Chosen Solution
I replaced my old HDD with an new 500 GB SSD and used Carbon Copy Cloner to put everything on my new SSD and then put it in my MacBook. It worked perfectly and I’ve been using my system with the new SSD for 2 months now. I want to now install the macOS Mojave Update on the SSD. It says it’s not the right GUID partition and it says I have to format my SSD again which I refuse to do. Can anyone help?
Depending on what OS-X you started out with on your old HDD over the years Apple has altered both the drive structure as well as the HFS+. As you cloned your drive Vs doing a proper OS install there maybe issues with it. I would download the OS you have cloned and create a OS installer so you can refresh it following this guide: How to create a bootable macOS Sierra installer drive you’ll find the other guides within this one if you are using a different OS. Now jumping to High Sierra and Mojave you will encounter a different issue as the OS installer see’s you have a GUID/HFS+ partition and wants to upgrade it to GUID/APFS which is the newer partition for SSD drives. As you have a SATA based SSD Vs PCI I don’t recommend jumping to the newer GUID/APFS as there are issues within High Sierra. Apple has updated the APFS within Mojave I personally haven’t made the effort to try it yet. Within High Sierra Installer you can alter the script so it won’t upgrade to APFS. Do keep in mind the installer also alters the systems firmware as well which you must do for Mojave to work. Here’s a guide someone has put together: Mojave MBR HFS Firmware Check Patch 10.14.x Do make sure you have a proper TimeMachine backup before attempting! I personally have not tried this yet.
