Partition Mojave HD to run Sierra

Started 5 months ago | Discussions thread
OP JohnNewman Contributing Member • Posts: 942
Re: Partition Mojave HD to run Sierra

JPAlbert wrote:


For 10.12 "Low" Sierra, format it for HFS+ (Mac OS extended with journaling enabled, GUID partition format).

Then download a copy of Low Sierra from Apple, see this page:

I believe this comes as a disk image. Open the image, launch the pkg file (I'm going from memory), and it will put the Low Sierra installer into your applications folder.

Then launch the installer and "aim it" at the EXTERNAL SSD (NOT the internal drive).

Firstly thanks to everyone who's replied. Much appreciated.

I've downloaded a copy of the Sierra installer and it now sits in my applications folder.

But when I try to launch it I get the message shown below.

Is there any way to over-ride this, maybe by holding down a combination of keys? I've tried a few combos but to no avail.

Thanks for your continued help,


Message when trying to open the Sierra installer.

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