Linux DU and DF Result Differences

This is something I’ve run into a few times. I’ll pull up a `df -h` command and see something where the root directory (or /var or /usr) or something is filled up completely, and I try to locate where the space is with a `du -xh --max-depth=1 /directory_that_is_full` and the result shows me something completely different than the `df -hl`. What I’ve found, this is something to do with a conflict of a process trying to access a file...