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DragonBluFly Author

Level 1

4 points

Installed Big Sur on external HD by mistake. How to rectify?

I clicked on the wrong drive when I installed Big Sur (from Mojave). So now my iMac (27" late 2015) is booting up from my external drive and my files were wiped in the process.

I do not use Time Machine but everything is backed up in a cloud.

How can I install Big Sur on my Mac HD and get it to book from the HD instead of the external HD?

I see that the install file for Big Sur is still on the Mac HD. Can I just run the installer again? Or what would be the best way to do it?

I realize that I will also need to chose from the Startup Disk where startup should be but I want to do this correctly. In what order should I do everything?

I plan to eventually boot up from the Mac HD, wipe the external HD and put back all my files onto the external HD, which is my original confirguration.

Thanks.

iMac 27″, macOS 11.1

Posted on Jan 13, 2021 1:15 AM

Best reply

dialabrain

Level 10

122,633 points

Posted on Jan 13, 2021 2:08 AM

DragonBluFly wrote:

How can I install Big Sur on my Mac HD and get it to book from the HD instead of the external HD?

I see that the install file for Big Sur is still on the Mac HD. Can I just run the installer again?

You can boot into the internal drive by restarting and holding the "option" key after the startup chime, or choosing the internal drive from System Preferences > Startup Disk and restarting. Then run the installer again.

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Installed Big Sur on external HD by mistake. How to rectify?

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