I’ve recently been given a 2011 iMac 21.5inch with a blank hard drive. This means that it has no operating system on. I’ve tried doing internet recovery but that failed and I can’t download older versions of Mac os on my newer MacBook as it is running montery. Is there any other way I can install Mac os or is there are specific reason why the recovery failed.
If have access to a Mid 2018 or older Mac (family? friends? acquaintances?) you can create a Bootable USB installer with High Sierra. How to create a bootable installer for macOS - Apple Support
Otherwise I'd suggest burning a Linux Live DVD to load onto the iMac. Obviously that isn't as good as running MacOS, but its better than having a computer with no OS.
You're going to have to install a system via CD disk. If you don't have the disks that originally came with the iMac you'll have to purchase OS X Mountain Lion - Apple from Apple and install that. After installing Mt. Lion you can upgrade that machine to High Sierra, 10.13. That's the farthest it can upgrade to.
2011 IMac os install
