Thanks everyone, great posts/ and info.
Ok, I'm leaning to in emergency: use DU, then go online from the clone drive to : Tech Tool, Drive Genius,DW ... (in that order, cheapest to most expensive), and if none on those work:
Erase, and install the current OS, then use migration assistant.
Artie says having the pure OS is the way to go.
My SD backups, have been bootable and working ok, I'm open to CCC, but from info here and what I just outlined (thanks H for info), could stay with SD fine.
Question H: I do have install El Capitan in my apps folder on my desktop. I'm not sure why it's there. I did the download the other day and got a bit scared and quit when it said, "you already have installed", maybe it downloaded anyway? Or was there somehow otherwise.
Today, I did the download ElCapitan, to laptop, but nothing downloaded. Am I doing something wrong? I saw translucent wheel spinning in the upper left of App store window, but no progress bar and no download upon completion. How does this work exactly? progress bar, how long take, And does it matter later that your downloaded version may not be the most up to date later? I suppose you can the just update the OS at that point?
(also, I could just copy the Install El Capitan in my desktop app folder to the app folder of the laptop..?) Thanks.
