1. Basic Commands for Checking Disk Spaceunsetunset

1.1 Check Disk Usage

# Check disk usage for all mounted points
df -h


# Check disk usage for a specific directory
df -h /home

1.2 Find Large Files and Directories

# Find files larger than 100MB in the current directory
find . -type f -size +100M -exec ls -lh {} \;


# Find files larger than 1GB in the root directory
find / -type f -size +1G -exec ls -lh {} \;

unsetunset2. Advanced Methods for Finding Large Filesunsetunset

2.1 Using the du Command

# Show the largest 10 directories in the current directory
du -sh * | sort -rh | head -10


# Show the largest 10 directories in the root directory
du -sh /* | sort -rh | head -10


# Show large files in a specific directory
du -ah /var/log | sort -rh | head -20

2.2 Comprehensive Search Script

#!/bin/bash
# Find the largest files and directories in the system
echo "=== Largest 10 Directories ==="
du -h / 2>/dev/null | sort -hr | head -10

echo -e "\n=== Largest 10 Files ==="
find / -type f -size +100M 2>/dev/null | xargs ls -lh | sort -k5 -hr | head -10

unsetunset3. Common Large File Types Analysisunsetunset

3.1 Log File Cleanup

# Check the size of the log directory
du -sh /var/log/*


# Clean old log files (keep the last 7 days)
find /var/log -name "*.log" -mtime +7 -delete


# Compress old log files
find /var/log -name "*.log" -mtime +3 -exec gzip {} \;

3.2 Cache File Cleanup

# Check the size of the cache directory
du -sh /tmp /var/tmp /var/cache/*


# Clean temporary files
rm -rf /tmp/*
rm -rf /var/tmp/*


# Clean package manager cache
yum clean all    # CentOS/RHEL
apt-get clean    # Ubuntu/Debian

unsetunset4. Practical Cleanup Scriptsunsetunset

4.1 Automated Cleanup Script

#!/bin/bash
# disk_cleanup.sh - Automated cleanup script for large files


LOG_FILE="/var/log/disk_cleanup.log"


# Log message function
log_message() {
    echo "$(date '+%Y-%m-%d %H:%M:%S') - $1" >> $LOG_FILE
}


# Check disk usage
check_disk_usage() {
    local usage=$(df / | awk 'NR==2 {print $5}' | sed 's/%//')
    if [ $usage -gt 80 ]; then
        log_message "Warning: Disk usage too high: ${usage}%"
        return 1
    fi
    return 0
}


# Cleanup log files
cleanup_logs() {
    log_message "Starting log file cleanup..."
    
    # Delete logs older than 30 days
    find /var/log -name "*.log" -mtime +30 -delete
    
    # Compress old logs
    find /var/log -name "*.log" -mtime +7 -exec gzip {} \;
    
    log_message "Log cleanup completed"
}


# Cleanup temporary files
cleanup_temp() {
    log_message "Starting temporary file cleanup..."
    
    # Clean expired temporary files
    find /tmp -type f -mtime +1 -delete
    find /var/tmp -type f -mtime +1 -delete
    
    log_message "Temporary file cleanup completed"
}


# Main execution flow
main() {
    log_message "=== Starting disk cleanup task ==="
    
    if check_disk_usage; then
        cleanup_logs
        cleanup_temp
        log_message "=== Disk cleanup task completed ==="
    else
        log_message "Disk usage too high, skipping cleanup operation"
    fi
}


main

4.2 Scheduled Cleanup Tasks

# Add to crontab for periodic execution
# Execute cleanup every Sunday at 2 AM
0 2 * * 0 /path/to/disk_cleanup.sh


# Check disk usage every day at 3 AM
0 3 * * * df -h | grep -E "(Filesystem|/)" > /tmp/disk_usage.txt

unsetunset5. Safety Cleanup Precautionsunsetunset

5.1 Check Before Cleanup

# Check file details to avoid accidentally deleting important files
ls -la /var/log/
ls -la /tmp/


# Check file permissions and owners
ls -l /var/log/messages

5.2 Verify Cleanup Operations

# Use dry-run mode to preview files to be deleted
find /var/log -name "*.log" -mtime +7 -print


# Backup before deletion
cp /var/log/syslog /var/log/syslog.backup
rm /var/log/syslog

unsetunset6. Monitoring and Alertsunsetunset

6.1 Disk Monitoring Script

#!/bin/bash
# disk_monitor.sh - Disk monitoring script


THRESHOLD=80
EMAIL="[email protected]"


# Check disk usage
check_disks() {
    df -h | grep -vE '^Filesystem|tmpfs|cdrom' | while read line; do
        usage=$(echo $line | awk '{print $5}' | sed 's/%//')
        partition=$(echo $line | awk '{print $1}')
        mount_point=$(echo $line | awk '{print $6}')
        
        if [ $usage -gt $THRESHOLD ]; then
            echo "Warning: $mount_point disk usage $usage%"
            # Send email notification
            echo "Disk usage too high, please address it" | mail -s "Disk Warning" $EMAIL
        fi
    done
}


check_disks

6.2 Create Monitoring Service

# Create systemd service for periodic monitoring
cat > /etc/systemd/system/disk-monitor.service << EOF
[Unit]
Description=Disk Usage Monitor
After=network.target


[Service]
Type=oneshot
ExecStart=/usr/local/bin/disk_monitor.sh
User=root


[Install]
WantedBy=multi-user.target
EOF


# Enable service
systemctl enable disk-monitor.service

unsetunset7. Common Problem Solutionsunsetunset

7.1 Deleted but Still in Use Files

# Find deleted files still held by processes
lsof +L1


# Restart related services to release files
systemctl restart nginx
systemctl restart httpd

7.2 Large File Recovery

# If important files are accidentally deleted, try the following methods:
# 1. Use testdisk or photorec for recovery
# 2. Check for backups
# 3. Check filesystem logs
journalctl -f

unsetunset8. Best Practice Recommendationsunsetunset

1. Regular Monitoring: Set up periodic checks for disk usage
2. Backup Important Data: Ensure important data is backed up before cleanup
3. Step-by-Step Cleanup: Test on a small scale before large-scale execution
4. Document Operations: Keep detailed records of the cleanup process and results
5. Set Thresholds: Establish a reasonable alert mechanism for disk usage

By following the above methods, you can effectively manage and maintain disk space on Linux servers, ensuring stable system operation.