use a helper script as recommended on https://docs.docker.com/articles/dockerfile_best-practices/#entrypoint
diff --git a/Dockerfile b/Dockerfile
index 10c6c0a..208d9e5 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -26,4 +26,5 @@
 
 USER jenkins
 
-ENTRYPOINT java $JAVA_OPTS -jar /usr/share/jenkins/jenkins.war --prefix=$JENKINS_PREFIX
+COPY jenkins.sh /usr/local/bin/jenkins.sh
+ENTRYPOINT ["/usr/local/bin/jenkins.sh"]