As was reported today, Apple is beginning to automatically download the macOS Sierra installer to compatible Macs. The installation process is not automatic, much like installing the macOS Sierra upgrade via the App Store. Instead, the macOS Sierra installation application will automatically download to /Applications.
Once finished downloading, the logged-in user will be alerted that the upgrade is available.
For environments where this automatic download is undesirable, there is a way to block it. For more details, see below the jump.
If you do not want the automatic download of the macOS Sierra installer application to occur, one important thing to know is that the Software Update function on the system in question must be set to automatically download updates in the background.
If this option is disabled, the macOS Sierra installer application will not download automatically.
You can manage this via the command line using the defaults command. To enable the automatic downloading of updates using the defaults command line tool, run the following command with root privileges:
defaults write /Library/Preferences/com.apple.SoftwareUpdate AutomaticDownload -bool TRUE
To disable the automatic downloading of updates using defaults, run the following command with root privileges:
defaults write /Library/Preferences/com.apple.SoftwareUpdate AutomaticDownload -bool FALSE
Update: 10-4-2016 – I made a mistake in my initial research of this issue, where I thought that the automatic check for updates needed to be disabled. Only the automatic download of updates needs to be disabled. Thank you to those folks who alerted me to the fact that I had the wrong information.
One other way to make certain that the macOS Sierra installer application will not download is to disable the automatic check for updates.
Without the automatic update check being enabled, the Mac will not check in for updates at all and background downloading of updates like the macOS Sierra installer application is automatically disabled.
Note: Disabling the automatic update check will also disable Gatekeeper, XProtect and SIP-related updates.
To control the automatic update check using the softwareupdate command line tool, run the following commands with root privileges:
To enable the automatic update check:
softwareupdate --schedule on
To disable the automatic update check:
softwareupdate --schedule off
You can also manage this using the defaults command. To enable the automatic update check using the defaults command line tool, run the following command with root privileges:
defaults write /Library/Preferences/com.apple.SoftwareUpdate AutomaticCheckEnabled -bool TRUE
To disable the automatic update check using defaults, run the following command with root privileges:
defaults write /Library/Preferences/com.apple.SoftwareUpdate AutomaticCheckEnabled -bool FALSE
