Checking Disk Usage in Linux

I had to find out much free space was available on a file system on a Linux server. Now getting this information on the GUI is simple - a few clicks, modals and stuff, but the server doesn't have a GUI so it's off to the terminal I go 😋

The other scenario I faced was figuring out the disk usage of certain files and directories.

I accumulated a bunch of commands through co-workers and Google, jotted them down and decided that this post will be my research and cheat sheet. I hope future me and you can benefit from this.

This post forms part of a sequence of command line references that I will be writing where I forget the command or its syntax or find it interesting enough to document.

Although it is easily Google-able, there are usually a chain of commands that I want kept together for reference.

The commands I use should be universal but just in case, I am running Fedora release 28 (Twenty Eight) and Zsh. Sometimes I will refer to server commands in which case I will specify the server OS.

Also, if you want to contribute something interesting in any of my posts, please create a pull-request or write a comment below. 😄

Just so by the way, I find this freakin' awesome:
Use -- -x to grep anything starting with a -. I find this useful when looking up switches for programs in their manuals man sudo | grep -- -u.

A more efficient way is to man sudo press / enter your search phrase, press n for next until you find your switch. You can read everything about the switch instead of one line.

Getting disk space for your file system

df will show you the amount of disk space available on your file system.

Blocks

1K-blocks     Used Available Use%
  8145968        0   8145968   0%

Disk space is shown in 1K blocks unless its overridden when the environment variable POSIXLY_CORRECT is set. Then 512 byte blocks are used.

By the way, according to the GNU standards: "GNU utilities mostly follow specifications of POSIX.2. POSIX.2 specifies that df and du must output sizes by default in units of 512 bytes. What users want is units of 1K, so that is what we do by default. If you want the ridiculous behavior “required” by POSIX, you must set the environment variable POSIXLY_CORRECT (which was originally going to be named POSIX_ME_HARDER)."

Sizes

You can print sizes in a more human friendly way using the -h switch.

df -h

Size  Used Avail Use%
7.8G     0  7.8G   0%

Usage reports

Local mounted file systems

When you run df -h you will get a usage report on all mounted file systems with human readable sizes.

The -l switch will only print local file systems which excludes any remote file systems.

df -lh

➜  resources  ➜ df -lh
Filesystem               Size  Used Avail Use% Mounted on
devtmpfs                 7.8G     0  7.8G   0% /dev
tmpfs                    7.8G  178M  7.7G   3% /dev/shm
tmpfs                    7.8G  2.0M  7.8G   1% /run
tmpfs                    7.8G     0  7.8G   0% /sys/fs/cgroup
/dev/mapper/fedora_root   49G   18G   29G  38% /
tmpfs                    7.8G   15M  7.8G   1% /tmp
/dev/sda1                976M  242M  668M  27% /boot
/dev/mapper/fedora_home  976G   68G  859G   8% /home
tmpfs                    1.6G   16K  1.6G   1% /run/user/42
tmpfs                    1.6G  8.5M  1.6G   1% /run/user/1000

You can pass in paths and file names as arguments. You will get the disk space available for the file systems each one is on.

df -lh / ~

➜  ~ ➜ df -lh / ~
Filesystem               Size  Used Avail Use% Mounted on
/dev/mapper/fedora_root   49G   18G   29G  39% /
/dev/mapper/fedora_home  976G   80G  847G   9% /home

Pseudo, duplicate and inaccessible file systems

There are also pseudo, duplicate and inaccessible file systems. You can get information on all of them using the all -a switch.

df -lah

➜  resources  ➜ df -lah
Filesystem                Size  Used Avail Use% Mounted on
sysfs                        0     0     0    - /sys
proc                         0     0     0    - /proc
devtmpfs                  7.8G     0  7.8G   0% /dev
securityfs                   0     0     0    - /sys/kernel/security
tmpfs                     7.8G  2.0M  7.8G   1% /run
tmpfs                     7.8G     0  7.8G   0% /sys/fs/cgroup
/dev/mapper/fedora_root    49G   18G   29G  38% /
tmpfs                     7.8G   14M  7.8G   1% /tmp
/dev/mapper/fedora_home   976G   80G  847G   9% /home
...

Pseudo file systems keep information about "pretend" file systems. It contains virtual entries which exist in RAM so it does not persist on reboots. Examples include /proc which is a procfs and dynamically generates directories for each process. /sys generates hardware layout for physical devices in the machine in a bunch of files and directories.

Getting disk usage for files and directories

Usage estimation

du estimates the disk usage of a bunch of files and directories that you choose. It will recursively calculate the usage of directories for you. The below command will operate on the current working directory.

du -h

➜  public  ➜ du -h
20K     ./html
28K     ./public/img
4.0K    ./public/js
8.0K    ./public/css
48K     ./public
8.0K    ./docs
80K     .

The -s switch will only print out the summary of disk space used by each file and directory.

du -hs

➜  public  ➜ du -hs
80K     .

You can pass in paths to directories and files to the get estimated disk usage for them. With -a you will get all files, not just directories.

du -ah logos fonts

➜ public ➜ du -ah logos fonts
8.0K    logos/logo.png
4.0K    logos/128x128.png
 20K    logos/512x512.png
4.0K    logos/64x64.png
4.0K    logos/32x32.png
 44K    logos
4.0K    fonts/timeline.ttf
8.0K    fonts/timeline.svg
 12K    fonts/selection.json
4.0K    fonts/timeline.woff
4.0K    fonts/timeline.eot
 36K    fonts

du takes a shell pattern argument. This is not a regular expression.
> • ? matches a single character.
> • * matches any string.

Examples of how to use the file name shell pattern:

• file.?ar will return files where the extension ends with a three letter extension ending in ?ar like tar and rar

• *.json will return all json files which you could also exclude using --exclude="*.json"

Below I want all files excluding html and txt files.

du -hs * --exclude="*.html" --exclude="*.txt"

➜  public ➜ du -hs * --exclude="*.html" --exclude="*.txt"
4.0K	favicon.png
36K	    fonts
13M	    images
44K	    logos

Sorting results

You can sort the output in reverse (-r) numerical order (-n) plus you can page through the results (less).

du -h | sort -rn | less

➜  resources  ➜ du -h | sort -rn | less
80K     .
48K     ./public
28K     ./public/img
20K     ./html
8.0K    ./public/css
8.0K    ./docs
4.0K    ./public/js

Futhermore, you can print out 1 to the nth results. This includes the summary as it is part of the result set.

du -h | sort -rn | head -n 3

➜  resources  ➜ du -h | sort -rn | head -n 3
80K     .
48K     ./public
28K     ./public/img

Listing directories and files with their size

Using the ls utility

You can page through a column of all files and directories which include multiple attributes including the file size. This will include hidden files such as your dotfiles.

ls -lah | less

➜  imgs ➜ ls -lah | less
total 48K
drwxrwxr-x. 2 clarice clarice 4.0K Jan 12 06:05 .
drwxrwxr-x. 7 clarice clarice 4.0K Jan 12 06:05 ..
-rw-------. 1 clarice clarice 3.8K Jan 12 06:05 128x128.png
-rw-------. 1 clarice clarice  989 Jan 12 06:05 32x32.png
-rw-------. 1 clarice clarice  20K Jan 12 06:05 512x512.png
-rw-------. 1 clarice clarice 1.9K Jan 12 06:05 64x64.png
-rw-------. 1 clarice clarice 6.8K Jan 12 06:05 logo.png

Note that there is a total on the top left showing how much space is being used.

Sorting

Use -S to sort by file size. The largest file size will be printed first. -r will reverse the sorting order.

ls -lahS

ls -lahSr

Recursive listing

Recursive directories are not supported by default. To list recursively add the -R switch but beware.

The buffer! Yeah, if you chose to run this command on / or any large project, you might not be able to see all your results. You could write your results to a file if you really need this information ls -lahR > space.out. If you notice that it is taking too long then you can tail -f space.out

ls -lahR

ls -lahR > space.out

tail -f space.out

Using the tree utility

tree is a utility that needs to be installed. It will recursively iterate and list your files in a really cool colored tree-like structure. No colors in the examples though 😔, so go on - use it. 😛

➜  public ➜  tree
.
├── favicon.png
├── fonts
│   ├── selection.json
│   ├── timeline.eot
│   ├── timeline.svg
│   ├── timeline.ttf
│   └── timeline.woff
├── google484846af030102e2.html
├── images
│   └── profile.jpg
├── index.html
├── logos
│   ├── 128x128.png
│   ├── 32x32.png
│   ├── 512x512.png
│   ├── 64x64.png
│   └── logo.png
├── manifest.webmanifest
├── render-page.js.map
└── robots.txt

You can add file sizes to the tree by adding -s and combine it with -h to print out the human friendly file size next to each file and directory.

tree -sh

➜  public ➜ tree -sh
.
├── [ 1.9K]  favicon.png
├── [ 4.0K]  fonts
│   ├── [ 9.6K]  selection.json
│   ├── [ 2.9K]  timeline.eot
│   ├── [ 6.0K]  timeline.svg
│   ├── [ 2.8K]  timeline.ttf
│   └── [ 2.8K]  timeline.woff
├── [   53]  google484846af030102e2.html
├── [ 4.0K]  images
│   └── [  35K]  profile.jpg
├── [ 1.7K]  index.html
├── [ 4.0K]  logos
│   ├── [ 3.8K]  128x128.png
│   ├── [  989]  32x32.png
│   ├── [  20K]  512x512.png
│   ├── [ 1.9K]  64x64.png
│   └── [ 6.7K]  logo.png
├── [  344]  manifest.webmanifest
├── [  97K]  render-page.js.map
└── [  122]  robots.txt

Cheat sheet

Grep anything starting with -

man sudo | grep -- -u

Disk usage on file systems

With human-readable sizes on all mounted file systems

df -h

Local file systems only

df -lh

For the file system each path/file specified is on

df -lh / ~

For pseudo, duplicate and inaccessible file systems

df -lah

Disk usage of files

Get estimated usage with human-readable sizes

du -h

Get a summary of disk space used

du -hs

Get all files for a give path

du -ah public/logos

Exclude files

du -hs * --exclude="*.html" --exclude="*.txt"

Sort

du -h | sort -rn | less

Get the top three sorted results

du -h | sort -rn | head -n 3

Listing directories and files using ls

Get a paged list of files and directories

ls -lah | less

Sort the results by file size

ls -lahS | less

Reverse the sorted results

ls -lahSr | less

Recursively list files and directories

ls -lahR

Print the output of a recursive list to a file

ls -lahR > space.out

Watch a file while it is being printed to

tail -f space.out

List a tree of files and directories with file sizes

tree -sh

Resources

• man du
• man df
• man tree
• man ls
• Non-GNU Standards - gnu.org
• Differences between df, df-h and df -l - askubuntu
• What is a pseudo file system in Linux? - StackExchange
• Useful "df" Commands to Check Disk Space in Linux