Selenium: Invalid “already running” error when starting server

Question

I am trying to get the Selenium server up and running. However, when I type:

java -jar selenium-server-standalone-2.0b3.jar

I get an Exception

Answer 1

If you started Selenium using Java (instead of via whatever testing framework you may or may not be using), you can kill all leftover Selenium instances with:

pkill java

That's guaranteed to kill any java relics (including selenium if started this way) - but be careful here - caveat is that you might be killing other procs too (due to the way pkill works). In my case, I want to kill anything running in the JVM, so this solved it for me.

As per the comment from Goldberg below, note that this will not kill any driver services or browsers running on your system!