Which command is utilized to view overall space usage on a filesystem?

The command utilized to view overall space usage on a filesystem is "df." This command stands for "disk free" and is specifically designed to provide information about the total disk space, used space, available space, and the filesystem’s capacity for mounted filesystems. When executed without any options, it lists the space usage of all mounted filesystems, making it a valuable tool for system administrators who need to monitor disk usage and manage storage efficiently.

In contrast, "du" (disk usage) is used to summarize the disk usage of files and directories rather than providing an overview of the entire filesystem. "ls" is a command for listing directory contents, and while it can display file sizes with the appropriate options, it does not provide filesystem-wide information. "tree" displays the directory structure in a tree-like format, which is useful for visualizing hierarchy but not for checking overall disk space usage. Thus, "df" is the most appropriate choice for assessing overall filesystem space usage.