Near Disaster Reverting to HFS+

[perquesta]

I have the latest 27" iMac.
After a recent High Sierra beta formatted my Boot Fusion Drive to APFS, I attempted to revert the drive back to HFS+ in preparation for the release of High Sierra on the 25th. I used the routine outlined on the Apple Beta Software Program page.

However, when I attempted to use step 8 (erase the boot disk using Disk Utility) the boot disk was rendered unavailable and I was subsequently not able to format it as either APFS or HFS+. Nothing I tried would work.

Fortunately I had a backup on an external hard drive created by Carbon Copy Cloner. I was able to boot back into High Sierra using that disk. However, I am now having a little trouble restoring the iMac hard drive using Carbon Copy Cloner.

 

[tn-xyz]

it should be resolved by following the terminal commands as stated on the same page. give it a try.

 

[perquesta]

Thanks tn-xyz. I was using the first method, using an external drive. I did use the terminal commands to create a bootable installer on a 16Gb USB stick, but it led to the problems I described earlier.

However, I am now pleased to announce that I was able to reinstate my hard drive using Carbon Copy Cloner, leaving me with beta 17A360a on a HFS+ system hard drive (1.03 TB Fusion Drive). Now I will wait till Monday to install the High Sierra release.

 

[Fishrrman]

Your experience provides a good example of why a bootable cloned backup trumps a Time Machine backup nearly all the time.

What would you have done without the CCC clone?

 

[robeddie]

Your experience provides a good example of why a bootable cloned backup trumps a Time Machine backup nearly all the time.

What would you have done without the CCC clone?

Agreed! CCC (or similar programs) that can make an exact, bootable clone have gotten me out of a pinch countless times over the years.

 

[perquesta]

Your experience provides a good example of why a bootable cloned backup trumps a Time Machine backup nearly all the time.

What would you have done without the CCC clone?

I've no idea. The software on the USB installer was no hope. I would have had no way of contacting the community for ideas. I was thinking of using Safari on my iPhone to search for possible solutions. I agree that CCC is a godsend. I was using a trial version, but promptly bought it afterwards.