I can successfully start spring-boot with mvn spring-boot, the documentation mentions to gracefully exit the application hit ctrl-c.
Edit: in ubuntu, use the command:
fuser -k 8080/tcp
to kill the process. I'm using spring-boot 1.3.0-Build-snapshot and the problem still persist. My SO is Ubuntu and the problem occurs either running from Eclipse or from the console. The discussion about this issue is here. This seems to be an issue with spring-boot libraries, at least concerning tomcat libraries. I'm also in the line for the this fix. Unfortunately this is the price we pay for trying to use cutting edge technologies until they get matured.