lsof

• umount /home device is busy

To see all Open files

lsof

To see all network activity

lsof -i

See the connections on port 80

lsof -i :80

To see all files opened by a process

lsof -p PID

To see all files opened by a process and refresh it every 5 seconds, run

lsof -p PID_HERE -r 5

See Linux Commands