36.2. User Accessing Files: fuser

It can be useful to determine what processes or users are currently accessing certain files. Suppose, for example, you want to unmount a file system mounted at /mnt. umount returns "device is busy." The command fuser can then be used to determine what processes are accessing the device:

$ fuser -v /mnt/*

                     USER        PID ACCESS COMMAND
                     jj        26597 f....  less

Following termination of the less process, which was running on another terminal, the file system can successfully be unmounted.

SUSE LINUX Administration Guide 9.3