[Hopefully this isn't something pre-announced that I just missed, but I did try to search for it first.]
We have a restriction on the the macOS High Sierra Installer and noticed starting on Tuesday a spike in the number of machines violating the restriction. All the Macs were running OS X 10.10.5, and I noticed that they had run Software Updates recently. When I check for updates the Macs, I see the following:
softwareupdate --list --all Software Update Tool Copyright 2002-2012 Apple Inc. Finding available software Software Update found the following new or updated software: * Install macOS High Sierra- macOS High Sierra ( ), 5106655K [recommended]
Apparently earlier this week Apple made High Sierra an UPDATE rather than an upgrade. This change appears to only be on OS X 10.10 Yosemite (presumably 10.10.5), as I had checked for this on OS X 10.9 Mavericks and OS X 10.11 El Capitan, and neither show "Install macOS High Sierra" when checking for updates.
If you don't want your Yosemite Macs to automatically upgrade to High Sierra, you can run this command:
softwareupdate --ignore "Install macOS High Sierra" This will prevent High Sierra from appearing in the Updates tab of App Store.app and from installing when running updates.
This is not an automatic upgrade, and is similar to behavior seen on El Capitan, where the Sierra installer was pushed:
Thanks @rtrouton. I haven’t tested it myself yet to see the prompting after the installer is downloaded, but if I recall, the Sierra installer download process was not transparent, you didn’t see it using softwareupdate and you couldn’t block it individually using --ignore like you seem to be able to with this one. Will test tomorrow.
Additional details after testing: If I run
softwareupdate --download --all it downloads the installer to /Library/Updates and leaves it there but does not run the update. If I then run
softwareupdate --install --all (or click the Update button in App Store.app) then it puts Install macOS High Sierra.app in /Applications and launches it. So, like Rich said, not an automatic upgrade.
Interestingly, after the installer is no longer in /Library/Updates or in /Applications (I deleted it), if I run
softwareupdate --download --all it no longer lists it as an available update.