I tried to remove a file in Linux using rm -rf file_name, but got the error:
rm: file_name not removed. Text file busy
How ca
@jim's answer is correct -- fuser is what you want.
Additionally (or alternately), you can use lsof to get more information including the username, in case you need permission (without having to run an additional command) to kill the process. (THough of course, if killing the process is what you want, fuser can do that with its -k option. You can have fuser use other signals with the -s option -- check the man page for details.)
For example, with a tail -F /etc/passwd running in one window:
ghoti@pc:~$ lsof | grep passwd
tail 12470 ghoti 3r REG 251,0 2037 51515911 /etc/passwd
Note that you can also use lsof to find out what processes are using particular sockets. An excellent tool to have in your arsenal.