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I downloaded the Mojave installer from the App Store and copied it to a USB stick like so:

$ sudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia --volume /Volumes/UNTITLED --nointeraction

Previous to that I formatted the USB stick with the option Mac OS Extended (Journaled) from the Disk Utility app.

The problem is that when I start the computer holding the Option key it shows three options to boot from, one is my disk drive, the other is the Mojave installer in the USD stick, and there is also a suspiciously named Windows option.

If I pick the Mojave installer it reads the USB stick and shows the progress bar that appears when the systems is starting but it takes too long and it quickly stops reading the USB stick. It also doesn't show the installer app after it reaches 100% of the progress bar.

If I try to start from the Windows option I see a black screen showing an EFI error, but I have never tried to install Windows on my computer, so I'm not sure what that option is trying to do.

How long does it takes to show the Mojave installer app when starting from the USB stick?

Is it ok if the USB stick stops showing activity after a couple of minutes while the progress bar is still below 20% or 30% after the Mojave installer is selected from the boot loader?

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  • You can run Disk Utility to see if there is a bootable Windows Partition. Unless you are missing a lot of HD space I'd just ignore it. If your Mac is USB 2 then booting the installer could take quite a while (10 - 15 min, maybe). Try creating the installer with DiskmakerX and see it behaves better then. – Steve Chambers Sep 8 at 21:12
  • @SteveChambers Thanks. I just finished upgrading from the USB stick, I'll try now a fresh install, which is what I was trying to do in the first place. It's a MacBook Air Mid-2012. – rraallvv Sep 8 at 21:29
  • Boot up without the USB or Unplug the usb during that screen to see if the windows partition is on the USB or not. Booting from the installer via usb can take a very long time and sometimes the progress bar isn’t very accurate. You can boot the installer in verbose mode to get more detailed information about the process. Good option to get to the boot screen, then hold cmd+V while choosing the installer. Running “diskutil list” in terminal will display all your HD’s (internal & external) information. – Theologin Sep 8 at 23:12
  • @Theologin the boot menu shows only the hard drive, the windows partition and the Mojave installer appear only after I plug in the USB stick. Thanks for the tip about the verbose mode. – rraallvv Sep 9 at 1:45
  • @Theologin the installation process in verbose mode shows the message Creating RAM Disk for /var/db and it gets stuck without showing any error. – rraallvv Sep 9 at 2:44

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