Using the df command on Linux

The df command provides information on file system usage, but includes quite a few options. This post examines the differences and makes some suggestions about when you should use which of the two commands.

The df command stands for “disk free” and, as that name suggests, it focuses on how much free disk space is available with a clear report like this one:

$ df
Filesystem     1K-blocks    Used Available Use% Mounted on
devtmpfs            4096       0      4096   0% /dev
tmpfs            1939948       0   1939948   0% /dev/shm
tmpfs             775980    1688    774292   1% /run
efivarfs              64      11        48  19% /sys/firmware/efi/efivars
/dev/sda3       13974528 7045364   6330668  53% /
tmpfs            1939948      16   1939932   1% /tmp
/dev/sda3       13974528 7045364   6330668  53% /home
/dev/sda2         996780  305840    622128  33% /boot
/dev/sda1         613160   17780    595380   3% /boot/efi
tmpfs             387988     128    387860   1% /run/user/1000
tmpfs             387988      40    387948   1% /run/user/1001

The default, as you can see from the above output, reports in one kilobyte blocks (1,024 bytes per block) and all file systems are listed. You can ask the command to report on a single file system like this:

$ df /dev/sda3
Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/sda3       13974528 7044600   6331272  53% /

You can also request the information by the name of the mount point. This might make the command a tad easier.

$ df /home
Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/sda3       13974528 7044600   6331272  53% /home

One of the nicest options for this command is to request the data you want to see in a human-friendly format. This would be analogous to telling your old friend that you’re about to celebrate your 17th anniversary, you expect to take two weeks off to celebrate, and you’ll be driving 7 hours to get to the resort where you plan to stay. Reporting all these events in the same unit of time unit would be much harder to communicate. Here’s an example of the report shown above in the human-readable format:

$ 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           758M  1.7M  757M   1% /run
efivarfs         64K   11K   48K  19% /sys/firmware/efi/efivars
/dev/sda3        14G  6.8G  6.1G  53% /
tmpfs           1.9G   16K  1.9G   1% /tmp
/dev/sda3        14G  6.8G  6.1G  53% /home
/dev/sda2       974M  299M  608M  33% /boot
/dev/sda1       599M   18M  582M   3% /boot/efi
tmpfs           379M  128K  379M   1% /run/user/1000
tmpfs           379M   40K  379M   1% /run/user/1001

The df command also provides some other useful options. To report on file system type, for example, you can run a command like this one: