How to Check Disk Space on Linux

Checking Disk Space on Linux

Running out of disk space on Linux can crash services and prevent logins. These commands let you see where your space is going at a glance.

df — Check Filesystem Usage

df shows how full each mounted filesystem is. Always use the -h flag for human-readable sizes:

df -h

Sample output:

Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1        50G   22G   26G  46% /
tmpfs           2.0G     0  2.0G   0% /dev/shm

Focus on the Use% column. Anything above 85% needs attention.

du — Check Directory Sizes

du summarizes disk usage for files and directories. The most useful form is:

du -sh /*

This shows the total size of every top-level directory. To find the biggest directories under a specific path:

du -h --max-depth=1 /var | sort -rh | head -10

sort -rh sorts by human-readable size, largest first. head -10 shows only the top 10.

ncdu — Interactive Disk Usage Browser

ncdu is a terminal-based, interactive version of du. Install it first:

# Ubuntu/Debian
sudo apt install ncdu

# Fedora
sudo dnf install ncdu

Run it on a directory:

ncdu /

Use the arrow keys to navigate into folders and press d to delete items. It is the fastest way to find and remove large files.

Common Space Hogs to Check

• /var/log — log files that grow over time
• /var/cache/apt — old package downloads (clear with sudo apt clean)
• /tmp — temporary files
• ~/Downloads and ~/.local/share/Trash — user-level junk
• Docker images: docker system prune -a can free gigabytes

Quick Reference

• df -h — overall filesystem usage
• du -sh /path — size of a specific directory
• du -h --max-depth=1 /var | sort -rh | head -10 — top 10 subdirectories
• ncdu / — interactive browser (install separately)
• sudo apt clean — free apt cache