Finding Large Files with ncdu

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When a disk suddenly fills up, du can tell you where the space went—but its output is often a long list that is hard to explore. ncdu (NCurses Disk Usage) is a small terminal-based alternative that turns that search into an interactive browser. It scans a directory, sorts folders and files by size, and lets you drill down with the keyboard.

Because it uses the ncurses text interface, ncdu works comfortably over SSH and on machines without a graphical desktop. It is one of those practical tools that is worth having installed before a disk-space emergency.

Install ncdu

On Debian or Ubuntu systems, install it with:

sudo apt install ncdu

On macOS with Homebrew:

brew install ncdu

Other Linux distributions normally provide it through their standard package manager.

Scan the right place

Start by scanning the directory most likely to contain the problem. For example, to inspect your home directory:

ncdu ~

To investigate an application data directory, point ncdu directly at it:

sudo ncdu /var

Avoid beginning with sudo ncdu / unless you really need a whole-machine view. It can take a while, may encounter mounted filesystems you did not intend to scan, and makes it easier to wander into important system files.

After the scan finishes, the largest entries appear first. Use the arrow keys to move, Enter or the right arrow to open a directory, and the left arrow to go back. The displayed size makes it quick to distinguish a genuinely large directory from one that merely contains many small files.

Useful keys include:

  • g — rescan the current directory.
  • n — sort by name instead of size.
  • s — sort by size.
  • d — delete the selected file or directory.
  • q — quit.

The d key is especially convenient when the item is clearly disposable, such as an old download, a build artifact, or an application cache. ncdu asks for confirmation, but deletion is still real: review the path carefully and make sure it is not needed before confirming. For anything important, move or back up the data first instead of deleting it from the disk-usage screen.

A fast cleanup workflow

My usual workflow is to scan the narrowest likely directory first, open the largest entry, and keep drilling down until I find a specific file or cache that explains the usage. Then I either remove it with d, or quit and use a more intentional command if the cleanup needs scripting or a retention policy.

ncdu does not replace backups or careful operational cleanup, but it is an excellent first tool for answering the urgent question: what is using all the disk space? Its interactive ncurses interface makes that answer much easier to find than scrolling through raw disk-usage output.