Sometimes we need to install an operating system offline and need to install it on a USB drive.
I needed to update an iMac which came with macOS Mountain Lion and I was about to upgrade it via going through the updates via the AppStore and then I thought, just do it nice and clean.
So what did I do and what did I need:
- 8GB USB Drive which I formatted in Mac OS Extended (Journaled) using Disk Utilities
- Downloaded macOS Mojave which is just over 6GB in size from the AppStore
- A Mac to run the command below which can take up to 30 minutes or more to complete. So open terminal and run:sudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia –volume /Volumes/[YOUR DRIVE NAME] –applicationpath /Applications/Install\ macOS\ Mojave.app
- Then plug your USB into your Mac that you want to install the update, upgrade …
- Press power and when you hear the chime, hold down the command key until you get to the boot screen when you can select the USB you just created and now you are on your way.