The 'fuser' utility

What is it?

fuser is a command-line utility that detects processes that use a specific file, socket, or file system. It can be useful for troubleshooting issues, killing processes and provides details on the user owning the process and the type of access it has.

Usage

Here are a few examples of using the utility

• To display the process IDs that are using a file:

$ fuser my-filename

• To display the process IDs that are using a mount:

$ fuser -muv /mountpoint

• To terminate all processes that are using a specific file or port:

$ fuser -k filename
$ fuser -k 8080/tcp

• To see the process IDs that are using a particular TCP or UDP port:

$ fuser -v -n tcp 443
$ fuser -v -n udp 111

To see a full list of flags and what else the fuser utility is capable of, please refer to the manual (man page) man fuser 

Notes

fuser requires special permissions (e.g., root access) to display processes owned by other users.