🛠️ Linux Shell Scripting – Automate Admin Tasks Like a Pro

Introduction

Linux Shell Scripting: System administrators spend a lot of time performing repetitive tasks like backups, user management, and system monitoring. Shell scripting can automate these tasks, saving time and reducing errors.

In this guide, we’ll cover:
✅ Writing shell scripts for automation
✅ Automating backups and user management
✅ Monitoring system performance with scripts
✅ Scheduling scripts with cron jobs

By the end, you’ll be able to write efficient shell scripts for system administration.

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📌 1. Automating Backups with Shell Scripts

Backing up files and directories is essential for system recovery.

Example: Simple Backup Script

#!/bin/bash

backup_dir="/backup"
source_dir="/home/user"
timestamp=$(date +%Y-%m-%d_%H-%M-%S)
backup_file="$backup_dir/home_backup_$timestamp.tar.gz"

echo "Starting backup..."
tar -czf $backup_file $source_dir
echo "Backup completed: $backup_file"

Steps to Automate This Script:

1️⃣ Save this script as backup.sh.
2️⃣ Make it executable:

chmod +x backup.sh

3️⃣ Run it manually:

./backup.sh

4️⃣ Schedule it with cron to run daily at 2 AM:

crontab -e

Add this line:

0 2 * * * /path/to/backup.sh

✅ Now, your home directory will be backed up automatically every night!

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📌 2. Automating User Management Tasks

Creating users manually can be time-consuming. Let’s automate it!

Example: Create Multiple Users from a File

#!/bin/bash

user_list="users.txt"

while IFS= read -r user
do
    sudo useradd -m "$user"
    echo "User $user created successfully!"
done < "$user_list"

Steps to Use This Script:

1️⃣ Create a file users.txt and add usernames, one per line.
2️⃣ Save the script as create_users.sh.
3️⃣ Make it executable:

chmod +x create_users.sh

4️⃣ Run the script:

./create_users.sh

✅ Now, all users in users.txt will be created automatically!

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📌 3. Automating System Monitoring

Monitor CPU, memory, and disk usage with a shell script.

Example: System Health Monitoring Script

#!/bin/bash

echo "System Health Report - $(date)"
echo "----------------------------------"
echo "Uptime:"
uptime
echo ""

echo "CPU Usage:"
top -b -n1 | grep "Cpu(s)"
echo ""

echo "Memory Usage:"
free -h
echo ""

echo "Disk Usage:"
df -h

Steps to Use This Script:

1️⃣ Save it as system_monitor.sh.
2️⃣ Make it executable:

chmod +x system_monitor.sh

3️⃣ Run it manually:

./system_monitor.sh

4️⃣ Automate it to run every hour using cron:

crontab -e

Add this line:

0 * * * * /path/to/system_monitor.sh >> /var/log/system_health.log

✅ Now, the system will be monitored every hour, and logs will be saved!

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📌 4. Automating Log Cleanup

Log files can grow large and consume disk space. Let’s automate log cleanup.

Example: Delete Old Log Files

#!/bin/bash

log_dir="/var/log"
days=30

find $log_dir -type f -name "*.log" -mtime +$days -exec rm -f {} \;
echo "Old log files deleted!"

Steps to Use This Script:

1️⃣ Save it as log_cleanup.sh.
2️⃣ Make it executable:

chmod +x log_cleanup.sh

3️⃣ Run it manually:

./log_cleanup.sh

4️⃣ Automate it to run weekly:

crontab -e

Add this line:

0 0 * * 0 /path/to/log_cleanup.sh

✅ Now, old log files will be deleted every Sunday at midnight!

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📌 5. Sending System Alerts via Email

If system load gets too high, send an email alert.

Example: Email Alert for High CPU Usage

#!/bin/bash

threshold=80
cpu_load=$(top -b -n1 | grep "Cpu(s)" | awk '{print $2 + $4}')

if (( $(echo "$cpu_load > $threshold" | bc -l) )); then
    echo "High CPU Usage Alert! Current Load: $cpu_load%" | mail -s "CPU Alert" admin@example.com
fi

Steps to Use This Script:

1️⃣ Install mail utilities:

sudo apt install mailutils

2️⃣ Save it as cpu_alert.sh.
3️⃣ Make it executable:

chmod +x cpu_alert.sh

4️⃣ Automate it to check every 5 minutes:

crontab -e

Add this line:

*/5 * * * * /path/to/cpu_alert.sh

✅ Now, you’ll receive an email alert if CPU usage goes beyond 80%!

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🎯 Final Thoughts

With shell scripting, you can automate backups, user management, system monitoring, and more, making your job as an administrator much easier.

Learn More:

Common Challenges in Incident Management

Essential Technical Skills for Aspiring Incident Managers

Understanding the ITIL Framework for Incident Management

Key Roles and Responsibilities in Incident Management

What is Incident Management?

What is Linux?

Linux vs Windows vs macOS 

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📌 Call to Action (CTA)

💬 Which admin task do you want to automate next? Let us know in the comments!
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