I'm having problems upgrading my MacBook Air OS 10.9.5 to the newer version. It comes as corrupt image...What can I do?
FIRST, if you already have any upgraders for the Mac OS, either trash them or compress them. When downloading new versions of the Mac OS, you may have problems if an upgrader is detected to already exist.
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You may download the upgrader and find that it reports that it is "damaged."
It isn't.
What it has is an expired certificate. This can easily be fixed.
1. Go into the Applications folder.
2. Find the Installer for macOS in your Applications folder
3. Right-click (or Control-click) on the installer and choose “Show Package Contents”.
4. Open the folder named “Contents”.
5. Open the folder named “SharedSupport”.
6. Delete the file named “InstallInfo.plist”.
7. Enter your administer password to confirm.
8. Now the installer for MacOS will work perfectly.