I've made a boot disk from my late 2015 iMac running Monterey for my mid 2010 iMac to run El Capitan and it won't work

Hi there!

I'd reccomend that using the 2015 iMac, you create a macOS High Sierra bootable installer.

To begin, download macOS High Sierra here: How to download macOS - Apple Support, and follow these installation steps:

1. Click the link to open the App Store page for that macOS. 

2. In the App Store, click the Get button to begin downloading the macOS installer.

3. After downloading to your Applications folder, the installer opens automatically. Follow the onscreen instructions to install macOS.

After the installation app for macOS High Sierra is installed, follow the steps to create a macOS bootable installer: Create a bootable installer for macOS - Apple Support.

You can then use the bootable installer to reinstall macOS and erase the disk, if necessary.

Jack

You should have followed Apple's process for preparing the computer for transfer instead erasing it. Now, try restarting the computer in the Internet Recovery Mode. Press the Command + Option + R keys on restart to install the latest operating system that is compatible with that Mac.

I just got a mac mini m2 delivered and, somehow, screwed up resetting my imac (late 2015) for my daughter in law. Now the imac doesn’t boot as it cannot find the boot strap. The imac has a 1TB SSD.

When I try to get a High Sierra or later installer from the app store MacOS will not all it as it is not compatible with my M2 chip. Can someone help me please?

m2 Macs can't run High Sierra.

Start up from macOS Recovery

To start up from macOS Recovery, turn on your Mac and immediately press and hold one of the following combinations on your keyboard.

Command (⌘)-R

Install the latest macOS that was installed on your Mac.

Option-⌘-R

Upgrade to the latest macOS compatible with your Mac.

Shift-Option-⌘-R

Install the macOS that came with your Mac, or the closest version still available.