Disk Space Alert Script

Monitor avialable disk space and send alerts when below threshold.

Prerequisites

Install email utilities:

yum install mailx -y

Configure email settings in /etc/mail.rc.

Implementation

Create a monitoring script at /root/disk_check.sh:

#!/bin/bash

# Check available disk space
available_space=$(df / | awk 'NR==2 {print $4}')

# Convert to gigabytes
space_gb=$((available_space / 1024 / 1024))

# Alert if less than 20GB
if [ "$space_gb" -lt 20 ]; then
    echo "Warning: Available disk space is ${space_gb}GB" | mail -s "Disk Space Alert" admin@example.com
fi

Schedule daily execution using cron:

vim /etc/crontab
0 0 * * * root /bin/bash /root/disk_check.sh

Web Server Status Checker

Verify service status through process and port inspetcion.

Process-Based Check

#!/bin/bash

# Verify nginx process
process_count=$(pgrep nginx | wc -l)

if [ "$process_count" -gt 0 ]; then
    echo "nginx is active"
else
    echo "nginx is inactive, initiating startup..."
    
    # Install and start services
    yum install nginx -y > /dev/null
    systemctl start nginx
    systemctl start firewalld
    
    # Configure firewall
    firewall-cmd --permanent --zone=public --add-service=http > /dev/null
    firewall-cmd --permanent --zone=public --add-port=80/tcp > /dev/null
    firewall-cmd --reload > /dev/null
    
    echo "nginx has been started"
fi

Port-Based Verification

#!/bin/bash

# Check for listening HTTP port
port_check=$(ss -tuln | grep :80 | wc -l)

if [ "$port_check" -gt 0 ]; then
    echo "nginx is active"
else
    echo "nginx is inactive, initiating startup..."
    
    # Install and start services
    yum install nginx -y > /dev/null
    systemctl start nginx
    systemctl start firewalld
    
    # Configure firewall
    firewall-cmd --permanent --zone=public --add-service=http > /dev/null
    firewall-cmd --permanent --zone=public --add-port=80/tcp > /dev/null
    firewall-cmd --reload > /dev/null
    
    echo "nginx has been started"
fi

Web Accessibility Validator

Test web server connectivity and return appropriate status codes.

#!/bin/bash

# Retrieve IP address
server_ip=$(ip addr show ens32 | grep inet | awk '{print $2}' | cut -d'/' -f1)

# Test connection
response=$(curl -s -o /dev/null -w "%{http_code}" http://$server_ip)

case $response in
    200)
        echo "web server is running"
        ;;
    *)
        echo "web not accessible"
        exit 12
        ;;
esac