The focus of this article will be on how you can check the disk usage of Linux systems from the command line. The command used to estimate disk usgae is the du command, short for disk usage. The du command is part of the GNU Core Utilities and available on all Linux and UNIX systems.

The du command can be used on directories or files. By default it will check and output disk usage for directories (not file size). It is important to know the difference in order to get the information you need quickly.

Disk Usage vs File Size

The du command shows you disk usage, which is different than file size. It shows you multiples of the filesystem block size. A particular files may be smaller, if it does not use a complete block. The ls command on the other hand shows apparent size of a file. Although the du command has an option to show apparent size (more on that below), we recommend using the ls command for files and the du command for directories.

The apparent size of a file is how much data is contains. Block-oriented devices (hard drives, SSD, etc..) work by storing data in fixed-size blocks. As a file is written to a block device, there may be a block that is not completely filled. As a result, disk usage (as reported by du) is rounded up to the highest amount of blocks used. This is a simplification, but block devices and file systems are outside the scope of this tutorial.

Basic Usage of the du Command

Using the du command without any options will recursively check every directory and sub-directory in the current working directory. The output displays each directory disk usage and path, with a total disk usage at the end. In this example is shows the total followed by a dot (noting the current working directory) since we did not specify a directory.

[[email protected] ~]$ du
5996	./.cache/gnome-software/appstream
8	./.cache/gnome-software/langpacks
4	./.cache/gnome-software/fwupd/remotes.d/lvfs
8	./.cache/gnome-software/fwupd/remotes.d
92	./.cache/gnome-software/fwupd
...
4	./Downloads
4	./Pictures
72	./.pki/nssdb
76	./.pki
4	./Desktop
714356	.

The du Command Options

The du command provides a lot of options for expanding it’s usefulness. Here we will outline some of the most popular options with examples.

Display Sizes in Human Readable Format

The default output units are not very friendly to humans. By using the -h (–human-readable) option we can display the sizes in a much more friendly format (e.g. 4K, 59M, 3G)

[[email protected] ~]$ du -h .
5.9M	./.cache/gnome-software/appstream
8.0K	./.cache/gnome-software/langpacks
4.0K	./.cache/gnome-software/fwupd/remotes.d/lvfs
8.0K	./.cache/gnome-software/fwupd/remotes.d
92K	./.cache/gnome-software/fwupd
...
4.0K	./Downloads
4.0K	./Pictures
72K	./.pki/nssdb
76K	./.pki
4.0K	./Desktop
698M	.

Get Summary of Directory Size Only

It is seldom useful to see a giant list of files. You can use the -s (–summarize) option to display ONLY the total size of the directory.

[[email protected] ~]$ du -s
714356	.

Display the Size of Directory in KB or MB

You can also decide to display disk usage size in Kb or MB.

To accomplish this simply use k for kilobytes, and -m for megabytes.

[[email protected] ~]$ du -k Videos/
861872	Videos/YouTube
17176	Videos/Intros
60620	Videos/Snippets
939672	Videos/

Example using -m for MB:

[[email protected] ~]$ du -m Videos/
842	Videos/YouTube
17	Videos/Intros
60	Videos/Snippets
918	Videos/

Show All Files and Directories

As you may have noticed, these commands only display the disk usage of the directories, not the files. To display the files as well, use the -a (–all_ flag as shown.

[[email protected] ~]$ du -ah Videos/
235M	Videos/YouTube/bash-hash-table-explained.mp4
87M	Videos/YouTube/timeout-command.mp4
496M	Videos/YouTube/ClusterSSH-Youtube.mp4
26M	Videos/YouTube/SteamLocomotive-sl.mp4
842M	Videos/YouTube
9.1M	Videos/Intros/Putorius-Intro-No-Tagline.mp4
7.7M	Videos/Intros/Putorius-Intro-Short-w-Tagline-v2.mp4
17M	Videos/Intros
13M	Videos/Snippets/tags-file.mp4
9.1M	Videos/Snippets/using-admin-console.mp4
7.1M	Videos/Snippets/main-config.mp4
12M	Videos/Snippets/clusters-file.mp4
4.6M	Videos/Snippets/auto-build-config.mp4
16M	Videos/Snippets/basic-usage-no-config.mp4
60M	Videos/Snippets
918M	Videos/

NOTE: Don’t forget to subscribe to our YouTube channel for video tutorials!

Find Total Directory Usage

To show a grand total of all the disk usage you can use the -c (–total) option.

[[email protected] ~]$ du -c Videos/
861872	Videos/YouTube
17176	Videos/Intros
60620	Videos/Snippets
939672	Videos/
939672	total

This is very similar to the summarize (-s) option. The main difference being that summarize will show ONLY the total, and -c (–total) will still show the full output.

[[email protected] ~]$ du -c Videos/
861872	Videos/YouTube
17176	Videos/Intros
60620	Videos/Snippets
939672	Videos/
939672	total

[[email protected] ~]$ du -s Videos/
939672	Videos/

Show Apparent File Size with du Command

To show the apparent size (actual data size) of a file you can use the –apparent-size option.

[[email protected] YouTube]$ du ClusterSSH-Youtube.mp4 
507152	ClusterSSH-Youtube.mp4

[[email protected] YouTube]$ du --apparent-size ClusterSSH-Youtube.mp4 
507146	ClusterSSH-Youtube.mp4

In the above example, you can see the apparent file size is slightly smaller than the size reported by du. The –apparent-size output is more in line with what the ls command would report.

Limiting Directory Level or Depth

If you have a lot of directory depth (sub-directories inside sub-directories) you may want to limit the depth that du will go. Using the –max-depth option you can specify how far down the directory tree du will plunge.

For this example, let’s say we have the following directory tree.

[[email protected] Documents]$ tree ~/Documents/
/home/mcherisi/Documents/
└── Recipes
    └── Italian
        └── Pizzaiola
            └── Steak

We can instruct the du utility to only go two levels deep like so:

[[email protected] Documents]$ du --max-depth=2
12	./Recipes/Italian
16	./Recipes
20	.

Here is an example using max depth 1 through 4 to better illustrate how it works.

[[email protected] Documents]$ du -d 1
16	./Recipes
20	.
[[email protected] Documents]$ du -d 2
12	./Recipes/Italian
16	./Recipes
20	.
[[email protected] Documents]$ du -d 3
8	./Recipes/Italian/Pizzaiola
12	./Recipes/Italian
16	./Recipes
20	.
[[email protected] Documents]$ du -d 4
4	./Recipes/Italian/Pizzaiola/Steak
8	./Recipes/Italian/Pizzaiola
12	./Recipes/Italian
16	./Recipes
20	.

Showing Hidden Files with the du Command

Unfortunately, du does not have an option to show hidden files. Here is a little work-around to show hidden files.

[[email protected] ~]$ du -sm .[!.]* *
1	.bash_history
1	.bash_logout
1	.bash_profile
1	.bashrc
37	.cache
...OUTPUT TRUNCATED...

Combining Options and Piping Output

As with most Linux commands you can combine the options to further specify the desired information in the output. You can also pipe the output to other utilities to further refine the output. Here are some examples.

Get Summarized Grand Total in Human Readable Format

By combining these three options we can get very specific information.

[[email protected] ~]$ du -csh ~/Videos/
918M	/home/mcherisi/Videos/
918M	total

Sort Largest Sub-Directories

We can pipe the output to sort so list the sub-directories that are using the most disk space in order from largest to smallest.

[[email protected] Documents]$ du -h -d1 ~/Videos/ | sort -hr
918M	/home/mcherisi/Videos/
842M	/home/mcherisi/Videos/YouTube
60M	/home/mcherisi/Videos/Snippets
17M	/home/mcherisi/Videos/Intros

Conclusion

The du command is a very mature tool and has a good deal of options to expand it’s usefulness. We covered most of the popular options here, but there are several more. Check the man page for all the options available. However, after reading this article, you should be comfortable with using the du command to find the disk usage of your system.

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