Back up /Users folder

[bsk]

I have two identical disks & I want one the target to be a bootable version of the source.

I want to be able to do:

1) one-off backups my current stable OS X installation to the target disk. This is my current stable OS X installation & that will remain until after I'm happy with whatever OS X update I've installed. This seems to be no problem with SuperDuper.

2) update just the User folder on the target disk - this ensures all my current data is backed up so that in emergencies I can reboot in the target disk with my last working OS but with my dats being at least reasonably current.

This I last thing cannot figure. The script keeps on on overwriting System files. I cannot seem to get it to just change the Users folders and ignore the rest.

Thanks for any advice.