Presently, the init script template cd's into a working directory when running the init script (reference: https://github.com/apache/bigtop/blob/master/bigtop-packages/src/templates/init.d.tmpl#L86)
When no such variable (WORKING_DIR) is provided when building the init script, it will default to the user in question's home directory.
This can lead to problems in upgrade scenarios. Say the user "mapred" already exists (say because the user had an old or existing installation of Bigtop) and that user has a different working directory for the user that no longer exists.
When Bigtop package installation occurs, it doesn't create the user if it already exists. In such a case, the init script fails because it can't cd into the home directory.