user accounts by automating the process of creating, deleting, and updating users with this script:

#!/bin/bash
# Usage: ./user_management.sh [create|delete|update] username

ACTION=$1
USERNAME=$2

case "${ACTION}" in
  create)
    sudo useradd "${USERNAME}"
    ;;
  delete)
    sudo userdel -r "${USERNAME}"
    ;;
  update)
    sudo passwd "${USERNAME}"
    ;;
  *)
    echo "Invalid action. Usage: ./user_management.sh [create|delete|update] username"
    ;;
esac

4. Log File Rotation

Prevent log files from growing too large by automating log file rotation with this script:

#!/bin/bash
LOG_FILE="/path/to/your/logfile.log"
MAX_SIZE=10485760 # 10 MB
CURRENT_SIZE=$(wc -c <"${LOG_FILE}")

if [ "${CURRENT_SIZE}" -gt "${MAX_SIZE}" ]; then
    TIMESTAMP=$(date +"%Y%m%d_%H%M%S")
    mv "${LOG_FILE}" "${LOG_FILE}_${TIMESTAMP}"
    touch "${LOG_FILE}"
fi

5. Disk Usage Notification

Receive notifications when disk usage exceeds a certain threshold with this disk usage notification script:

#!/bin/bash
THRESHOLD=90
EMAIL="your-email@example.com"
PARTITION="/"

USAGE=$(df -h "${PARTITION}" | awk 'NR==2 {print $5}' | sed 's/%//')

if [ "${USAGE}" -gt "${THRESHOLD}" ]; then
    echo "Disk usage on ${PARTITION} is at ${USAGE}%. Consider freeing up some space." | mail -s "Disk Usage Alert" "${EMAIL}"
fi

6. Monitor and Restart Services

Automatically monitor and restart essential services if they go down with this script:

“`html

#!/bin/bash
SERVICE="your-service-name"
EMAIL="your-email@example.com"

if systemctl is-active --quiet "${SERVICE}"; then
    echo "${SERVICE} is running."
else
    echo "${SERVICE} is not running. Restarting..." | mail -s "${SERVICE} Restart Alert" "${EMAIL}"
    systemctl start "${SERVICE}"
fi

7. IP Address Information

Retrieve your server’s public and private IP address information with this script:

“`html

#!/bin/bash
PUBLIC_IP=$(curl -s https://ipinfo.io/ip)
PRIVATE_IP=$(hostname -I | awk '{print $1}')

echo "Public IP: ${PUBLIC_IP}"
echo "Private IP: ${PRIVATE_IP}"

8. Monitor SSL Certificate Expiration

Monitor your SSL certificate expiration dates and receive notifications with this script:

“`html

#!/bin/bash
DOMAIN="yourdomain.com"
EMAIL="your-email@example.com"
DAYS_THRESHOLD=30

EXPIRATION_DATE=$(echo | openssl s_client -servername "${DOMAIN}" -connect "${DOMAIN}:443" 2>/dev/null | openssl x509 -enddate -noout | awk -F= '{print $2}')
EXPIRATION_SECONDS=$(date -d "${EXPIRATION_DATE}" +%s)
CURRENT_SECONDS=$(date +%s)
SECONDS_DIFFERENCE=$((EXPIRATION_SECONDS - CURRENT_SECONDS))
DAYS_DIFFERENCE=$((SECONDS_DIFFERENCE / 86400))

if [ "${DAYS_DIFFERENCE}" -lt "${DAYS_THRESHOLD}" ]; then
    echo "The SSL certificate for ${DOMAIN} will expire in ${DAYS_DIFFERENCE} days (${EXPIRATION_DATE})." | mail -s "SSL Certificate Expiration Alert" "${EMAIL}"
fi

9. Update System Packages

Automate system package updates with this script:

“`html

#!/bin/bash
sudo apt-get update
sudo apt-get upgrade -y
sudo apt-get autoremove -y

10. Check for Failed SSH Login Attempts

Monitor failed SSH login attempts and receive notifications with this script:

“`html

#!/bin/bash
LOG_FILE="/var/log/auth.log"
EMAIL="your-email@example.com"
FAILED_ATTEMPTS=$(grep "Failed password" "${LOG_FILE}" | wc -l)

if [ "${FAILED_ATTEMPTS}" -gt 0 ]; then
    echo "There have been ${FAILED_ATTEMPTS} failed SSH login attempts." | mail -s "SSH Login Alert" "${EMAIL}"
fi

Conclusion

These 10 essential Linux scripts can significantly simplify a system administrator’s tasks and improve overall productivity. By incorporating these scripts into your daily workflow, you’ll be better equipped to manage and maintain Linux servers with ease. Start using these Linux scripts today to save time, reduce manual effort, and enhance your system administration skills.