Downloading installer and making a thumb Drive to install an older OS X

I went to this page> How to download macOS - Apple Support

I clicked on High Sierra and saw this:

but when I clicked "Get" I received this:

I tried the same steps again with Mojave. it DID start downloading. (which I then cancelled)

but here's the rub. my machine shipped with Catalina, so Mojave should have been a no-go. but I have seen others here saying that you may be able to download the macOS prior to the shipping version if the Mac was available with said version when first manufactured. and the 2019 27" iMac could have been had with Mojave when first built.

so I must say, the jury is still out on this.

MartinR wrote:

I am also curious about any sources or documentation that claims the above cannot be done. If anyone can provide links to that info I'd like to be able to read it.

on the How to download macOS - Apple Support page, in the "If you need help" section near the bottom of the page is one place where that info can be seen.

but apple used the Qualifier "might" two times in the documentation. (which I never really noticed before)

so apparently, it MIGHT work sometimes and sometimes not.

That's true if one is attempting to install macOS on the machine. You cannot install a version of macOS that predates the manufacture of the subject Mac and the version of macOS that originally came with it. So, yes, if you want to install High Sierra on a Mac, that Mac must have been capable of running High Sierra in the first place.

But regarding creating bootable installer disks, I think those rules are not in play.

If the user downloads the macOS installer via the proper Terminal command** & uses the proper Terminal command to create the bootable installer, the version of macOS running on the Mac creating the bootable installer should be irrelevant. That is, once a macOS installer is downloaded successfully, a brand new Ventura Mac should be able to create a bootable installer for any of the downloaded macOS installers.

I could be wrong here, but since I was able to create a bootable Catalina installer using my newer Monterey iMac, I'm going to test creating a High Sierra installer also.

** The command: softwareupdate --fetch-full-installer --full-installer-version **.**.*

where **.**.** is the numeric version of macOS that you want to fetch (download)

Catalina would be: softwareupdate --fetch-full-installer --full-installer-version 10.15.7

And the command to create the bootable installer for Catalina would be:

sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

where /MyVolume needs to be replaced by the name of the flash drive

the only thing I can add here, is that to create a bootable installer, you need to use a Mac that is compatible with the OS X / macOS that you are trying to create the bootable installer for. meaning that, if you want to create a High Sierra bootable installer, the host Mac MUST be capable of running High Sierra. or also, if you try to create a High Sierra bootable installer on a Mac that shipped with Big Sur, you WILL NOT be able to create a High Sierra installer on that Mac.

albertfromedmonton wrote:

"I am using a newer iMac with Ventura"

Exactly what model iMac is this? Check Apple > About This Mac and tell us what it says.

"Entering the commands in the terminal are not working either."

"I can't get pass the password. "

You must be logged into your Mac as an administrator to run these commands, and use your admin password.

Please tell us exactly what commands you used.

MartinR wrote:

But regarding creating bootable installer disks, I think those rules are not in play.

that is a nice thought. I need to leave right now, but I will test that theory later today and post back with my results.

I tried downloading the High Sierra installer but it is gone. It's no longer in the list of available installers and when I tried a workaround by doing softwareupdate --fetch-full-installer --full-installer-version 10.13.6, I got a message that the update was not found. Cannot proceed with the test at present. Catalina & Mojave are still available, however.

jeffreythefrog wrote:

but here's the rub. my machine shipped with Catalina, so Mojave should have been a no-go. but I have seen others here saying that you may be able to download the macOS prior to the shipping version if the Mac was available with said version when first manufactured. and the 2019 27" iMac could have been had with Mojave when first built.

If the specific Mac model existed before the release of an OS, then as long as there were no changes to that model, then it can run the previous OS. For example, a Mac, lets call it model A is being sold with Mojave in July and this exact same model A Mac is still being sold after the release of the next OS which in this example would be Catalina, then the model A Mac can have macOS Mojave installed since the hardware has not changed since July. Now if Apple releases a slight update to model A at the time of the next OS release, that model will only be able to run Catalina and that model will have a new name such as Model B in our example. Model B cannot be downgraded to Mojave, because Model B never ran Mojave no matter that the difference between Model A & Model B may be ever so slight such as a slightly faster CPU.

As far as creating a bootable macOS installer, this can only be done using a Mac which is compatible with the OS you are trying to create (aka a Qualifying Mac). There are a few older installers which are now available to be downloaded from outside the App Store....these installers can be downloaded using any computer, however, you will need a Qualifying Mac to run the included .pkg file to extract the real installer into the Applications folder. It also appears you may need to use a Qualifying Mac even to run the Terminal command as I cannot create any older macOS USB installers on an M1 Mac even though I have the full installer app available. Even though I downloaded Catalina on an older Mac and stored it in a .dmg archive so I will always have access to it, I cannot run the Terminal command "createinstallmedia" while on an M1 Mac which can only run Big Sur or later. I don't think this is an M1 thing, but just more of the needing a Qualifying Mac to do the job (silly that Apple makes things so complicated & difficult since everyone does not have access to another Qualifying Mac).

To create a bootable macOS 10.15 USB installer, the OP will need to use a Mac from 2012 to 2019. There may be an exception or two so you can use the information in this article to identify exactly which Macs are compatible with 10.15 and use one of them to download & create a bootable macOS USB installer:

https://eshop.macsales.com/guides/Mac_OS_X_Compatibility

Of course the OP has several other options. If they have access to a Qualifying Mac for macOS 10.11, then they have more options available to create a bootable macOS 10.11 installer as that generally requires a Mac from 2008 to 2015. Or if they can boot into Recovery Mode using Command + Option + R, then they can reinstall macOS 10.8 Mountain Lion in order to get a booting Mac, after which they can access any of the later macOS installers up to & including 10.15.

Also, the "softwareupdate" command may not have access to all the options for downloading the full macOS installer on some older versions of macOS (on some it may be available, but it is not noted in the help/info for that command).

HWTech wrote:

If the specific Mac model existed before the release of an OS, then as long as there were no changes to that model, then it can run the previous OS. For example, a Mac, lets call it model A is being sold with Mojave in July and this exact same model A Mac is still being sold after the release of the next OS which in this example would be Catalina, then the model A Mac can have macOS Mojave installed since the hardware has not changed since July. Now if Apple releases a slight update to model A at the time of the next OS release, that model will only be able to run Catalina and that model will have a new name such as Model B in our example. Model B cannot be downgraded to Mojave, because Model B never ran Mojave no matter that the difference between Model A & Model B may be ever so slight such as a slightly faster CPU.

that was my understanding. thanks for confirming that for us.

As far as creating a bootable macOS installer, this can only be done using a Mac which is compatible with the OS you are trying to create (aka a Qualifying Mac). There are a few older installers which are now available to be downloaded from outside the App Store....these installers can be downloaded using any computer, however, you will need a Qualifying Mac to run the included .pkg file to extract the real installer into the Applications folder. It also appears you may need to use a Qualifying Mac even to run the Terminal command as I cannot create any older macOS USB installers on an M1 Mac even though I have the full installer app available. Even though I downloaded Catalina on an older Mac and stored it in a .dmg archive so I will always have access to it, I cannot run the Terminal command "createinstallmedia" while on an M1 Mac which can only run Big Sur or later. I don't think this is an M1 thing, but just more of the needing a Qualifying Mac to do the job (silly that Apple makes things so complicated & difficult since everyone does not have access to another Qualifying Mac).

yeah, I was pretty sure about that as stated in my very first reply to this discussion. thanks again. :)

Getting back on this subject.

I can confirm that I was able to create a High Sierra 10.13.6 bootable installer flash drive using a 2019 Intel iMac that originally shipped with Mojave 10.14.4 and now has Monterey 12.6.1. This model (iMac 19,1; A2115; EMC3194 was released 19-Mar-2019. macOS Mojave was released 6 months earlier on 24-Sep-2018, so this particular iMac was never qualified to run High Sierra.

The predecessor model was a mid-2017 iMac 18,3; A1419; EMC 3070 with a different CPU, different RAM, etc. - so the 2019 model is not a 'carry-over' that theoretically could have run High Sierra.

I wanted to see if this could be done because I have repeatedly heard from other members that one could not download or create a bootable installer of a version of macOS that the downloading/creating Mac itself wasn't "qualified" to run. My experience disproves that. (I would point out, however, that this is a purely Intel iMac - no T2 chip; and it's clearly not Apple Silicon - those models may behave differently.)

I am also curious about any sources or documentation that claims the above cannot be done. If anyone can provide links to that info I'd like to be able to read it.

MartinR wrote:

I can confirm that I was able to create a High Sierra 10.13.6 bootable installer flash drive using a 2019 Intel iMac that originally shipped with Mojave 10.14.4 and now has Monterey 12.6.1. This model (iMac 19,1; A2115; EMC3194 was released 19-Mar-2019. macOS Mojave was released 6 months earlier on 24-Sep-2018, so this particular iMac was never qualified to run High Sierra.

I wanted to see if this could be done because I have repeatedly heard from other members that one could not download or create a bootable installer of a version of macOS that the downloading/creating Mac itself wasn't "qualified" to run. My experience disproves that. (I would point out, however, that this is a purely Intel iMac - no T2 chip; and it's clearly not Apple Silicon - those models may behave differently.)

I am also curious about any sources or documentation that claims the above cannot be done. If anyone can provide links to that info I'd like to be able to read it.

You cannot download an OS from the App Store which is not compatible with the system. I thought I had tried it years ago. While it is possible to download macOS 10.12 and earlier from links outside of the App Store these days, the downloaded file can only be run on a system compatible with that OS....I have verified this myself.

I do know on Apple Silicon Macs that it is impossible to use the "createinstallmedia" command on a previously downloaded macOS installer for an OS that predates the Apple Silicon Macs such as macOS 10.15 (Apple Silicon Macs shipped with macOS 11.x+. Another long time respected forum contributor brought this to my attention and confirmed it as well. I would have assumed that it should be possible to create the USB installer using any Mac, but for some reason at least with Apple Silicon Macs this is not possible....I have not tried the same with an Intel Mac...I do have access to an older Intel Mac which is not compatible with Monterey or Ventura which I can test.

For some reason Apple just cannot create a simple method of downloading an installer from any computer and using simple everyday tools/utilities create a bootable USB installer regardless of the OS or computer being used.

While it is possible to download macOS 10.12 and earlier from links outside of the App Store these days, the downloaded file can only be run on a system compatible with that OS....I have verified this myself.

Yes, insofar as running the installer file on the Mac in order to install macOS. But what I wrote about was running createinstallmedia on a Mac running Monterey that itself could not run High Sierra but still was able to create a High Sierra bootable installer.

On the other hand, maybe I didn't understand your reply.

No, you understood. I just wanted to add that clarification to the process. Nice to know that the "createinstallmedia" is not as restricted on Intel Macs as it is on the Apple Silicon Macs.