What is the function of the 'df' command in Linux?

The 'df' command in Linux is primarily used to display disk space usage across different filesystems. When executed, it provides information about the total space, used space, available space, and the filesystem's mount points for each disk partition or filesystem. This is particularly useful for monitoring storage capacity and understanding how much space is occupied by files versus how much is still available for use.

The command presents this data in a user-friendly format, typically in megabytes or gigabytes, allowing users to quickly assess their disk space situation. This functionality is vital for system administration, as it helps in managing storage effectively to avoid running out of disk space, which can lead to system issues.

The other options, while relevant to system information, do not pertain to the 'df' command. File permissions are commonly viewed with commands like 'ls -l', file system types can be examined using 'df -T' or 'mount', and system uptime is displayed with the 'uptime' command.