External HD wont hold as start up disk

[Not Julias Brother]

I have a late 2013 iMac that I have cloned onto a Hitachi SSD external HD using Carbon Copy. I made this drive bootable, but the only way I can boot it is using the option key and start up manager. When I try to change the start up disk in System Preferences, it says the external HD is going to be the start up disk but on restart, the internal drive is the one that loads. I have updated PRAM.

Any ideas?

 

[TonyAguila]

I have a late 2013 iMac that I have cloned onto a Hitachi SSD external HD using Carbon Copy. I made this drive bootable, but the only way I can boot it is using the option key and start up manager. When I try to change the start up disk in System Preferences, it says the external HD is going to be the start up disk but on restart, the internal drive is the one that loads. I have updated PRAM.

Any ideas?

What version of macOS do you have installed? I’m among the #1 fans of CCC, but not for cloning bootable drives. Even when they made it capable of creating bootable clones, I stayed with copying just the data part of the drive and creating a fresh install of macOS and afterwards migrating data from the clone.

Have you tried selecting the startup drive from System Settings? If you cannot select the external as your boot drive from System Settings, then the Mac is probably not recognizing it as a bootable device. I also let everyone know that after zapping PRAM and you have SSDs in your setup, you need to enable TRIM afterwards, built-in or external.

 

[Not Julias Brother]

I’m running Mojave. I can select the drive from system settings but when I restart it goes back to the internal drive.
A weird anomaly, when I start in Safe Mode, it starts with the external drive.
Ideas?

 

[TonyAguila]

I’m running Mojave. I can select the drive from system settings but when I restart it goes back to the internal drive.
A weird anomaly, when I start in Safe Mode, it starts with the external drive.
Ideas?

I’m assuming your internal drive is an HD or Fusion drive. If you have changed it to an SSD, it shouldn’t be much difference. The first thing I would do is reinstall Mojave on top of the present system. Do you have the newest version (10.14.6)? If not, you should download it and reinstall it from Safe Mode. That should at least make sure that your system files are fresh and undamaged.

If you do not have the latest version of Mojave, you can download it from the App Store or using Terminal. I’m also assuming that you have a Time Machine backup, or a non-bootable CCC clone. You don’t want a bootable CCC clone to avoid reloading any damaged file from your previous system. I used to keep copies of the latest system installer and/or combo updater. I routinely reinstall macOS at the first sign of odd behavior. I also maintain a second user (admin) account, barebones, from where I could do the installation.

And let me reiterate, you must re-enable TRIM every time you do a PRAM reset.