Trying to create bootable macOS Catalina USB for late model 2012 iMac from 2020 MacBook Air

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Level 1

5 points

Trying to create bootable macOS Catalina USB for late model 2012 iMac from 2020 MacBook Air

I have recently come into possession of an iMac which, after doing some research, is a late-2012 model, 27" . It is currently flashing a white screen upon boot with a prohibition symbol, which I figure means the macOS version on the bootable USB (MacOS Ventura 13.5) I am using is the wrong version. I used this version as it is the only thing in my applications folder, as my mac is an Apple Silicone model. I have found that macOS Catalina is the latest supported version for that 2012 iMac, so now I want to create a bootable USB drive with macOS Catalina on it. However, this seems very difficult, as the only place I can find macOS Catalina is on the Apple downloads page (Apple - Support - Downloads (AU)) , and that downloads as a .dmg file. After mounting this file, the .pkg file inside cannot be opened, as it is obviously too old for my MacBook. Now I am not sure how to go about getting this onto a bootable USB drive. Any help would be appreciated.

[Edited by Moderator]

Earlier Mac models

Posted on Dec 5, 2023 12:09 AM

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Answer 1

padams35

Level 4

3,613 points

Dec 5, 2023 3:47 AM in response to Brock-M

What dialabrain said.

You can only create USB installers with a Mac capable of using said installer.

To download Catalina for an installer you need an (intel) MacBookAir from 2012 to early 2020.

To download Sierra for an installer you need a MacBookAir from 2010 to 2017.

Your 2020 MBA is too new to download Sierra, and if it is the Late 2020 M1 then it is also too new to download Catalina.

You may need to find a friend with an Intel Mac to create an installer for you.

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Answer 2

HWTech

Level 9

67,286 points

Jun 28, 2024 12:05 PM in response to Brock-M

Do you have access to another Mac from 2007 to 2019? If so, then you can use that other Mac to download & create a bootable macOS USB installer using the instructions in the following Apple article:

Create a bootable installer for macOS - Apple Support

Generally you will need a Mac from:

2012 to 2019 (mid-2020) for macOS 10.15 Catalina
Late-2009 to 2017 (mid-2018) for macOS 10.13 High Sierra
2007 to 2015 for macOS 10.11 El Capitan

The other Mac can currently be running any version of macOS 10.6+. You can confirm the other Mac is compatible with the OS using the information in the following article:

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

Unfortunately, even if you had a copy of the full Catalina installer, your new M-series Mac would not be able to create the bootable macOS Catalina USB installer (personal experience since I have some archived older installers). It is very unfortunate that Apple makes this so difficult.

Your other option would be to boot into Internet Recovery Mode using Command + Option + R to attempt to access the most recent compatible online macOS installer (should be Catalina). However, some Macs may only boot to the older online installer for the version of macOS which originally shipped with the Mac from the factory. Plus the hack the previous owner performed may affect how Internet Recovery Mode behaves on this iMac. I would suggest first performing a PRAM Reset (hold the keys for the PRAM Reset) for at least three chimes, then immediately hold the keys for Internet Recovery Mode before the computer has a chance to attempt booting into the internal drive. You can just hold the Option key, then once at the Apple boot picker menu you can press Command + Option + R.

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Answer 3

WheelieNick

Level 8

45,771 points

Dec 5, 2023 1:13 AM in response to Brock-M

It is very hard to download older macOS versions on newer macs. You can download the sierra dmg from here and see if you can open that

How to download and install macOS - Apple Support

make a bootable drive with that one and after you’ve installed that on the old machine, update to Catalina from there

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Answer 4

Brock-M Author

Level 1

5 points

Dec 5, 2023 1:16 AM in response to WheelieNick

Oh I do understand what you're saying, since that is a different type of download, however after clicking the download Sierra link on that page I got the attached image. Any ideas? Thank you for your help.

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