Refurb old Macs

[3s-gtech]

You can download an older version of OS X from a newer version - so if you have one of your models running High Sierra you can grab El Capitan from that. It downloads the installer for you, and you can do what you want with it. I refreshed a colleagues old Macbook (with a broken screen) to Lion this way a little while back.

[Tinribs]

But when I tried to do just that from the app store I got an error stating that my OS was too new and it wouldn't do anything else. If there is a way around that I would be grateful....

[3s-gtech]

It needs to be in your Purchased list first - a step I didn't mention. Then you can find it in the list, click Download and you'll get a prompt asking if you're sure. If it isn't in your Purchased list as you've never downloaded it, you may need to install an older version (from original discs if necessary) onto one of your newer iMacs, then step through the OS versions. It's a pain, but possibly the only way due to the jump in versions that you've made.

[Tinribs]

Unfortunately we only have El Capitan in our purchase list and we definitely don't have any original disks....

[3s-gtech]

https://apple.stackexchange.com/questions/286311/macos-sierra-doesnt-appear-in-my-purchased-list-within-the-mac-app-store

[Brimstone]

If you can get to a bootable El Cap installer, have you tried to boot the Mac using Windows with the USB Installer plugged in, just holding down the option key to get the drive and install El Cap?

[Tinribs]

We have success!

Thanks to Arthur who provided me with dmg files for various versions of the OS I managed to create a booting USB of Yosemite that actually installs. All I have to do now is physically move 300 Macs from the basement up three flights of stairs to the IT office for the builds.

Thanks to all for their suggestions..