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re-install Mac OS in recovery Mode will erase all Data ?

re-install Mac OS in recovery Mode will erase all Data ?

iMac 27", macOS 10.15

Posted on Jan 19, 2020 12:01 AM

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Posted on Jan 19, 2020 6:27 AM

To make clear what Mike Sombrio said above, if you tell the installer to erase or format the install location, then yes, all data on the install drive or volume will be erased. Otherwise it should only reinstall the macOS system files.


And his great advice to have a working backup before proceeding should be heeded.

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Question marked as Top-ranking reply

Jan 19, 2020 6:27 AM in response to cldjr

To make clear what Mike Sombrio said above, if you tell the installer to erase or format the install location, then yes, all data on the install drive or volume will be erased. Otherwise it should only reinstall the macOS system files.


And his great advice to have a working backup before proceeding should be heeded.

Jan 19, 2020 10:10 PM in response to D.I. Johnson

Thank you both.

Since an Apple Service Center has erased and install a new OS on my 2 weeks old iMac 2019 (finder was freezing with Music) I have a problem - error, error connecting, unknown error, unable to verify account name or password, your Apple ID or password is incorrect, there was an error in Apple ID preferences, Failed to authenticate please try again later.

All of this only with my ID on System Preferences (only)

Of course I have a back up but I already spend few days to re-install everything and I’m not so enthusiastic if I have to redo all this...

re-install Mac OS in recovery Mode will erase all Data ?

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