The next big macOS Mojave will be out on Monday. There are all kinds of articles on the web about preparing your machine for the upgrade which include backups. I have several backups of my iMac including a clone and backups of my Pictures and Home Folder to external drives. I also recently started using BackBlaze offsite backup so I think I am covered. But, what if you do not use Time Machine or some other type of backup. Then, you might wish to make a “Local Snapshot” of your current system before installing Mojave. There is a way to do that without Time Machine.
Time Machine backups are created in the form of Snapshots. It creates and deletes them as it backs up all during the day. However, if you do not use Time Machine, you can make a Local Snapshot without it. Why would you wish to do that? Well, if your Mojave install goes bad or just is not what you expected you can, theoretically, restore a Local Snapshot to your Mac in place of Mojave. Here is how to do that.
First, open the Terminal App (Utilities Folder) and type in tmutil snapshot:
When you hit Return ⮐ the Terminal App makes a Local Snapshot of your current install. It stores that Snapshot where Time Machine keeps that Snapshot, don’t ask me where that is, I don’t know. This Snapshot creation process takes a few minutes. When it is finished you should see a window like this:
So, lets say you install Mojave, but decide to roll back your system. The first thing you need to do is Restart your Mac holding down the Command ⌘ key and the letter “R” right after you hear the startup chime. This is Restarting into Recovery mode. Keep holding that key combination down until you see this window:
Because you are going to use a Snapshot to Restore your system you want to use the Time Machine setting. Now, click Continue to get to this next screen:
I am very sorry about the image quality here, but had to get these images in Recovery mode using my iPhone. From this screen click Continue and select the drive where the Snapshot is to stored, your main boot drive:
When you click Continue you will be taken to a screen listing any Snapshots you have:
You would then select the appropriate Snapshot and click Continue, your Mac would be Restored to the 10.13.6 OS. If you were using a Time Machine backup you would essentially go through this same process. I did not really Restore from this point, but everything I have read says you are good to go here. All you have to do is wait for this to finish and Reboot into your previous OS.
As far as I can tell from using the Mojave Beta, it is a pretty stable OS. However, if you use a ton of software like me, there are bound to be a few little issues. If I install Mojave and then change my mind I will Restore High Sierra using my Clone. However, if you do not have a clone, then this Snapshot method may suffice.