The createinstallmedia command will fail with the new Sierra installer. To learn how to perform a clean installation of macOS using the bootable USB drive method, click one of the following links: macOS Catalina, macOS Mojave, macOS Sierra.

You can find the latest official download links below for the last six versions of Apple's Mac operating system, all of which contain a new certificate that has not expired: Doing so will also ensure that you have all of the macOS updates that have been released since you made the original installer, meaning you won't have to update macOS immediately after the initial installation is complete. To fix the damaged installer, you should just download the installer again. If you tried to use a macOS installer in the last few days or weeks, you may have been met with an error message saying something like ' This copy of the Install macOS Mojave.app application is damaged, and can’t be used to install macOS.'Īs Apple explains in a newly published support document, the likely reason for the 'damaged' error message is an expired certificate. If you tried to run your installer recently and unexpectedly received an error that it is damaged and can't be used, then don't worry – keep reading for a simple and straightforward way to fix it. We need to move the operating system files to the installer app directory /Applications/Install macOS High Sierra.app/Contents/SharedSupport.Creating a macOS installer on a bootable USB drive provides a convenient way of installing a fresh copy of macOS on multiple Macs, and also allows you to perform a clean installation quickly and easily. We’ll close the installer now (using the ⌘ + q keyboard shortcut) and move on to creating our bootable USB disk. The installer will prompt you to restart your machine once it has completed downloading. These files are what we need to create our bootable disk. In the mean time, you can access these downloaded files at the /macOS Install Data directory. You’ll have to wait for this download to finish. It will download an application called Install macOS High Sierra and launch it.Ĭontinue the steps as prompted by the installer until it starts downloading the actual operating system’s files:

Then fetch the installer by going to macOS High Sierra on the App Store and pressing the Download button. Choose Mac OS Extended (Journaled) for the file system format and set the name to Untitled. To start, find a USB drive that is big enough (8 GB should work) and erase it using Disk Utility. It wasn’t immediately obvious to me how to do that, so I wrote the steps down if you’re looking to do the same. Due time for an upgrade!īecause I want to start from a clean slate and erase my entire drive, I needed a High Sierra bootable USB drive to install from. I was still running on an embarrassingly old version of Mac OS X when macOS High Sierra was released.

Install sierra from usb