Upgrading from SonarQube 5.6.4 LTS to SonarQube 6.7.4 LTS using the upgrade instructions provided (https://docs.sonarqube.org/display/SONAR/Upgrading) causes all projects to disappear and all configured rules in quality profiles to be deactivated.
A solution is posted on StackOverflow (link) to delete the
temp directories before the DB migration process. This fixed the issue for me.
Is this the correct way to solve this problem? If so, can the upgrade documentation be amended to include this step? This would have saved myself and others a fair amount of trouble.