Longtime macOS users will know that even though the Mac has a built-in recovery partition, it’s always useful to have a dedicated USB drive with a macOS installer. I am a big fan of using a tool like DiskMaker X to create them to keep around if I need to wipe a drive and reinstall macOS quickly. If you have a drive created for Mojave, Sierra, and High Sierra, know that a certificate has expired. If you are getting an error similar to “This copy of the Install macOS Mojave.app application is damaged, and can’t be used to install macOS”, read on to learn how to fix it.
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