A clone of your Mac is essentially a backup of all the data you can make bootable, so when you connect the disk to another Mac, you just reboot and carry on from where you left off.
Cloning your Mac’s main drive is a great way to protect yourself against potential problems when, for example, you might be installing a new version of macOS — especially if it’s still in beta. But clones can also be of use during travel or business trips, if you’re worried that your Mac might get lost, stolen or damaged.
If you need to recover files from a failing system, you can clone the whole drive and then recover files from the clone, removing the possibility that the drive will fail completely before your files are recovered.
A clone backup differs from the now popular incremental backup in that it creates a snapshot of your Mac that is preserved for as long as you want it, whereas incremental backups update themselves at regular intervals.
There are a few things you need in order to clone your Mac and use it as a backup. First, you need an external hard drive or SSD with a volume that’s clean and empty, which means it should either be brand new or completely erased beforehand.
Next, you’ll need software to create the clone. There are several applications that are available for Macs that you can use. We recommend going with Disk Drill. Disk Drill can help you recover data from a failed drive and allows you to create byte-for-byte copies of a disk and save them as a disk image. In other words — clone your Mac.
Finally, you need a safe place to store your clone — a backup is no good if you can’t find it when you need it.
If you have a regular backup routine, it’s a good idea to run one before you start the process of cloning your Mac. It sounds daft to run a backup just before you create a backup, but it’s always better to be safe than sorry.
If you’re using a disk that’s been used before, you’ll need to erase it completely to make it ready for the clone. We’ll assume you’re going to use the whole disk as a single volume.
Plug the external hard drive into your Mac, and launch Disk Utility. Go to the Utilities folder in Applications and double-click on Disk Utility to open it.
Erase the drive. Click on the external drive in the sidebar and then the Erase tab. In most cases, the format will automatically be set to macOS Extended and the scheme to GUID Partition Map. You can leave it at that. If you’re running macOS High Sierra and will only use the drive with a Mac using High Sierra, you can choose APFS from the Format menu. Give your drive a name and click Erase.
Then open Setapp desktop app and launch Disk Drill. If you haven’t already installed Disk Drill, get Setapp account and install the app.
Disk Drill will now create an exact copy of your boot drive as a disk image, saved on the external drive.
Once the disk image has been created, you can double-click on it to mount it in the Finder. It will then be treated like any other volume by macOS and you can drag and drop files from it to your main drive. That’s fine if you only lose a few files and folders and need to recover them, but what if your boot drive fails or you need to recover the whole disk from the image?
You can’t boot a Mac from a disk image, but you can restore the clone to your Mac’s boot drive if you need to. Here’s how.
1. Shut down your Mac
2. Restart in recovery mode. Restart your Mac while holding down the Command and “R” keys.
3. Erase your boot drive. Click on Disk Utilities in the Utilities application and then Erase. If the disk image you’re restoring from has macOS High Sierra installed, choose APFS from the format menu, otherwise, choose macOS Extended (Journaled). Give it a name and click Erase.
4. Restore the disk image. Still in Disk Utility, click on the drive you just erased. Now go to the File menu and choose Restore. Click the Image button and navigate to the disk image you created in Disk Drill. Then Restore.
Alternatively, if you know beforehand that you’re going to need to boot from the clone, choose Create Boot Drive and then Boot Drive for data recovery instead of Backup when you've created the disk image of your drive.
If you don’t need to completely replace your Mac’s startup disk, but need to recover files from a disk image — perhaps because you created the image from a failing drive that has now failed completely — you also can do that in Disk Drill.
1. Mount the drive. Double-click on the disk image in the Finder to mount it.
2. Recover data in Disk Drill. Select the mounted volume in Disk Drill’s main window and click Recover. Follow the on-screen instructions to scan the volume, identify and recover the files you need. Remember that you should never recover files to a failing hard drive, so choose a destination that you know is stable.
You now know how to clone your Mac so you can use it as a backup for files and folders, as well as to recover files and, if you need to, boot from the clone and restore the image to your Mac’s startup disk. Let’s hope you never need it, but, if the tragedy comes around, at least you are prepared.