du command

Working with du command in linux efficiently

1. Find the Largest Directories (Sorted)

sudo du -ahx / | sort -rh | head -20

• -a → Show both files and directories
• -h → Human-readable sizes (e.g., MB, GB)
• -x → Stay on the same filesystem (avoid mounted drives)
• sort -rh → Sort by size, largest first
• head -20 → Show top 20 largest directories/files

2. Find the Largest Directories Only (Excluding Files)

sudo du -hx --max-depth=3 / | sort -rh | head -20

• --max-depth=3 → Limits output to top 3 levels for better readability

3. Find the Largest Files (Over 500MB)

sudo find / -type f -size +500M -exec du -h {} + | sort -rh | head -20

• -type f → Only files
• -size +500M → Files larger than 500MB
• du -h → Show file sizes in human-readable format

4. Exclude Certain Directories (Like /proc, /sys, etc.)

sudo du -ahx --exclude={/proc,/sys,/dev,/run,/snap,/tmp,/mnt,/media} / | sort -rh | head -20

• This avoids system directories that don’t consume real disk space.

5. Find the Largest Users (Disk Usage by User)

sudo du -sh /home/* 2>/dev/null

• This shows how much each user is consuming in /home.

6. Save Output to a File

If you want to analyze later:

sudo du -ahx / | sort -rh > large_files.txt

Then open it:

less large_files.txt

Next Steps After Finding Large Files:

1. Check logs:

   sudo du -sh /var/log/*
   

   • You can clear logs with:

     sudo journalctl --vacuum-time=7d  # Keep logs for 7 days
     

2. Check package cache:

   sudo du -sh /var/cache/apt
   

   • Clean it with:

     sudo apt clean
     

3. Check old kernels:

   dpkg --list | grep linux-image
   

   • Remove old ones (except the current):

     sudo apt remove --purge linux-image-OLD-VERSION