Unable to Mac USB installer for Sierra

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Unable to Mac USB installer for Sierra

I am trying to make a bootable installer for MacOS Sierra for a MacPro 2010. URL How to download and install macOS - Apple Support

has link for Sierra but, the file it downloads is InstallOS.dmg and file in dmg file is InstallOS.pkg and not Install MacOS sierra. Link at I am trying to create a bootable Sierra o… - Apple Community

has terminal command to do this but file name in this command is Sierra.app, so I am unable to make to USB installer.

Can this terminal command be modified to work with the file downloaded from Apple called InstallOS.pkg or is there another link that can be used to download the proper file of Sierra.app as the terminal command specifies? Or perhaps just change it name? I have tried to use internet recovery but, for some reason it will not load, I only get a folder with a question mark. I have verified the wired keyboard is working properly. I have also tried reseting the SMC and reset PRAM. I assume that Apple has disabled this keyboard startup of **** Option Command R for this Mac model.

Any help would be appreciated.

Mac Pro, macOS 10.15

Posted on Sep 24, 2025 7:37 PM

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Answer 1

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HWTech

Level 9

68,210 points

Sep 24, 2025 9:52 PM in response to Brad Hyman

Did you read all of the instructions for how to download & extract the real installer from the downloaded DMG file in the first Apple article you linked? And @Eau Rouge's post in the second link you provided, reiterated the need to run the .pkg file to extract the real installer into the Applications folder.

I'm actually surprised to see the Sierra installer on the list in the Apple article containing the download links & article containing instructions for the command line. Apple actually removed the link for the macOS 10.12 Sierra installer years ago after some forum contributors alerted Apple that the installer was broken when creating a bootable USB stick. I'm wondering if Apple finally fixed the broken installer, or just forgot about why it had been removed. Crazy that a huge tech company could not be bothered to modify a single character to fix the problem and instead had to hide it from people.

Make sure the "Install macOS Sierra" app is found in the Applications folder. You cannot create a USB installer until that occurs, nor can you fix the installer until then.

FYI, you should try creating the USB Sierra installer without modification just in case Apple did finally fix it. I forget the exact error that would be encountered if Apple has not fixed it. IIRC it was an unusual error.

Just curious why you would want macOS 10.12 instead of 10.13 High Sierra? Any system capable of running 10.12 should be capable of running 10.13. A 2010 Mac can certainly run macOS 10.13 High Sierra.

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