DF COMMAND

Introduction

In any OS, manage disk space is an important job. In this tutorial, we’ll take a look at how to do this with the df command.

The df command is a powerful utility that we used to see how much space do I have free on the disk. Can use to remember the df command is “Disk-Free”.

Basic Syntax

Let’s understand the basic syntax:

df [OPTION]... [FILE]...

The options parameters influence how the df command interacts with the input. We’ll learn options most important in the upcoming sections. 

The file parameters we set the files we want information or leave blank so we will analyze the entire disk. 

2.1. Default Behavior

When using the only df, it shows all drives.

[root@lostrouter ~]# df
Filesystem                   Size    Used Available Use% Mounted on
devtmpfs                   237760       0    237760   0% /dev
tmpfs                      249332       0    249332   0% /dev/shm
tmpfs                      249332    4580    244752   2% /run
tmpfs                      249332       0    249332   0% /sys/fs/cgroup
/dev/mapper/centos-root  52403200 5690220  46712980  11% /
/dev/sda1                 1038336  170856    867480  17% /boot
/dev/mapper/centos-home  29337604   33076  29304528   1% /home
tmpfs                       49868       0     49868   0% /run/user/0

By default, df shows values in 1-kilobyte blocks.

2.2 Understanding Output

The df command lists too many columns, but the columns name should be self-explanatory:

• Filesystem: The name of each drive. Can be hard drives, logical drives, and virtual drives.
• Size: The size of the filesystem.
• Used: The amount of space used on the filesystem.
• Available: The amount of space free on the filesystem.
• Use%: The percent of space used on the filesystem.
• Mounted on: Show the mount point. The directory where the filesystem is located.

Main Option

Among the available options, some use them very often in our daily. These we can mention:

df -h : Shows disk space in a human-readable format. Display in kilobytes(K), megabytes(M), and gigabytes(G).

[root@lostrouter ~]# df -h
Filesystem               Size  Used Avail Use% Mounted on
devtmpfs                 233M     0  233M   0% /dev
tmpfs                    244M     0  244M   0% /dev/shm
tmpfs                    244M  4.5M  240M   2% /run
tmpfs                    244M     0  244M   0% /sys/fs/cgroup
/dev/mapper/centos-root   50G  5.5G   45G  11% /
/dev/sda1               1014M  167M  848M  17% /boot
/dev/mapper/centos-home   28G   33M   28G   1% /home
tmpfs                     49M     0   49M   0% /run/user/0

df -T : Shows what filesystem type.

[root@lostrouter ~]# df -T
Filesystem              Type     1K-blocks    Used Available Use% Mounted on
devtmpfs                devtmpfs    237760       0    237760   0% /dev
tmpfs                   tmpfs       249332       0    249332   0% /dev/shm
tmpfs                   tmpfs       249332    4580    244752   2% /run
tmpfs                   tmpfs       249332       0    249332   0% /sys/fs/cgroup
/dev/mapper/centos-root xfs       52403200 5690368  46712832  11% /
/dev/sda1               xfs        1038336  170856    867480  17% /boot
/dev/mapper/centos-home xfs       29337604   33076  29304528   1% /home
tmpfs                   tmpfs        49868       0     49868   0% /run/user/0

df -i : Shows free and used inodes.

[root@lostrouter ~]# df -i
Filesystem                Inodes IUsed    IFree IUse% Mounted on
devtmpfs                   59440   335    59105    1% /dev
tmpfs                      62333     1    62332    1% /dev/shm
tmpfs                      62333   442    61891    1% /run
tmpfs                      62333    16    62317    1% /sys/fs/cgroup
/dev/mapper/centos-root 26214400 65045 26149355    1% /
/dev/sda1                 524288   332   523956    1% /boot
/dev/mapper/centos-home 14675968    13 14675955    1% /home
tmpfs                      62333     1    62332    1% /run/user/0

Conclusion

The df command can be very useful for monitor drives usage and shows directories or files that are occupying amounts of space.