Failed recovery of 2010 iMac after a power outage

Unfortunately it seems Apple has turned off the servers for the older online macOS installers. Since this seems to be the case for you, then you will generally need access to another Mac from 2007 to 2018 to create a bootable macOS 10.11 or 10.13 USB installer.

macOS 10.11 -- generally need a Mac from 2007 to 2015

macOS 10.13 -- generally need a Mac from Late-2009 to mid-2018

You can use the information in the following article to confirm compatibility:

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

Here is an Apple with instructions for creating a bootable macOS USB installer if you have access to another compatible Mac:

Create a bootable installer - Apple Support

As for the online macOS installer not being available, you can provide Apple with product feedback:

Feedback - macOS - Apple

Edit: You can also use the original restoration DVD which shipped with the iMac from the factory which would then allow you to install macOS 10.11 (not sure about 10.13....you may need to get 10.11 on there first). Also, fully patch OS X 10.6.X since it may be needed to even install the later OS.

cawelch wrote:

Thanks again for your guidance. Before I try it, I wanted to make clear that the MacAir I am using to try to make the bootable installer on a USB Thumb drive is running the Monterey OS 12.7.2.

You should definitely be able to download the macOS 10.13 installer on the MBAir 2015 laptop.

You can also see which versions of macOS installer are available for this MBAir by using the following command in the Terminal app as it will list all of the available installers that can be downloaded on this MBAir:

softwareupdate  --list-full-installers

From the list of installers, you can use the command I posted in my previous reply to download the full installer by making sure the exact macOS version number is included at the end of the line in case I was incorrect about it being "10.13.6". Once the full installer has been downloaded to the Applications folder, you should be able to use the command you previously attempted to create a USB installer. Just make sure the command doesn't list any errors and shows successful completion. Plus make sure the "Install macOS High Sierra" application in the Applications folder is of the proper size (somewhere between 5 - 6 GB).

On my MacAir, there only seems to be one installer in the Utilities folder of Applications. It is very small, 1.7 MB and has the name iOS_App_Installer on it. There's one other file that has the word "installer" in the title of a pdf guide to its use. It has the file name AX88179_178A.dmg and the size of 175KB. So, I don't see a big installer (20MB, like you say) in my MacAir Applications file.

The macOS installer defaults to being downloaded to the Applications folder unless someone moves the downloaded application to another location. If only the stub installer is downloaded, then when you run the stub installer....many times the stub installer will download the rest of the installer to another location (not sure that is possible when running Monterey).

Theoretically @BDAqua's suggestion for Internet Recovery Mode (Command + Option + R) would be a good option for reinstalling macOS using the online macOS installer, but there have been many reports over the past few months that many people are no longer able to access servers providing older macOS online installers although the computers can be booted into Internet Recovery Mode. If it works for you, then great as it will make things easier.

Since a 2010 Mac would have shipped with macOS restoration DVDs from the factory, you can start with using the OS X 10.6 gray restoration DVD which originally shipped with your iMac to reinstall macOS as it may be the easiest way to get macOS reinstalled onto the iMac, although a very long & time consuming process.

After installing OS X 10.6.x from the original gray restoration DVD, you would need to install the later OS X 10.6 update patches. Then you will most likely need to download the macOS 10.11 installer using another computer (any more recent computer or OS is fine since the macOS 10.11 installer is available from outside of the App Store). Copy the macOS 10.11 installer .dmg file to a USB drive and transfer it to your iMac running OS X 10.6.x where you can mount the .dmg file and run the .pkg file to extract the real full installer into the Applications folder where you can run it and upgrade the iMac to macOS 10.11.

At which point, you should be able now be able to access & download the macOS 10.13 High Sierra installer from the Apple App Store and upgrade to macOS 10.13.6.

These are your various options for getting macOS 10.13 High Sierra reinstalled onto the 2010 iMac.

Start up from macOS Recovery

Option-⌘-R

Upgrade to the latest macOS compatible with your Mac.

In Disk Utility>View, select Show all Devices, highlight the top left entry.

APFS won't work for Sierra or earlier, Sierra or earlier needs MacOS Extended Journaled. High Sierra won't work for APFS on earlier Macs.

What has often worked for others is to use this Restore Method instead of CMD+r keys...

Option-⌘-R

Upgrade to the latest macOS compatible with your Mac.

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Do you have the full macOS installer in the Applications folder? Sometimes macOS may only download a 20MB stub installer instead of the full 5.x - 6.x GB installer. If this Mac where you have doing this is running macOS 10.14 or earlier, then delete the stub installer from the Applications folder and look on the root of the "Macintosh HD" volume (or whatever you may have renamed it) and look for a folder called something like "/macOS Install Data" and delete this as well. Empty the Trash & reboot. Try downloading the installer again...most likely it will just give you the stub installer again. If it does, there may still be a way of making it work, just let me know.

If you are using a Mac running macOS 10.15+, then delete the installer from the Applications folder & empty the Trash. You can then use the command line to download the full macOS 10.13.6 installer (assuming this Mac is really compatible with High Sierra). The following command will only work when using macOS 10.15+ on a compatible Mac:

softwareupdate  -d  --fetch-full-installer  --full-installer-version 10.13.6

Is this the Terms & Conditions just to begin the macOS installation process? Or has macOS been installed, and this is occurring during the first boot into the new OS?

If it is when booting into the new OS for the first time, then this is a known bug (at least to the regular forum contributors here). Go back so you do not sign into the AppleID. You must complete the process without signing into your AppleID. Once you have completed the macOS setup process, then you can log into your AppleID after you are fully booted into your macOS user account.

If this is occurring when beginning the macOS installation process, then are you booted from the USB installer? Can you scroll to the end of terms? Sometimes this is required before the Accept button is activated. For an older installer, maybe there is a check box to confirm acknowledge as well? Maybe try using another USB stick, especially a different brand since the quality of USB sticks is extremely poor. Or try rebooting the installer as I have sometimes seen things get stuck.