Ext. Mac OS Drive clone won't boot...

[Jodeo]

I've cloned my internal drive to one of the two partitions of an external drive. Honestly, I can't recall for sure if I was able to boot from that external drive.

I've since done a clean install of Mac OS 10. 11 (El Capitan) on the second external partition. Then, I used Migration Asst. to update the 2nd partition. This is to serve as staging for upgrading an iMac (now 11 years old) AND to have a back-up of Yosemite should the El Cap not be as good (I've read that older iMacs actually perform a bit better with it).

When I do try to boot from the external 10.10 external partition, I get the 'do not enter' aka 'ghost buster' icon.

I am able to boot fine from the El Cap 10.11 external partition just fine. (Also, the internal Yosemite drive boots fine too.)

So.
Do I need to re-clone my internal drive to ext. partition 1? Or just run the 10.10.5 Combo Update? Or... something else (short of buying a new Mac)?


Thanks!

 

[DeltaMac]

The combo updater would require you to reboot that Yosemite partition. If it is already not booting, the combo updater won't fix that.
If you have a bootable Yosemite installer, maybe on a flash drive, you can boot to that, and reinstall the system on your external partition. You should expect that will fix it.

 

[Riwam]

I've cloned my internal drive to one of the two partitions of an external drive. Honestly, I can't recall for sure if I was able to boot from that external drive.

I've since done a clean install of Mac OS 10. 11 (El Capitan) on the second external partition. Then, I used Migration Asst. to update the 2nd partition. This is to serve as staging for upgrading an iMac (now 11 years old) AND to have a back-up of Yosemite should the El Cap not be as good (I've read that older iMacs actually perform a bit better with it).

When I do try to boot from the external 10.10 external partition, I get the 'do not enter' aka 'ghost buster' icon.

I am able to boot fine from the El Cap 10.11 external partition just fine. (Also, the internal Yosemite drive boots fine too.)

So.
Do I need to re-clone my internal drive to ext. partition 1? Or just run the 10.10.5 Combo Update? Or... something else (short of buying a new Mac)?


Thanks!

I am not sure if it might help you but I have had good experiences with DiskWarrior. It must be run from a different volume to the faulty one.
It helped me on many occasions avoiding me to have to reinstall a MacOS which did not boot.
Ed