This error is not very common with the users and appears only if the user is trying to erase their Macs and reinstall macOS High Sierra. Applications/'Install macOS High Sierra.app'/Contents/Resources/startosinstall -converttoapfs NO -agreetolicenseThe system will copy some files, then reboot, and you'll be able to start the installer (without APFS conversion) by booting the 'Boot macOS Install from.' Update scenario using 'startosinstall' After downloading the 10.13 installer, instead of running it, quit. If you're running Mojave, you will probably end up adopting APFS. You can use CCC (Carbon Copy Cloner) to clone from APFS to HFS+J, but that may be a fight you have to take on every update going forward. Apple has removed this option and will force APFS conversion. Note: This guide does not apply to macOS Mojave (or later). It is controlled by the ConvertToAPFS option in /macOS Install Data/minstallconfig.xml, which can be controlled by using 'startosinstall' from Terminal, or edited after the fact (see post #2). Fortunately, there a ways around this automatic conversion.
If your system drive is solid state, the installer will convert from HFS+J to APFS in both a fresh install scenario and an update scenario. As you already know, macOS High Sierra includes a new file system APFS.
