What is the role of the command df in Linux?

The command used in Linux known as 'df' primarily shows the amount of disk space used and available on the file systems. It provides a report of the disk space usage for each mounted filesystem, typically along with details such as the total size, used space, available space, and the mount point of each partition. This information is critical for system administrators and users in monitoring and managing disk space effectively.

The other options relate to different functionalities in Linux. For instance, mounting virtual directories involves commands like 'mount' rather than 'df', which focuses solely on displaying filesystem information. Changing filesystem labels is done using commands like 'tune2fs' or 'e2label', while unmounting filesystems is accomplished with the 'umount' command. Understanding the specific purpose of 'df' helps in effectively utilizing command-line tools for system management.