Monitoring Disk Space and Preventing Full Disk Issues

Check Disk Usage

# Overview of all filesystems
df -h

# Check inode usage (running out of inodes is as bad as disk space)
df -i

# Size of current directory
du -sh .

# Top 10 largest directories
du -h --max-depth=1 / | sort -rh | head -10

Find Large Files

# Files over 100 MB
find / -type f -size +100M -exec ls -lh {} \; 2>/dev/null

# Largest files in /var
find /var -type f -exec du -h {} + 2>/dev/null | sort -rh | head -20

Common Space Consumers

Automated Monitoring

Create /usr/local/bin/disk-alert.sh:

#!/bin/bash
THRESHOLD=85
USAGE=$(df / | tail -1 | awk '{print $5}' | tr -d '%')
if [ "$USAGE" -gt "$THRESHOLD" ]; then
    echo "WARNING: Disk usage is ${USAGE}% on $(hostname)" | mail -s "Disk Alert" admin@example.com
fi

chmod +x /usr/local/bin/disk-alert.sh
# Run hourly
echo "0 * * * * root /usr/local/bin/disk-alert.sh" >> /etc/crontab

Preventive Measures

• Set up logrotate for all application logs
• Schedule regular cleanup of temporary files
• Use ncdu for interactive disk usage analysis
• Monitor with alerting tools (Netdata, Prometheus)