Bootable Startup Drive Problem

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Al Hatch Author

Level 2

216 points

Bootable Startup Drive Problem

How do I create an HFS bootable startup drive for Intel?

Here are my steps on an Intel iMac running Big Sur:

Format an external HDD as Mac OS Extended (Journaled) using GUID Partition Map.
Tell Install Disk Creator (or Terminal) to make this drive a bootable Mojave startup drive.
Success!

Except… Install Disk Creator and Terminal both insist on reformatting the target drive as APFS.

Problem: APFS is designed for SSDs. It will thrash-and-trash HDDs.

Is there no way to create an HFS bootable startup drive for Intel on Intel?

Thanks.

iMac Line (2012 and Later)

Posted on Oct 16, 2022 5:51 PM

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Answer 1

Best reply

HWTech

Level 9

56,234 points

Oct 16, 2022 6:21 PM in response to Al Hatch

I'm a bit confused here. You can create a bootable macOS USB installer using the instructions in this Apple article:

How to create a bootable installer for macOS - Apple Support

If you are installing macOS 10.13+, then macOS will insist on using APFS for the boot drive. At one time it was possible to install macOS 10.13 (and possibly 10.14) and retain the HFS+ volume, but this required a modification to a file on the USB installer. You should be able to find instructions if you search online.

However, macOS 10.15+ requires an APFS volume for the boot drive and there is no way around it.

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Answer 2

Al Hatch Author

Level 2

216 points

Oct 16, 2022 6:56 PM in response to HWTech

That's what I was afraid of.

One application I need will run on nothing later than Mojave 10.14.6.

Booting into macOS from an external drive is not my problem. That's easy.

What I wanted was to have that external drive HFS+. You have confirmed that it is not possible.

I'm going to abandon the HDD for this.

Thanks.

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Answer 3

Oct 17, 2022 1:01 AM in response to Al Hatch

A workaround is to install Mojave on an APFS volume. Then use Carbon Copy Cloner to clone it to a Mac OS Extended volume. It will boot and work otherwise OK but subsequent Mojave point updates do not work.

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Answer 4

Oct 18, 2022 12:06 AM in response to Al Hatch

Mojave point updates do not work on Mac OS Extended. AFAIR they do not appear in the update panel. But there are no longer Mojave updates anyway (maybe some Safari update a long time ago). A workaround might be to use Carbon Copy Cloner to clone to APFS, do the Mojave update, and clone back to Mac OS Extended.

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