fuser
A command-line utility that identifies which processes are using specific files, sockets, or directories on a Linux system.
fuser is useful for determining process ownership of open files and network resources. It helps troubleshoot permission issues, identify which program holds a lock on a file, or find processes listening on a network port.
Common usage examples:fuser /home — shows which processes have files open in /homefuser -n tcp 8080 — identifies processes using TCP port 8080fuser -k /mnt/usb — terminates all processes accessing /mnt/usb (useful before unmounting)
The output displays process IDs (PIDs) by default, with optional letters indicating access type: c (current directory), e (executable), f (open file), r (root directory), or m (memory-mapped file).