Why does the command still show the section as filled after data deletion, despite clearing?

Even after deleting files from a directory, the df command may still show that space is not freed if:

• Files were deleted, but processes still hold open file descriptors to those files. In this case, the data remains on disk until all descriptors are closed.
• Files are in hidden or mounted points that are not directly visible.

To check open files, you can use:

lsof +L1

This will show deleted but still open files. To free space, you need to terminate processes holding them or reboot the system.