Create Bootable Installer for old MacOS (2012 Mac Pro) with M1 Pro MacBook Pro

<< run the .pkg file >> what is that?

The procedure is in this article, and as long as you name your USB stick exactly MYVolume and be sure to copy the ENTIRE command from the article (its laps over the edge of the page when displayed) and Paste it directly to the Terminal command-line, I don't understand why that would not work. (except for El Capitan, which is delivered differently)

How to create a bootable installer for macOS - Apple Support

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ah, here it is:

Safari downloads the following older installers as a disk image named InstallOS.dmg or InstallMacOSX.dmg. Open the disk image, then open the .pkg installer inside the disk image. It installs an app named Install [Version Name]. Open that app from your Applications folder to begin installing the operating system.

• macOS Sierra can upgrade El Capitan, Yosemite, Mavericks, Mountain Lion, or Lion
• OS X El Capitan can upgrade Yosemite, Mavericks, Mountain Lion, Lion, or Snow Leopard
• OS X Yosemite can upgrade Mavericks, Mountain Lion, Lion, or Snow Leopard

from:

How to get old versions of macOS - Apple Support

so the solution appears to be to select High Sierra.

Grant Bennet-Alder wrote:

<< run the .pkg file >> what is that?

FYI, That is how the macOS 10.11 El Capitan installer is delivered after opening & mounting the .dmg file. The .pkg file will extract & create the "Install macOS El Capitan" app within the Applications folder. Apple in their infinite "wisdom" (?) decided this can only be done on supported hardware. After all, why allow anyone the easy ability to create a bootable macOS USB installer using any system.

I did stumble across a site which had instructions for using the command line to extract & create the bootable macOS 10.11 USB installer manually, but it had a lot of steps some of which were confusing. Plus the resulting installer was not identical to the one which would be created using a compatible although it did work for me. I don't have the link handy. I know I did post a link to it a few years ago as did another contributor I think.

Thanks for that.

The original Poster mentioned trying Sierra and High Sierra. I am under the impression neither of those are inside a .dmg or involve .pkg files.

I think they should just work with the instructions from the article..

Grant Bennet-Alder wrote:

Thanks for that.

The original Poster mentioned trying Sierra and High Sierra. I am under the impression neither of those are inside a .dmg or involve .pkg files.

Actually macOS 10.12 Sierra is also downloaded from outside the App Store now as a .dmg file with a .pkg extractor app inside. I'll try to remember to look on my other computer later to see if I can find that link with instructions for using the command line to extract & create a bootable macOS installer. I think Apple may have changed something since then, so I'm not certain the instructions still work (I personally tested those instructions a year or two ago and they worked at the time).