Continue with the same Time Machine External HD backup with fresh OS X install problem

Question

Level 1

10 points

Continue with the same Time Machine External HD backup with fresh OS X install problem

Hi all, I am looking for a solution to having using the same Time Machine back up drive and continuity with files backing up after a fresh OS X high Sierra install on my MacBook Pro 13". I have been using a 2tb hd for time machine back up with the same OS X high Sierra for 2 years and decided a fresh install instead of restoring from Time Machine due to software installation licensing issues. I made my user name and MacBook Pro hd name the same as previously setup. However upon trying to have a continuity in backing up to my Time Machine HD it wants to treat it as entirely new back up which means taking up a large HD space. Part of the project files are already in the Time Machine and I don't want to have a fresh duplicate back up. This might mean getting a new HD to do another fresh time machine back up which I am trying to avoid. Is there a way to make Time Machine recognise existing back up and perform with continuity like before? Hope this makes sense. Thank-you!

Posted on Jan 23, 2025 7:16 PM

Reply

Answer 1

ursinus Author

Level 1

10 points

Jan 25, 2025 12:46 AM in response to christopher rigby1

Hi Christopher, thanks so much for replying and sharing your tips. I will keep that in mind in terms of deleting repeated files in the back up and it is time consuming! I have found a way after much frustrating trial and error. The term is called inherit the existing TM back up drive. Here's are two websites that explains using unix script to override and make the refreshed system to link up with existing back ups so not to have back up from scratch again! I wasn't prepared to go and buy another hard drive to start a fresh backup.

https://acecilia.medium.com/mac-and-time-machine-inherit-a-backup-from-another-computer-dbad4d8aad79

https://simon.heimlicher.com/technology/time-machine-inherit-backup-using-tmutil/

I think I will not only use TM back up from here on to save future troubles. I will use other back up systems to complement.

Reply

Answer 2

Jan 24, 2025 8:53 AM in response to ursinus

If I've understood correctly, you've created a fresh install of High Sierra over what was there previously. EVEN IF you could have the 'continuity' you want, the next backup would still be horrendously large, as your system - including users - would be seen as new by TM even though your actual user files are the same.

Your best bet - unless someone else knows different - would be to go ahead with the new TM, but then go into the previous TM backup via the app and delete all instances of large files you know you don't need to keep; this would be rather time-consuming but could potentially free up a large amount of drive space. .

Reply

Continue with the same Time Machine External HD backup with fresh OS X install problem

Similar questions