I'd like to revert to High Sierra from Mojave via Time Machine. I've already wiped the drive and installed a Mojave Time Machine backup, but I'd like to go back even further. The presence of what directory or file in the Time Machine history will be indicative of whether Mojave or High Sierra is installed?

Thanks

  • 2
    Walrus - it's not gonna happen unless you have a TM from before the upgrade. See apple.stackexchange.com/questions/271104/revert-to-el-capitan & apple.stackexchange.com/questions/309399/… – Tetsujin Nov 12 at 19:17
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    FYI, for rolling back Mac OS upgrades, restoring a backup taken with CarbonCopyCloner is much more complete than restoring from Time Machine backup. CarbonCopyCloner makes a full bootable backup. You can also use it to "try out" a new OS version on an external hard disk. (I'm not affiliated in any way, but knowing about CCC is vital for Mac power users in my opinion.) – Wildcard Nov 12 at 20:46
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    I think the question is pretty clear. OP wants to remove all the time machine backups that were made under Mojave. In order to clearly differentiate between Mojave and High Sierra backups, OP would like to look for the presence of a file that should exist under Mojave but should not exist under High Sierra. – Wowfunhappy Nov 13 at 0:37
up vote 9 down vote accepted

From what the question seems to imply:

the most significant file that the macOS system writes for itself is perhaps its own version number file?

That file is located at

/System/Library/CoreServices/SystemVersion.plist

If that file contains, for example:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
        <key>ProductBuildVersion</key>
        <string>16G1618</string>
        <key>ProductCopyright</key>
        <string>1983-2018 Apple Inc.</string>
        <key>ProductName</key>
        <string>Mac OS X</string>
        <key>ProductUserVisibleVersion</key>
        <string>10.12.6</string>
        <key>ProductVersion</key>
        <string>10.12.6</string>
</dict>
</plist>

Then the above is for Sierra 10.12.6.

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