How do I unlock a folder/file under Linux

Question

Today I had the problem that I couldn't delete a folder because "it was busy".

How can I find out which application to blame for that or can I just delete it with brute force?

Answer 1

Use lsof to find out what has what files are open.

man lsof or have a look here

Answer 2

The fuser Unix command will give you the PIDs of the processes accessing a file.

Answer 3

fuser will show you which processes are accessing a file or directory.