Which command displays the current disk space usage for all mounted file systems?

The command that displays the current disk space usage for all mounted file systems is 'df'. This command stands for "disk free" and provides a summary of the available and used disk space for each mounted file system. It shows information such as total size, used space, available space, and the mount points of filesystems.

Using 'df' without any options gives a clear overview of how much disk space each partition is consuming, making it a very useful tool for system administrators who need to monitor disk usage in a Linux environment.

Other commands, like 'du', are used for different purposes. The 'du' command is designed to estimate file and directory space usage, providing details about the size of individual directories or files rather than overall mounted file systems. The 'lsblk' command lists block devices but does not show disk usage statistics directly. Lastly, 'diskusage' is not a standard command in Linux for checking disk space and would not be recognized in most distributions. Thus, 'df' is the most appropriate choice for displaying current disk space usage for all mounted file systems.