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Will Time Machine overwrite existing data on external disk?

I have an external disk I use to access an older version of Mac OS. If I use this disk to backup my MacBook with Time Machine will it delete the OS files that are currently on the disk?

MacBook Pro 13″, macOS 10.15

Posted on Oct 15, 2021 10:51 AM

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Question marked as Top-ranking reply

Posted on Oct 15, 2021 11:09 AM

Brian Battles wrote:

I have an external disk I use to access an older version of Mac OS. If I use this disk to backup my MacBook with Time Machine will it delete the OS files that are currently on the disk?


Time Machine does best on it's own dedicated drive


Back up your Mac with Time Machine: https://support.apple.com/en-us/HT201250

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Question marked as Top-ranking reply

Oct 15, 2021 11:09 AM in response to Brian Battles

Brian Battles wrote:

I have an external disk I use to access an older version of Mac OS. If I use this disk to backup my MacBook with Time Machine will it delete the OS files that are currently on the disk?


Time Machine does best on it's own dedicated drive


Back up your Mac with Time Machine: https://support.apple.com/en-us/HT201250

Oct 15, 2021 11:06 AM in response to Brian Battles

More from OP:


To be clear, the MacBook runs on a current version of Mac OS. I can boot from the backup disk to access an older version of Mac OS and run some applications that do not work on more current versions. I want to backup my MacBook itself to an external disk...


I know that Time Machine creates folders to store the backups to the external disks. But will it delete ALL of the other files I already have on the external disk that have nothing to do with the backing up from Time Machine?

Will Time Machine overwrite existing data on external disk?

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