First, a disclaimer. This is not a normal article about personal finance, instead it is an article to share my hours of life-draining experience with others so they may avoid similar frustrations.
Rule #1: Before you upgrade your operating system do a time machine backup.
I did not follow Rule #1 and that is the source of all the problems. A week prior I had no trouble upgrading to Mojave on a MacBook and thought it wouldn’t be a problem for my Mac Mini. I considered taking the extra 20 minutes and backing up my files which they make so easy, but nah, I clicked upgrade.
Problems arise
The computer goes through its upgrading process and then boots and says “macOS could not be installed on your computer” and only gives me an option to restart. Clicking that just returns it to the same point, so it is stuck in a loop and there is no going back.
Holding option will allow you to select the startup disk. So I did that and I could boot perfectly into Bootcamp, but into the Mac partition would just go through the loop.
What about Disk Utility or Terminal?
If you are familiar with Macs you may know that you can boot them in Recovery Mode by holding command and R on startup which should provide you with some options such as restoring from Time Machine, Reinstalling macOS, getting online help, or going to Disk Utility.
In Disk Utility I could see my disks, but when I went to first aid it would fail. I could look at the imagine and navigate to my Photos, which was all I wanted, but I couldn’t move anything. So, then I figured maybe I could move things with Terminal. However, going that route failed with the error that it is a read-only file system.
Target Disk Mode
In the past days I learned that you can turn your Mac into an external hard drive by starting it in target disk mode. To do so hold T during start up. Then your screen should look like this.
Then you need to connect your Mac to another Mac via a thunderbolt cable, so if you don’t have an extra, borrow a friend’s or go to a nice library. Once the two Macs are connected you can drag files to and from the target disk. At first only the Bootcamp drive was visible, but after a minute the main hard drive was recognized. At that point I dragged the files I wanted off the disk. What is your computer but a bunch of files anyway?
Restoring
Instead of paying Apple for a bigger hard drive I upgraded my hard drive the frugal way. Since I duplicated the hard drive in Disk Utility I clicked Restore and selected my old hard drive which I saved just in case. Another way would be to use your latest Time Machine Backup. And the final way would be to reinstall macOS and then transfer all your files.
Conclusion
I ended up successfully installing Mojave the next time around and am still transferring my 220GB Photos library now. I definitely learned my lesson to always back up before doing an upgrade or otherwise. In fact, after I load photos I will update my Time Machine. I really hope you were able to get what you needed. And hey, if you want to save some money maybe check out my other articles.