I was in the process of restoring my Mac Mini 2018 running macOS Catalina 10.15.1 to an earlier Time Machine backup encapsulating the latest version of macOS Mojave via macOS Recovery, when the process failed. I got the message:
An error occurred while restoring from the backup. Try restoring from a different backup or reinstall macOS and then transfer your information from a Time Machine backup using Migration assistant.
I then restarted the Mac, and tried to enter macOS Recovery (⌘+R on boot). I saw the "spinning globe" icon for about 4 minutes, but then it gave the error:
I have since reset the NVRAM (⌥+⌘+P+R) but I continually get the "-1008F" error when trying to access macOS Recovery. However, in this Reddit thread regarding this nominal issue for the macOS Catalina Beta, they suggest to try another Recovery key combination (⌘+⌥+R on boot), and this indeed gets me into some sort of Recovery mode where I'm first asked to enter my Apple ID, and I can afterwards see the usual Recovery options like Disk Utility, Reinstall MacOS, Restore from Time Machine backup, etc.
However, I am unsure on how to proceed from this point. As mentioned, my previous Time Machine restoration failed from macOS Recovery (the backup is located on a Synology NAS on my network; I have an additional concurrent backup on another Synology NAS which I haven't tried yet).
Furthermore, according to some sources I found on the net when searching for the "-1008F" error, it can be indicative of hardware failure and some people seem to have had hardware parts replaced. I did notice that when I entered macOS Recovery the first time, it was lingering a very long time on the state: "Examining available disks...".
When checking Disk Utility, I have two Mac HD Partitions apparently since installing macOS Catalina:
Macintosh HD for the OS partition and
Macintosh HD - Data for user data. Since macOS Mojave doesn't use this setup, do I need to "merge" these partitions to successfully restore from the Time Machine backup or reinstall macOS Mojave from scratch? I wonder this because when I navigate to the Time Machine backup process, it asks me which partition to restore into – and I can select both the
Macintosh HD and
Macintosh HD - Data partitions. This doesn't feel right, as macOS Mojave uses one partition for both OS and user data.
If I indeed need to "merge" the two partitions (e.g. by reformatting them into one "Macintosh HD" partition), how do I do that? A user in this Reddit thread regarding the MacOS Catalina beta suggests to "Erase the APFS container and format it again as APFS", but I don't understand what the user means by the "AFPS container". I don't see a single container encapsulating both partitions, rather they appear like two separate things seen in the images below:
To make a long story short: how do I best resolve this problem and restore my Time Machine backup to my macOS Mojave system from the now broken macOS Catalina system?
Do I need to reformat the drive first, and can I then restore from my Time Machine backup – or should I install a fresh copy of macOS Mojave and then attempt restoration via the Migration Assistant?