The Grails tutorial I read said provided instructions for changing the default server port from 8080 to some other value, so that you would not need to specify an alternate server port every time you run-app. It said that you should open $GRAILS_HOME/scripts/Init.groovy and look for a line setting the value of serverPort.
The problem is that this tutorial was written in 2008, and while you wouldn’t think that much would have changed since then, apparently the Grails config files have been refactored. Init.groovy now appears to be a much higher-level file, and serverPort isn’t specified in it.
After searching the Grails directory, I found out that the new file to edit is $GRAILS_HOME/scripts/_GrailsSettings.groovy. Open it and look for the following line:
serverPort = getPropertyValue("server.port", 8080).toInteger()
I believe the getPropertyValue method checks properties sent in via the command line or configured in some other way. If it’s not set, though, it uses the second parameter as the default value. Change it from 8080 to some other port, like 9090, and the next time you run-app you’ll be running on the new port instead