The softwareupdate command has some neat tricks up its sleeve, as pointed out by Armin Briegel: This command will download the most recent version of macOS, depositing it in your Applications folder: Thankfully, macOS installers can be downloaded via Terminal in macOS Catalina. However, I’ve run into a situation several times where the Software Update mechanism simply refuses to initiate a download:
Most of the time, you can re-download the current version of macOS via the Mac App Store, and older ones via these links:
