Trouble doing fresh install of macOS (from USB drive)

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Trouble doing fresh install of macOS (from USB drive)

Running into a bunch of trouble getting a fresh copy of macOS installed on my Intel Mac Pro 2019. I've read lots of forum posts and websites and I thought I followed the instructions. But it's not working unfortunately.

So I'm trying to do a fresh OS install from a bootable USB installer. I actually did have the latest Sequoia OS installed on this machine, but am trying to go back to Sonoma (due to some 3rd party apps not working correctly under Sequoia). I created the USB bootable installer (using the terminal command line tool). I have been able to use the USB installer on another computer, so I think it's ok.

I thought I had the right process.. but maybe not. I booted into Recovery (Command + R) and when I got into that, I went into disk utility and wiped my Macintosh HD. Reformatted it with the same name. Then I was going to do the OS install. On that list in Recovery it said to install Sequoia (which I don't want) so I rebooted the computer again and this time held down Option to boot to the USB installer. I see that drive and select it, but then I get stuck in a 'Internet Recovery' loop and never can actually get Sonoma installed.

What did I do wrong? Should I be booting back into Recovery (Command + R) or just holding down Option and booting to the USB bootable installer? What should I do now?

I did go into the 'Startup Security Utility' previously and adjusted those settings. I did change the setting so that I could boot to external USB drives. I also did try setting the Secure Boot settings to a lower level to make things go easier. I set it to 'No Security' in hopes that the re-install would be easier (and I know I have a good and proper installer that I downloaded from Apple on the App Store).

Well that is where I'm at. I think I had to wipe the Macintosh HD right? But now it seems like it is having trouble starting the Sonoma OS installer from the USB drive. What am I doing wrong?

Thanks so much for any help.

-Peter

Mac Pro (2019)

Posted on Jan 29, 2025 10:57 AM

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Answer 1

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prberg Author

Level 1

10 points

Feb 2, 2025 4:33 AM in response to HWTech

Thank you for the help. I did mange to get it resolved and I got Sonoma Installed. I think I didn't originally try just Option booting to the USB installer because when I did option boot to that drive, it did show the USB installer drive and I selected it. But then it just got stuck on a screen with a globe icon and a list of my wifi networks (and I didn't know what that screen was about or what I was supposed to do). I did have it plugged into ethernet.. but I guess I had to login to my wifi network for some reason (I read later that it still needs to access the internet when the drive has been wiped.. to download or confirm a few small things?). So that is when I tried booting into Recovery Mode but wasn't able to easily start the install.

I wish the screens might have better info about what is happening or needs to happen so it could be more clear to the user. So I did end up connecting it to my wifi and then it launched into Internet Recovery. I just let it go and sometimes it gave me an error, but eventually it seemed to download what it needed to and I got to the screen that let me choose to install Sonoma from the USB drive.

None of the instructions I found for doing this downgrade really mentioned anything about Recovery mode, or needing to connect to the internet with my wifi to download or confirm stuff from the Apple servers. Seems like maybe this process could be easier.. but at least I got it resolved after enough trying.

Thanks for your help.. I really appreciate it.

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Answer 2

HWTech

Level 9

68,702 points

Jan 29, 2025 1:27 PM in response to prberg

My guess is you wiped out the customized security settings to allow booting from USB when you erased the internal SSD, then rebooted. If you had booted from the USB installer when you erased the internal SSD, then I think you would have been Ok.

At this point your only option is to use Internet Recovery Mode to install either the OS which originally shipped with the laptop from the factory using Command + Option + Shift + R (likely Mojave or Catalina), or install Sequoia with Command + R, or Command + Option + R (In your specific circumstance these are equivalent). If you choose the first option you can then upgrade directly to Sonoma. Or using either method, you will at least have the ability to use the Startup Security Utility to allow booting from USB again so you can perform a clean install of Sonoma....just make sure to boot from the USB Sonoma installer this time ;-)

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