fuser

Display process IDs currently using files or sockets.

Find which processes are accessing a file or directory:

fuser {{path/to/file_or_directory}}

Show more fields (USER, PID, ACCESS and COMMAND):

fuser --verbose {{path/to/file_or_directory}}

Identify processes using a TCP socket:

fuser --namespace tcp {{port}}

Kill all processes accessing a file or directory (sends the SIGKILL signal):

fuser --kill {{path/to/file_or_directory}}

Find which processes are accessing the filesystem containing a specific file or directory:

fuser --mount {{path/to/file_or_directory}}