Install macOS Big Sur.app does not appear to be a valid OS installer application

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Level 1

12 points

Install macOS Big Sur.app does not appear to be a valid OS installer application

I am trying to create a bootable usb to do a clean install of Big Sur on my late 2013 Macbook Air (safely backed up for emergencies!) but when I try and use the terminal command copied and pasted from this article, it doesn't recognise the installation file downloaded from the app store as being a valid installation file (the exact error is "/Applications/Install macOS Big Sur.app does not appear to be a valid OS installer application").

Any help would be gratefully received. Tagged as a Big Sur issue but not sure if it is that or HighSierra.

Currently operating 10.13.6 HighSierra

MacBook Air 13″, macOS 10.13

Posted on Mar 13, 2021 9:33 AM

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Answer 1

Mar 13, 2021 9:40 AM in response to triciaruth

Try to download a fresh Big Sur full installer (maybe the old installer's certificate is expired). I guess High Sierra's Terminal should execute the command but I have not tried that in older OS X.

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Answer 2

Mar 13, 2021 9:46 AM in response to triciaruth

Please post the result of this Terminal command

ls -ledO@ /Applications/Install\ macOS\ Big\ Sur.app

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Answer 3

Barney-15E

Level 10

123,548 points

Mar 15, 2021 6:03 AM in response to triciaruth

What is the size of the "install macOS Big Sur.app"?

If it is not 11 to 12 GB in size, then it is the "stub" installer which downloads all the content when you install. You cannot make a bootable installer from the stub installer.

Essentially, you cannot download the full installer unless you already have that OS installed. You may be able to download the full installer using the command line and the softwareupdate command. I can never get the syntax correct, so I don't know specifically what to enter.

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Answer 4

Mar 15, 2021 7:13 AM in response to triciaruth

Those stub installers plagued High Sierra and I repeatedly got one of those when trying to make a USB flash installer from the full installer for a MacBook mid 2010 a few years ago. I ended up using macadmin-scripts for the download then.

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