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I also have an Intel iMac with a corrupted drive which fails to restore with recovery mode. I want to put Big Sur on a bootable fast drive and boot the iMac from that. I have not been able to download Big Sur to my M1 Mac Mini. If I try going through Apple Store it either says not found or not compatible with my system. I have not found any good direct link which allows me to just download the file! Please help!
Mac mini, macOS 13.2
erickdobrasil wrote:
First, thanks for the MDS suggestion, as it was the only way I could get ahold of Big Sur.
You're welcome. I believe it was @Old Toad who brought it to my attention originally.
One thing I didn't expect was that my iMac on this same menu gave me the option of restoring from a Time Machine backup.. It recognized the external drive I plugged in (LaCie drive) but it said it could not restore from this drive, that I would have to restore Big Sur first. I thought it would restore Big Sur and all my data from the Time Machine backup.
I don't use TM, but I believe this changed beginning with macOS Big Sur since macOS 11.x+ now has a signed & sealed read-only system volume, so now TM only backups of the user data & settings.
Signed system volume security in iOS, iPadOS, and macOS - Apple Support
After I restore my iMac I will see if I can get it to recognize the MDS created bootable flash drive (Samsung 128GB) from Recovery Mode, just to see whether that works.
If MDS has an option for creating a bootable USB stick as well, but you cannot get the system to recognize the USB as bootable, then try using the instructions in the Apple article to compare the results. This way it should tell you whether the fault is with the USB stick or the method of putting the installer onto the USB stick. FYI, you cannot just copy the installer app to the USB stick since it is just a regular application.
erickdobrasil wrote:
First, thanks for the MDS suggestion, as it was the only way I could get ahold of Big Sur.
You're welcome. I believe it was @Old Toad who brought it to my attention originally.
One thing I didn't expect was that my iMac on this same menu gave me the option of restoring from a Time Machine backup.. It recognized the external drive I plugged in (LaCie drive) but it said it could not restore from this drive, that I would have to restore Big Sur first. I thought it would restore Big Sur and all my data from the Time Machine backup.
I don't use TM, but I believe this changed beginning with macOS Big Sur since macOS 11.x+ now has a signed & sealed read-only system volume, so now TM only backups of the user data & settings.
Signed system volume security in iOS, iPadOS, and macOS - Apple Support
After I restore my iMac I will see if I can get it to recognize the MDS created bootable flash drive (Samsung 128GB) from Recovery Mode, just to see whether that works.
If MDS has an option for creating a bootable USB stick as well, but you cannot get the system to recognize the USB as bootable, then try using the instructions in the Apple article to compare the results. This way it should tell you whether the fault is with the USB stick or the method of putting the installer onto the USB stick. FYI, you cannot just copy the installer app to the USB stick since it is just a regular application.
With an Intel Mac, then boot into Internet Recovery Mode using Command + Option + R to access the online macOS installer. It is best to connect the Mac directly to the router using an Ethernet cable for a faster more reliable connection which also bypasses any hard to troubleshoot WiFi issues.
If it is a 2019+ model, then you can perform a firmware "Restore" which will reset the T2 security chip & firmware which will destroy all data on the internal SSD and prepare the internal SSD for macOS. Then you will need to boot into Internet Recovery Mode to reinstall macOS since the "Restore" may not push a clean copy of macOS onto the internal SSD. Usually for the Intel Macs you will only need the firmware "Restore" if installing macOS fails.
Otherwise you will need to find another Mac which is compatible with the OS you are trying to install so you can download & create the bootable USB installer using the instructions in this Apple article:
Create a bootable installer for macOS - Apple Support
I agree it is pathetic that Apple makes this process so difficult and requires very specific systems just to access the installers. Even when Apple provides an official download outside of the App Store, it still requires a compatible Mac to extract the real installer from the downloaded file. I don't see Apple changing this especially since with the Apple Silicon Macs Apple prefers either Recovery Mode or DFU Mode to Restore the OS.
FYI, even if you can download an older macOS installer, you won't be able to use an Apple Silicon Mac to create a bootable USB installer for anything other than macOS 11.x+ since the older installers are not Universal Binaries.
[Edited by Moderator]
What about 3rd party downloads? They may not be secure (since they aren't from apple) but if you've got no other option, you could get it from elsewhere? (won't work if your Mac shipped with Monterey or newer versions)
That's the problem. I tried several third party sites. One failed during download saying I exceeded their "free" download size limit. Another downloaded but did not contain "createinstallmediia" in the .iso file. I find it very frustrating you just cannot download an OS image easily from apple, especially since the software is free!
Thank you for the MDS reference. Finally I was able to download Big Sur onto my Mac Mini. I created a bootable installer using MDS on a flash drive. It had to be formatted as OS Extended filesystem to be recognized by MDS. When I formatted it with the AFPS filesystem the flash drive was NOT recognized. However, when I inserted the flash drive into my iMac and rebooted while holding down the Option key, it did NOT recognize the flash drive. What am I missing here?
Is the Intel iMac actually compatible with Big Sur? Big Sur is compatible with Intel iMacs from 2014 - 2020, or the iMac Pro (2017).
How did you create the bootable Big Sur USB installer? Using the instructions in the Apple article I linked or is there an option with the MDS app? You should be able to use the instructions in the Apple article as long as MDS provides the "Install macOS Big Sur" application. If this installer is not in the Applications folder, then you just need to modify the command in the Apple article so you are using the correct path to the installer app.
Try using another USB especially a different brand since the quality of USB sticks is extremely poor and Macs can be picky about the drives used for booting.
What is the exact model of your iMac?
First, thanks for the MDS suggestion, as it was the only way I could get ahold of Big Sur. While I was playing around with MDS I also tried (again) to restore my mid-2014 iMac using internet restore (old down Command-Option-R until spinning globe appears). After a while I get a menu where I could run DiskUtil and erase my corrupted iMac internal drive. I am now restoring Big Sur using the same menu. One thing I didn't expect was that my iMac on this same menu gave me the option of restoring from a Time Machine backup.. It recognized the external drive I plugged in (LaCie drive) but it said it could not restore from this drive, that I would have to restore Big Sur first. I thought it would restore Big Sur and all my data from the Time Machine backup.
After I restore my iMac I will see if I can get it to recognize the MDS created bootable flash drive (Samsung 128GB) from Recovery Mode, just to see whether that works.
You can try running this command in the Terminal…
softwareupdate --fetch-full-installer --full-installer-version 11.7.7
Thanks, I tried your suggestion but if fails with "update not found". Any other suggestion?
Not really. If your Mac mini shipped with Monterey or later you can't download Big Sur.
FWIW, MDS allowed me to download the Big Sur installer and create a bootable installer on an M1 MacBook Air. Is worth trying. It takes quite awhile to do but it worked for me.
erickdobrasil wrote:
Thank you for the MDS reference.
¥ou're welcome but it was HWTech that first brought it up.
How to download Big Sur to an M1 Mac Mini running Ventura
