Some times you get your hands on an Apple computer that is years out of date. Depending on what the system is doing you may need to take incremental steps to update the system to newest version of MacOS.
By Default the Apple App store wants to jump to the newest version of MacOS.
Starting in MacOS Catalina 10.15.6 Apple updated the SoftwareUpdate terminal utility to download the installers for supported versions of MacOS. The utility downloads the offline installer to the Applications folder and then it can be copied to the system that needs it.
- Open the Terminal
- Get list of supported MacOS versions
type: softwareupdate –list-full-installers
- Download the Installer (High Sierra Example)
type: softwareupdate –fetch-full-installer –full-installer-version 10.13.6
- Wait for the download to finish
- You’re done!
And if you run into any issues, you can always use –h to open the help screen.