The backup feature is disabled by default, enable via /etc/sysconfig/sceconfig. It creates a date stamped /sce/backup/ directory named after the extension and backs up the old SCE (*.sce, *.md5.txt, *.dep, *.lst) during re-import. Manually revert to original SCE if an update causes a non-functional boot or other breakage. For example, RC bug, broken Debian/Ubuntu package or corrupt file system. May also be used to revert to the original SCE if user wants to avoid specific Debian/Ubuntu software changes. As SCE breakage is rare, the backup system generally results in less manual tinkering within the /sce/ directory proper (ie. manually creating backups or saving old *.lst files).
No bells and whistles at this time, user responsible:
* Enable backup feature via sceconfig.
* Ensuring adequate drive freespace.
* Manually purge backup items as desired.
* Manually revert to backed up SCEs as needed.