Rails: A server is already running.

Sometimes, when you run rails server or rails s , it ends up with this error

A server is already running.

This is because you’ve left a server in suspended status. The shortest solution is to kill this process starting the server again. Run these commands to do this

To kill the process (suspended server)

sudo kill -9 $(lsof -i :3000 -t)

Then run the server with

rails s