How can I transfer Time Machine backups to a new drive without losing access on MacBook Air?

Ok, I think the issue here is with Time Machine snapshots. By that I mean, even using the Disk Utility, making a clone of an existing TM backup drive is just not that simple, but I thought it may be worth a try. At least, you validated that process is still not available with the newer versions of macOS.

Ref: https://eclecticlight.co/2022/07/19/what-can-you-do-with-time-machine-backups-on-apfs/

That leads us to only one other option that I am aware of, and that is ASR (Apple Software Restore) ... but, AFAIK, it is designed to make bootable clones of your Mac's internal drive. I am not aware that it could be used for cloning an external drive to another one.

Ref: How To Clone Your Mac Using ASR - Apple Community

.... so, what does all that mean? Chances are you are not going to be able to clone your existing backup to a new drive. There are third-party apps, like Carbon Copy Cloner, that might be able to make a clone copy, but whether or not, it will work for TM is another matter. Your best move going forward is to retain your old drive as an archive, and then, start a new TM backup on your new drive. Of course, you will still need to get another drive for basic file storage.

Tesserax wrote:

Ok, I think the issue here is with Time Machine snapshots. By that I mean, even using the Disk Utility, making a clone of an existing TM backup drive is just not that simple, but I thought it may be worth a try. At least, you validated that process is still not available with the newer versions of macOS.

Ref: https://eclecticlight.co/2022/07/19/what-can-you-do-with-time-machine-backups-on-apfs/

That leads us to only one other option that I am aware of, and that is ASR (Apple Software Restore) ... but, AFAIK, it is designed to make bootable clones of your Mac's internal drive. I am not aware that it could be used for cloning an external drive to another one.

Ref: How To Clone Your Mac Using ASR - Apple Community

.... so, what does all that mean? Chances are you are not going to be able to clone your existing backup to a new drive. There are third-party apps, like Carbon Copy Cloner, that might be able to make a clone copy, but whether or not, it will work for TM is another matter. Your best move going forward is to retain your old drive as an archive, and then, start a new TM backup on your new drive. Of course, you will still need to get another drive for basic file storage.

Two cents and addition info regarding CCC Cloning a TM Backup Drive

https://support.bombich.com/hc/en-us/articles/20686476880791-Can-I-use-CCC-to-copy-a-Time-Machine-backup

CCC specifically disallows copying anything to or from a Time Machine backup volume

Unfortunately, Apple has made this pretty much impossible with their newest versions of macOS. The simple process of copying (or cloning) the drive to another one is not recommended as it typically results in a "broken" Time Machine backup set.

However, it can be attempted if those backups are critical to you ...

... and the following are the basic steps to do so. Again, I can't guarantee the results, so proceed at your own risk.

Step 1: Verify that your new drive has ample storage space for the current backup set. Overall, the drive's size should be 2-3x the total internal drive space of your Mac. Note: If you haven't purchased the new drive yet, I suggest that you consider getting a HDD over an SSD for this purpose for three reasons: 1) There is no real performance gain using a SSD for backups, 2) The effect of writing numerous files to a SSD will "wear" out its memory cells quickly rendering them unusable, and 3) HDDs are still far cheaper per GB than SSDs.

Step 2: Make an Exact (Clone) Copy of the Source Backup Drive.

1. Do not use the Finder app to just copy the TM backup to the new drive. Instead you will two options to "clone" the backup to the new drive: 1) The Disk Utility, or 2) Via the Terminal app. Using the Disk Utility if far simpler, so let's go with that route.
2. Open Disk Utility. It is located at: /Applications/Utilities.
3. Select the New Drive in the left sidebar.
4. Click the Erase button first, choose the correct format (APFS), and make sure the Scheme is set to: GUID Partition Map.
5. Name the new drive something appropriate like NewTM.
6. With the new drive selected, click Restore in the toolbar.
7. For "Restore from:", choose your old Time Machine drive. Disk Utility will copy everything from the old to the new disk, byte for byte.
8. Once done, unplug the old drive, plug in the new one.

Step 3: Add the new drive to Time Machine

1. Go to System Settings > Time Machine
2. Add the new drive if needed. macOS may automatically recognize the backup; if not, we will need to use the tmutil inheritbackup command in the Terminal.

That command would be: sudo tmutil inheritbackup /Volumes/NewTM/Backups.backupdb/YourMacName

Step 4: Test It!

Run a new Time Machine backup with the newly cloned drive and try restoring a file using the Time Machine interface to make sure history is preserved.

When Disk Utility doesn’t explicitly offer the GUID Partition Map option, it's usually because you’re formatting a volume rather than the entire physical disk. Restores, especially those involving system volumes or bootable clones, typically require the destination to be a whole disk formatted with GUID, not just a single APFS container.

To resolve this:

1. Open Disk Utility, then go to the View menu and choose Show All Devices. This is key — it reveals the actual physical disks, not just their containers or volumes.
2. Select the physical drive (not the volume or container) for your new drive — it’ll be the topmost item under the drive’s name (like "Apple SSD Media" or the brand name of your external).
3. Click Erase, and in the erase dialog: Choose APFS as the format.
4. Choose GUID Partition Map as the scheme (this option will now appear if you selected the physical disk).
5. Name the disk as desired, then erase.
6. Once formatted, try the restore operation again. This time it should validate the source and proceed without throwing OSStatus error 49245.

How to transfer Time Machine backups - Apple Community

+1

Thanks for verifying that CCC will not work in this case.

Tesserax wrote:

+1

Thanks for verifying that CCC will not work in this case.

+1 , Pleasure to work with you