Which command checks disk space usage of a filesystem?

The command that checks disk space usage of a filesystem is 'df -h'. This command provides an overview of the disk space available and used on all mounted filesystems. The '-h' option formats the output in a human-readable form, displaying sizes in KB, MB, or GB, making it easier for users to quickly assess how much space is available or used.

The 'du' command, while it also deals with disk usage, focuses on the disk usage of files and directories, not on overall filesystem capacity. On the other hand, 'lsblk' is used to list information about all available block devices, showing their mount points and sizes but not detailing disk space usage. Finally, 'fdisk -l' is a command for listing partition tables and does not provide information about the disk space utilization of those partitions. Therefore, 'df -h' is the appropriate choice for checking the comprehensive disk space usage of a filesystem.