This is not supported/possible because Tomcat is running as a system service, not an interactively logged in user. Writing to the local disk isn't recommended/supported either in reality. You are supposed to store all data within the repositories. The repositories exist in SQL and are synchronized to the local disk for runtime use only. Anything on the disk gets overwritten by what exists in the repositories. The local disk is not backed up at all either.
Also be aware that CCX 8.0 will be a sealed Linux appliance. Your file system access will be extremely limited.