du

Overview

du estimates file space usage for files and directories. Essential for finding what is consuming disk after df shows a full filesystem.

Syntax

du [options] [file...]

Common Options

Option	Description
-h	Human-readable
-s	Summarize (total only)
-a	All files, not just dirs
-c	Grand total
-d n / --max-depth=n	Limit depth
-x	One filesystem
-b	Bytes
--apparent-size	Logical size vs allocated

Examples with Explanations

Top-level breakdown

sudo du -h -d 1 /var 2>/dev/null | sort -h

Largest children of current dir

du -h -d 1 . 2>/dev/null | sort -h | tail

Summary of one tree

du -sh /var/log

Stay on one mount

du -xhd 1 /

Apparent size vs disk usage

du -h file.sparse
du -h --apparent-size file.sparse

Combine with find for huge files

find /var -xdev -type f -size +100M -exec du -h {} + 2>/dev/null | sort -h | tail

Notes & Pitfalls

• Permission denied dirs understate totals without sudo.
• Hard links can double-count depending on options/version.
• Prefer ncdu for interactive exploration when available.

Related Commands

• df — filesystem free space
  
• ls -lS — single directory sizes
  
• ncdu / dust — modern UIs