df command displays the number of free and occupied space on all mounted filesystems systems.
df [options] [filesystem]
-a displays all file systems.
-i displays information about the inode if appropriate organizing drive.
-T displays the file system type.
-t type displays information only about these types of file systems.
-x type eliminates types of file systems from the output data.
-h, –human-readable: print sizes in human readable format (e.g., 1K 234M 2G)
-help displays a help message.
The df command shows the number of free and occupied space in this file system. If you want to know how full of all your disks, type df command with no arguments. In this case, the df command displays information about used and available memory of all currently mounted filesystems systems.