Delete old Time Machine back ups and keep only newest one for computer I no longer have

pgugger wrote:

Thanks for your suggestion. Do you think I could copy the whole Backups.backupdb to another external drive and then delete from this particular external drive without much risk? In general I have never tried moving or copying the back up folder from one drive to another...

It looks like you are on Monterey. Have a look at this link, noting that there are separate drop down menus with different instructions for Catalina, Big Sur, Monterey.

https://support.apple.com/guide/mac-help/if-the-time-machine-backup-disk-is-full-mh15137/10.15/mac/10.15

Look at instructions for each operating system. Each says

"If you do run out of space, it’s best to connect a new backup disk. After you connect the new disk, open Time Machine preferences, then select it as your Time Machine backup disk."

But for Catalina, it also says "If you connect a larger disk and wish to preserve your existing backup history, you can copy the Backups.backupdb folder from the old disk to the new one. Use Finder, and not Terminal or any other app, to copy the Backups.backupdb folder. (The folder is large, and it may take a long time to copy.)"

Looking online, one can find many accounts of people trying to do this and some not succeeding, primarily due to the size and complexity of the Backups.backupdb folder, the process can take days.

But notably, for Big Sur and Monterey this additional instruction is not there in Apple's support article. In other words, Apple does not recommend trying to copy the existing Time Machine backup from the original drive to a new one, for Big Sur and Monterey. Not sure why, but note that APFS (not HFS+) is used for Time Machine backups starting with Big Sur and the backup process and file architecture changed starting with Big Sur.

So I think the safer approach is to keep the old backup drive as is.

Here is what I suggest to preserve this backup of a computer you no longer have access to. Obtain a fresh new external drive. Install a bootable MacOS on that external drive, must be the same or newer versus what is on your Time Machine backup that you are concerned about. On that external bootable drive, create only one new administrator user, say ADMIN. Then boot into that external drive and run Migration Assistant to migrate everything from that older Time Machine backup you want to preserve to that new external drive, user accounts and files. Now you have everything from your old Mac but in native Mac file format. You can then make "clones" of that new external drive (using Carbon Copy Cloner, SuperDuper, or other utilities) so you have multiple copies and the files are easily accessible with the finder.

Unless you do something like this, you are trusting (hoping) that your one and only Time Machine backup of that old computer will last forever, which it will not. Someday it will stop working.

You can certainly TRY to copy the Time Machine backup to another drive, but I would not delete anything from the original Time Machine backup until you have carefully verified that the copy worked and all the backed up files are accessible.

IMHO - keep the drive intact and put it aside.

Start with a New Dedicated Drive for the machine .

Mucking around on the existing TM Drive increases the Risk of corrupting the index files used to maintain the backups intact and usable.

Have never attempted, so take any advised offered and pause long enough for More Learned Contributors to join into your question. That is what is suggested before moving forwards with below.

https://appletoolbox.com/transfer-your-time-machine-backups-to-a-new-drive-with-this-guide/

https://www.howtogeek.com/335090/how-to-migrate-a-time-machine-backup-to-another-drive/

Very much agree with @Steve626 on not risking damaging the existing TM Backup Drive bu=y attempting to move it over to a larger drive.

Start fresh with a new dedicated drive IMHO would server the computer and you better.

So one should just keep buying disks like money grows on trees, and if one wants to find a file from a couple years ago, it should only take half a day or so to search all your old time machine disks to locate it. I think Time Machine needs a major redesign.

Thanks for the update and best in the future.

Do come back to ASC Forums if or when additional questions may arise.