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Upgrading to Mojave via External Hard Drive

I want to upgrade my MacBook Pro from Sierra to Mojave. Rather than do a typical install, I want to clear the junk that has accumulated on my hard drive by wiping everything away and installing Mojave on a blank slate.


If I understand correctly, I can boot up from an external hard drive that I've cloned my internal hard drive to by holding down the option key while I restart my laptop. If this is true, then I assume I can work on my projects in my external hard drive while I'm installing Mojave on my internal drive.


I'm just a little uncertain how I should do this. Would I boot up via my external hard drive, then visit the App Store and access Mojave? If so, is there a way to tell it to install Mojave on my INTERNAL hard drive not the external drive I'm currently using?


Or is there a better way of doing it?


Thanks.


P.S. After I upgrade to Mojave, am I going to be able to access my external hard drives while they're still in Sierra mode? If not, I'll still be able to boot up with an external hard drive (Sierra) while holding down the option key, right? I just want to maintain contact with my Sierra files until I get all my apps and passwords migrated over to my internal hard drive.

Posted on May 18, 2019 8:41 PM

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Question marked as Top-ranking reply

Posted on May 18, 2019 9:01 PM

Chavista wrote:

I want to upgrade my MacBook Pro from Sierra to Mojave. Rather than do a typical install, I want to clear the junk that has accumulated on my hard drive by wiping everything away and installing Mojave on a blank slate.

If I understand correctly, I can boot up from an external hard drive that I've cloned my internal hard drive to by holding down the option key while I restart my laptop. If this is true, then I assume I can work on my projects in my external hard drive while I'm installing Mojave on my internal drive.



How to set up and use an external Mac startup disk - Apple Support

https://support.apple.com/en-us/HT202796


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4 replies
Question marked as Top-ranking reply

May 18, 2019 9:01 PM in response to Chavista

Chavista wrote:

I want to upgrade my MacBook Pro from Sierra to Mojave. Rather than do a typical install, I want to clear the junk that has accumulated on my hard drive by wiping everything away and installing Mojave on a blank slate.

If I understand correctly, I can boot up from an external hard drive that I've cloned my internal hard drive to by holding down the option key while I restart my laptop. If this is true, then I assume I can work on my projects in my external hard drive while I'm installing Mojave on my internal drive.



How to set up and use an external Mac startup disk - Apple Support

https://support.apple.com/en-us/HT202796


May 18, 2019 8:52 PM in response to Chavista

I assume I can work on my projects in my external hard drive while I'm installing Mojave on my internal drive.

No, the installer will take over and you can't do anything else.

If so, is there a way to tell it to install Mojave on my INTERNAL hard drive not the external drive I'm currently using?

When you run the installer, it asks where you want to install.

Or is there a better way of doing it?

Not to achieve what you want which is not possible.

The clone is likely the best choice, though.

P.S. After I upgrade to Mojave, am I going to be able to access my external hard drives while they're still in Sierra mode?

You should be able to boot into a drive with Sierra on it. That drive would not be able to see the Mojave drives as they will be APFS and Sierra cannot read an APFS volume. You can see the Sierra drive from booting into Mojave.

May 18, 2019 9:08 PM in response to Barney-15E

OK, I think I understand.


I'll just do the operation from my internal hard drive. Mojave will ask me where I want to install it (internal hard drive), and I assume it will also give me the option of erasing the internal hard drive and doing a fresh install.


After I've finished installing Mojave, I'll be able to access the files in my external hard drives (still running Sierra) and copy items to my main (internal drive).


Thanks.

Upgrading to Mojave via External Hard Drive

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