Linux Command: du

du (disk usage) estimates file and directory space usage. Unlike df which shows filesystem-level usage, du shows how much space individual directories and files consume. du is the go-to tool for finding what is consuming disk space. Combined with sort, it quickly identifies the largest directories and files. The -s flag gives directory totals, and -h makes output human-readable. du reads actual disk usage (allocated blocks), not file sizes. A 1-byte file still uses one disk block (typically 4KB).

Syntax

du [OPTION]... [FILE]...

Key Options

• -h — Human-readable sizes
• -s — Show only total for each argument
• -a — Show all files, not just directories
• -c — Show grand total
• --max-depth — Limit directory depth
• -x — Stay on same filesystem

Examples

Find largest directories

du -sh /home/* | sort -rh | head -10

Output: 50G\t/home/developer\n12G\t/home/admin\n2G\t/home/guest

Directory summary

du -sh /var/log/ /var/www/ /tmp/

Output: 2.5G\t/var/log/\n15G\t/var/www/\n500M\t/tmp/

First level breakdown

du -h --max-depth=1 / 2>/dev/null | sort -rh | head

Output: 50G\t/var\n20G\t/home\n5G\t/usr

Pro Tips

• This one-liner quickly shows the largest items in the current directory, sorted by size. Essential for disk cleanup.
• du shows actual disk usage (allocated blocks). ls -l shows file size. A sparse file may show 1GB in ls but 0 in du.
• du traverses all files. On large filesystems, du / can take minutes. Use ncdu for interactive, cached exploration.

Learn more: Full du reference →