My drives are very old, all pre-fail and I have a lot of residual files leftover from experiments early on with various dockers and plugins. I've backed up all the data I wish to preserve to a temporary NAS device. I've purchased the CMR drives and have begun the preclearing process ahead of resetting everything.

 

I'm not interested in preserving my existing dockers, plugins, VMs or drive configuration -- so what do I need to backup? What should I do with my existing boot drive in order to reuse it?

This is a little out-of-date but still might give you some ideas about what all those files on flash are for:

 

https://wiki.unraid.net/Upgrading_to_UnRAID_v6#Files_on_flash_drive

 

You really only need to concern yourself with the config folder.

 

Also, you can examine all of those files in a text editor except super.dat (the disk assignments).