How to kill the existing rt?

I can’t open the RT instance, the system show below error, then my question is how to kill the existing RT?

You’re probably already running a web server (Apache, nginx, etc) on port 80, so the standalone RT server can’t use that port. If its another stand alone rt-server instance you could kill it using killall -9 rt-server.

Otherwise you’ll either need to configure your existing web server to run the RT code (using something like FCGI) or more shutdown the existing web server (if its not in use) or, if you’re just testing RT, run the rt-server on a different port (say 8000) using the command rt-server --port 8000 and then using :8000 in the URLs you use to talk to RT.

Thank you very much , the command works now.