How to understand what's taking up disk space?

If you want a command-line tool, I prefer ncdu, an ncurses version of du. It scans the disk (or a given folder) and then shows the top-level space usages; you can select a given directory to get the corresponding summary for that directory, and go back without needing to reanalyze:

If you’re ok with a GUI program, Filelight is the closest thing to WinDirStat I’ve found; it shows a graphical view of space consumption:

Like ncdu, Filelight lets you select a given directory to get the breakdown for that directory

Another GUI program is: baobab

There’s also this cool python script from /www.vrplumber.com/programming/runsnakerun/

bzr branch lp:~mcfletch/squaremap/trunk squaremap

It’s not the most feature rich, but it’s run from a single python script so it’s extremely portable.

You should be aware that WinDirStat is actually a port of KDirStat, which is a Linux/KDE program. So, if you are looking for a Linux alternative to WinDirStat, you certainly should take a look at KDirStat. It is already packaged in most distros, just install it.

Another alternative is FileLight, already cited by Michael Mrozek, and the Konqueror plugin fsview (you can run it standalone from the command-line).

You could also try GD Map, another GUI tool based on treemaps.

I have recently used command line tool (CLI, not TUI): http://zevv.nl/play/code/philesight/

It produces a PNG file which you can view somewhere else. It also has a CGI script.

Most likely you are not limited to text mode at your local workstation, so it should be appropriate.

If you looked at the about screen on windirstat it showed you that it’s based on kdirstat.

http://kdirstat.sourceforge.net/

I prefer the following command line:

$  du -s -m -x * | sort -n

Breaking it down, du shows disk usage; -s says print the total for each argument (each item in the current directory), -m says show the size in Megabytes. This makes it easier for sort to work; sort doesn’t really understand the -h output. The -x ignores other filesystems; this is useful when trying to find space hogs in /var, and /var/spool/foo is a different filesystem.

Also to see the files in a specific directory sorted by size after you have found the directory using du use:

ls -lrSh

Use QDirStat (formerly KDirStat).

It includes a perl script that generates a cache file on the server/console without any need for an UI to be running/installed; transfer it to your desktop machine and view it in the gui client.

See https://unix.stackexchange.com/a/256516/186308 for details.

xdiskusage is very flexible, lightweight with very lean dependencies, easy to compile..

It shows a tree left-to-right that you can navigate with mouse or arrow keys, zoom in (click or enter), hide some parts for a better view, change sort order, number of colors etc with keys or context menu.

It’s so lighweight that you can use it on a remote SSH link with good performance. In this case I recommend -q command line option to disable the progress bar that appears while files are walked.

You can also optionally run du yourself beforehand.

One situation is a remote filesystem which is full or near-full. On that system run du -ak | gzip >log_of_disk_usage.txt.gz, fetch the output and run gzip -dc log_of_disk_usage.txt.gz | xdiskusage -aq locally.
Or even ssh myremotesystem "cd /filesystem_near_full/ ; du -ak | gzip" > log_of_disk_usage.txt.gz to store the result locally without writing anything remotely.

xdiskusage does not offer to modify the filesystem (like move to trash, etc) but you can copy a path to clipboard and paste that into a file manager, terminal etc.

Duc (https://duc.zevv.nl/) will work from the command line.

It can be installed and used like this in Debian 9:

# apt install duc
# duc index /
# duc graph /

With this you’ll get a file named duc.png in the current directory. Now, you can copy this file to another GUI capable computer and it will look like this:

NOTE: Duc is the replacement for the tool that @OCTAGRAM mentioned in his answer.

For btrfs filesystems, you may like my tool, btdu:

• Starts showing results instantly
• Shows snapshots / reflinks / cloned files correctly
• Shows real (compressed) usage of compressed files