Can't boot from backup

[idntknw]

I can't seem to boot from a external cloned backup. I chose it from system preferences to boot to it but it just boots into the main drive. I tried to use option during startup and the external drive isn't listed.

Any ideas?

 

[Fishrrman]

My guess is that there's something peculiar about the clone that makes it unbootable.

Sometimes this has to do with the underlying formatting of the target drive.

Is your internal (source) drive still usable?
What did you use to create the clone? (CCC or SD?)

Have you tried "updating the cloned backup"?

Hmmm... since this is being posted in the High Sierra forum:
- what is the formatting of your internal drive (HFS+ or APFS?)?
- what is the formatting scheme used on the cloned backup?

 

[idntknw]

Thanks for the reply. Yes the drive is still useable. I did use CCC to clone high sierra to the external drive. I partitioned it with APFS format and the internal is APFS.

My current setup is I partitioned my internal drive to test high sierra. I used CCC to clone high sierra to the external drive and was trying to boot into it so I could erase the main drive then clone high sierra to it.

Edit: I erased the external drive and did another backup using CCC and I’m now able to boot from the external drive.

There shouldn’t be any problem erasing the main drive then cloning over the external to it now should it? When I erase the main drive does it matter what format?