The only thing I did was replace jenkins.war with the new version. And then to start Jenkins I have a batch file which sets JENKINS_HOME. So it should be pointing to the same place it was before. Then the batch file starts Jenkins, like this:
SET JENKINS_HOME=%JENKINS_DISK_ROOT%\%JENKINS_WORKSPACE_FOLDER%\.jenkins
java -jar jenkins.war --httpPort=8081
sorry it’s not showing the slashes in that path, but in the script it’s correct