Examining disk space on Linux

There are many ways to evaluate disk space usage on Linux, and this post examines a number of commands that allow you to view used and available disk space.

Using the df (disk free) command

The df command stands for “disk free” and, as that name suggests, it focuses on how much free disk space is used and how much is available. By default, the command reports disk usage in kilobytes.

# df
Filesystem     1K-blocks     Used Available Use% Mounted on
devtmpfs            4096        0      4096   0% /dev
tmpfs            1937768        0   1937768   0% /dev/shm
tmpfs             775108     1712    773396   1% /run
efivarfs              64       23        37  39% /sys/firmware/efi/efivars
/dev/sda3       13974528 11385772   1873284  86% /
/dev/loop0        106496   106496         0 100% /var/lib/snapd/snap/core/16928
/dev/loop1          8704     8704         0 100% /var/lib/snapd/snap/gping/13
tmpfs            1937768       16   1937752   1% /tmp
/dev/sda2         996780   250032    677936  27% /boot
/dev/sda1         613160    19484    593676   4% /boot/efi
/dev/sda3       13974528 11385772   1873284  86% /home
tmpfs             387552      132    387420   1% /run/user/1000
tmpfs             387552       44    387508   1% /run/user/1001

Used with the -h option, df reports in the “human-readable” format, adjusting the data to report in megabytes, kilobytes or gigabytes as appropriate.

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
devtmpfs        4.0M     0  4.0M   0% /dev
tmpfs           1.9G     0  1.9G   0% /dev/shm
tmpfs           757M  1.7M  756M   1% /run
efivarfs         64K   23K   37K  39% /sys/firmware/efi/efivars
/dev/sda3        14G   11G  1.8G  86% /
/dev/loop0      104M  104M     0 100% /var/lib/snapd/snap/core/16928
/dev/loop1      8.5M  8.5M     0 100% /var/lib/snapd/snap/gping/13
tmpfs           1.9G   16K  1.9G   1% /tmp
/dev/sda2       974M  245M  663M  27% /boot
/dev/sda1       599M   20M  580M   4% /boot/efi
/dev/sda3        14G   11G  1.8G  86% /home
tmpfs           379M  132K  379M   1% /run/user/1000
tmpfs           379M   44K  379M   1% /run/user/1001

Superuser access is not required to check disk space using the df command unless you need to look into directories for which you don’t have read access. Note that, in the command below, I can ask about george’s home directory, but not about its contents.

$ df /home/george
Filesystem     1K-blocks     Used Available Use% Mounted on
/dev/sda3       13974528 11385960   1873096  86% /home
$ df /home/george/report
df: /home/george/report: Permission denied

The df command with the -T option displays the partition and file system type for the selected directory.

$ df -T /home
Filesystem     Type  1K-blocks     Used Available Use% Mounted on
/dev/sda3      btrfs  13974528 11386752   1872304  86% /home

Using the du (disk usage) command

The du command reports on disk usage but, if you run this command in your home directory, it will report on every file. To view overall disk usage, run a command like this:

$ du -sk
144200  .

The number above represents the size of the current directory. The dot simply represents the current location. A command like that shown below reports the same data.

$ du -sk /home/shs
144200  /home/sh

Notice that using the -sk options, you also don’t see details on subdirectories.

$ du bin
12      bin/NOTES
24      bin
$ du -sk bin
24      bin

Superuser access is required if you want to report on directories for which you don’t have adequate permission.

# du -sk *
24      cookie
16      dumdum
431784  fedora
32      george
48      lola
16      newuser
144200  shs

Like df, du has an option for the “human-readable” format.

$ du -h bin
12K     bin/NOTES
24K     bin

Use the du -sh command to show the size of your current directory.

$ du -sh .
141M    .

Directories for which you don’t have read access will be obvious and the sum shown will not reflect their contents. The last line in the output below lists the size of the current directory.

$ cd /home; du -sh .
du: cannot read directory './fedora': Permission denied
du: cannot read directory './newuser': Permission denied
du: cannot read directory './george': Permission denied
du: cannot read directory './lola': Permission denied
du: cannot read directory './dumdum': Permission denied
du: cannot read directory './cookie': Permission denied
141M    .

A command like that below will display disk usage for the largest files or directories in the current file system location.

$ du -ah /home/shs | sort -rh | head -n 5
141M    /home/shs
115M    /home/shs/.cache
48M     /home/shs/.cache/gnome-software
46M     /home/shs/.cache/mozilla/firefox/c8n9kgaz.default-release
46M     /home/shs/.cache/mozilla/firefox

Using the ls command

The ls command generally lists files by name, but it can also display files in size order with the -lhS options.

$ ls -lhS | head -5
total 708K
-rw-r--r--. 1 shs    shs    3.9K Nov  8  2023 bash_builtins
-rw-r--r--. 1 shs    shs    2.5K Nov 17  2023 AllTables
drwxr-xr-x. 1 shs    shs    1.9K Jan  2 12:38 videos
-rwx------. 1 shs    shs    1.7K Nov 27  2023 buildTable

And don’t forget that you can turn commands like this into aliases to make them easier to use.

$ alias bysize="ls -lhS"

Using the fdisk command

The fdisk command can provide useful stats on your disk partitions. Here’s an example:

$ sudo fdisk
fdisk: bad usage
Try 'fdisk --help' for more information.
$ sudo fdisk -l
Disk /dev/sda: 14.91 GiB, 16013942784 bytes, 31277232 sectors
Disk model: KINGSTON SNS4151
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 818C0FC9-CBBA-49E5-953B-A511A4E40A3D

Device       Start      End  Sectors  Size Type
/dev/sda1     2048  1230847  1228800  600M EFI System
/dev/sda2  1230848  3327999  2097152    1G Linux filesystem
/dev/sda3  3328000 31277055 27949056 13.3G Linux filesystem

Disk /dev/zram0: 3.7 GiB, 3967811584 bytes, 968704 sectors
Units: sectors of 1 * 4096 = 4096 bytes
Sector size (logical/physical): 4096 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/loop0: 103.99 MiB, 109043712 bytes, 212976 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk /dev/loop1: 8.44 MiB, 8847360 bytes, 17280 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

Using the lsblk command

The lsblk command provides very useful information on your disk partitions. The output shown below clearly shows that the disk (sda) had three partitions and their sizes and mount points.

$ lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
loop0    7:0    0  104M  1 loop /var/lib/snapd/snap/core/16928
loop1    7:1    0  8.4M  1 loop /var/lib/snapd/snap/gping/13
sda      8:0    0 14.9G  0 disk
├─sda1   8:1    0  600M  0 part /boot/efi
├─sda2   8:2    0    1G  0 part /boot
└─sda3   8:3    0 13.3G  0 part /home
                                /
zram0  252:0    0  3.7G  0 disk [SWAP]

Wrap-up

These commands described in this post can help you evaluate disk storage, diagnose disk usage issues and manage disk space effectively.

Related reading:

• Linux commands for managing, partitioning, troubleshooting
• Examining partitions on Linux systems
• How to use the fdisk command
• How to use the du command
• Tracking disk space usage