anchor.diff:  ENV JENKINS_HOME /var/jenkins_home
   ENV JENKINS_SLAVE_AGENT_PORT 50000
   
  +ARG user=jenkins
  +ARG group=jenkins
  +ARG uid=1000
  +ARG gid=1000
  +
   # Jenkins is run with user `jenkins`, uid = 1000
   # If you bind mount a volume from the host or a data container, 
   # ensure you use the same uid
  -RUN useradd -d "$JENKINS_HOME" -u 1000 -m -s /bin/bash jenkins
  +RUN groupadd -g ${gid} ${group} \
  +    && useradd -d "$JENKINS_HOME" -u ${uid} -g ${gid} -m -s /bin/bash ${user}
   
   # Jenkins home directory is a volume, so configuration and build history 
   # can be persisted and survive image upgrades
  
positive.code: 
  ENV COPY_REFERENCE_FILE_LOG $JENKINS_HOME/copy_reference_file.log
  
  USER jenkins
  
  COPY jenkins.sh /usr/local/bin/jenkins.sh
  ENTRYPOINT ["/bin/tini", "--", "/usr/local/bin/jenkins.sh"]
  
negative.code:   && echo "$JENKINS_SHA /usr/share/jenkins/jenkins.war" | sha1sum -c -
  
  ENV JENKINS_UC https://updates.jenkins-ci.org
  RUN chown -R ${user} "$JENKINS_HOME" /usr/share/jenkins/ref
  
  # for main web interface:
  EXPOSE 8080
  