Time Machine setup on new iMac with existing backup

Question

Level 1

4 points

Time Machine setup on new iMac with existing backup

I’d really appreciate any help: I’ve just set up a new iMac and migrated all my data from my old one. I’d like to continue using my existing Time Machine backup drive with the new machine.

What’s the correct way to connect and configure the drive for future backups?
Do I need to adjust any settings in macOS (Tahoe) to ensure it’s recognized?
Can I keep my old backups and add new ones from the new iMac?
Are there pitfalls I should watch out for (permissions, formatting, duplicate backups, data loss)?

I would greatly appreciate any guidance or tips.

Posted on Dec 14, 2025 5:24 AM

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Answer 1

dialabrain

Level 10

135,761 points

Dec 14, 2025 6:57 AM in response to Thomoos

Basically, if you want to use the existing drive for Time Machine, it will be reformatted first. Which means of course it will be erased. If you want to keep old backups for some reason, you should get a new drive, and put the old one aside.

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Answer 2

den.thed

Level 10

90,916 points

Dec 14, 2025 7:58 AM in response to Thomoos

If you migrated from the old Mac, then you will need to start new Time Machine backup on that or a new external drive.

If you migrated from the old Time Machine backup, then you would have been given the option to Assume the old backups.

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