Partition Mojave HD to run Sierra

Started 2 months ago | Discussions thread
JPAlbert Senior Member • Posts: 1,068
Re: Partition Mojave HD to run Sierra

OP:

OK, we need to try something else, no promises.

You may want to print this out first.

1. Power down, all the way off
2. Now we're going to boot to a special version of internet recovery:
3. Press the power on button and IMMEDIATELY hold down:
Command-shift-OPTION-R
4. This will get the Mac booted and then should offer you the original version of the OS that was shipped with the MBair in 2017. Everymac.com says that this is OS 10.12.5.

5. Once you get booted, does it offer you the "Sierra" installer?
6. If so, start "clicking through"
7. REMEMBER -- at the appropriate moment, when the installer asks WHERE you wish to install, "point it" at the external drive.

Does this work?

If it does, go ahead and get a basic account set up. Then you may need to go to the Apple Software Updates.

There is the Sierra 10.12.6 "combo" updater:
https://support.apple.com/kb/DL1931?viewlocale=en_US&locale=en_US

And there may be a security update to install as well.
IMPORTANT -- there may be MORE THAN ONE security update, but I think the only one you may need might be the "last" of them. Investigation is needed.

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