MacOS – Change from Mac OS Extended File to APFS in order to install Mojave

high sierramac-minimacosmojave

I've tried to install Mac OS Mojave on my Mac Mini (late 2012), but it has Mac OS Extended (journaled) as the file system on the main drive. This link is somewhat inconclusive and refers to retired documents.

So my question is two-folded:

Can I change in-place from Mac OS Extended (journaled) to APFS on my boot disc (and can Mojave boot from APFS)?
If not, how can I install Mojave on my Mac Mini (which currently runs High Sierra)?

Update: I've already tried upgrading, and it failed with a vague error message related to the file system upgrade (which I sadly can't recall).

Best Answer

The internal drives of Macs are converted to APFS when upgrading to macOS 10.14 Mojave and yes, macOS Mojave boots from APFS just fine.

More specifically, when Mojave is installed it will convert any internal drive (including SSDs, HDDs and Fusion/Hybrid Drives) from HFS Plus to APFS.

This is an important distinction as prior to macOS Mojave, only SSDs were converted to APFS, and this explains some of the confusion over time regarding how macOS Sierra, macOS High Sierra and macOS Mojave have managed things as APFS has continued to evolve.

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MacOS – Terminal command to force-install Mac OS High Sierra onto a specified drive

This is independent of the RAID problem and may be independent of any APFS problem as well.

The core of this question is that the commanline will not allow you to redirect the install away from the booted drive. Therefore this answer covers the question as presented in the question headline.

The startosinstall command offers the switch --volume to redirect the installer onto a specified volume.

Try it:

..path/to/startosinstall --usage

and find that option missing.

It is there for any High Sierra installer.

BUT

This option is only presented when SIP is disabled!

The -–volume argument will be hidden, because startosinstall requires – at least – either CSR_ALLOW_UNRESTRICTED_NVRAM/0x40/64 or CSR_ALLOW_ANY_RECOVERY_OS/0x100/256.
Without one of these, the --volume argument won’t be supported.

That means also that using that switch from the Recovery partition it will be present every time.

This trickery is documented at Comparison of startosinstall's available options depending on boot OS environment

So in the case of this question:

/Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/startosinstall --converttoapfs NO --volume /Volumes/YourChoice

MacOS – External drive Mojave installs unaccessible from Mavericks

The simplest way to boot back to Mojave would be to reboot the Mac and immediately hold down the option key. This will invoke the Startup Manager. Select the Mojave startup disk. Next, click on the arrow below the icon to boot Mojave. If you wish to make Mojave the default, then hold down the control key before clicking on the arrow.

Apple a recently added new instructions for using the Startup Manager. These instructions can be found on the Apple website: How to select a different startup disk.

While it is technically possible to select Mojave directly from Mavericks, this would involve installing a third party boot manager such as rEFInd. Unless you intend to change operating systems often, such an installation would probably not be worth the trouble to pursue.

Best Answer

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MacOS – Terminal command to force-install Mac OS High Sierra onto a specified drive

MacOS – External drive Mojave installs unaccessible from Mavericks

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