Server starts 3 Java processes instead of one

Before 4.5, starting SonarQube server used to launch only the Web server. Starting with 4.5, the search index has been pulled out of the web server. Therefore, starting SonarQube creates 3 processes feeding 1 log file (sonar.log):

In order to communicate with each other, port 9001 needs to be opened for communication with Search server.

For servers with more than one IP address, it is possible to specify which one will be used for listening on the specified port.

Java 6 Support

JRE / JDK 6 is no longer supported to run SonarQube starting from 4.5.1

Some files in the installation folder have changed

Because of the previous point:

"sonar.profile" no more considered in sub projects

For a long time, it's been possible to associate a project with some quality profile in the UI only at project level - but not at sub project level. On batch side, it was possible - thanks to a side effect - to set different values of "sonar.profile" for each sub project of a multi-module project. This corner case is no more supported.

Technical Debt plugin must be removed

The deprecated Technical Debt Plugin conflicts with this version of SonarQube and must be uninstalled before the upgrade.

Security Rules plugin must be removed

The deprecated Security Rules Plugin uses APIs deprecated since SonarQube 2.7 and that were removed in 4.5.1. Therefore, it must be uninstalled before the upgrade.