Formatting Macintosh HD after installing OS X on external drive

My Mac stopped starting up properly a short while ago. After going through all the recovery and repair options I could find, including talking with an advisor, I installed the OS on an external hard drive.

I can now access the problematic internal hard drive in the Mac and have recovered everything not backed up.

My question is whether it is safe to format Macintosh HD and HD-Data if I am using the external for the OS and for startup?

iMac 21.5″, macOS 10.15

Posted on Dec 29, 2020 10:27 AM

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Limnos

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Posted on Dec 29, 2020 2:46 PM

It is. I just did that. If you're a super careful person you'll make sure you have two backups first just in case it was a hardware glitch that corrupted your drive and could possibly affect an external too. I had that happen about 20 years ago with Firewire drive.

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Formatting Macintosh HD after installing OS X on external drive

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