Problem scenario
You are using SonarQube Community Edition. SonarQube will not start. You recently moved a .jar file into a plugins directory. You want to use this plugin to analyze code.
The SonarQube logs may register something like "Background initialization failed. Stopping SonarQube java.lang.IllegalStateException: Fail to load plugin C / C++ / Objective-C [cpp]"
The logs may also say something like this: "Unable to register extension com.A.A.A.B.F from plugin 'cpp' or "NoClassFoundError...PropertiesDao".
What should you do to get SonarQube to start?
Solution
Stop SonarQube services. Remove the recently added plugin (e.g., move the .jar file from a plugin directory). Restart SonarQube services.
You cannot use the C / C++ plugin without a paid version of SonarQube such as the Developer Edition.