Posted on 16th March 2018 by Hugo Costa

Is it possible to prevent conversion to APFS when upgrading to High Sierra?


While I was running a macOS Support Essentials 10.13 one of my delegates asked “Is it possible to prevent conversion to APFS when upgrading to High Sierra?” after explaining it to him I realised that most people in the room also didn’t realise this was an option, so I thought I better share it.

As most of you will know as part of the upgrade/install process to macOS High Sierra, the installer will convert SSD (Solid State Drives) drives from using the HFS+ (Mac OS Extended)  filesystem to the new default filesystem APFS (Apple File System), Rotational Drives and Fusion Drives won’t auto convert.

If you are one of the Mac admins that doesn’t want to convert yet, there is a way to install macOS High Sierra OS and skip the APFS conversion. Apple includes as part of the installer a command line tool named startosinstall.

startosinstall has a number of options, one of them is the –converttoapfs option, which can be used to prevent/force the conversion to APFS.

AmsysBlog:~ ladmin$ /Applications/Install\ macOS\ High\ –converttoapf NO

There is also a –nointeraction flag, that isn’t listed in the documentation, that automates the installation by suppressing all user interaction, including the –agreetolicense switch.

If you want to install to a different volume you can add the –volume flag to point to the volume required.

AmsysBlog:~ ladmin$ /Applications/Install\ macOS\ High\ –converttoapf NO –volume /Volumes/External


I hope you found this useful and would welcome any comments. The macOS Support Essentials 10.13 is a great way to get into the weeds and enhance your Mac support skills (and you can pick up an Apple certification). If you’re interested please drop us a line at