I wrote a tool that sniffs changes to macOS defaults as they change and autogenerates the defaults incantation to set those preferences. I have a post in the wings about this. For that to be useful, though, I need to establish a bit more groundwork about defaults. In particular, the various locations where the backing plist files can exist. Most are intuitive, but many are not.
Here’s a rundown of places where defaults plist files can exist if they’re not in ~/Library/Preferences or /Library/Preferences.
Host-specific
A default may be “host-specific,” meaning it only applies to a specific machine. I believe the idea is to allow per-machine configuration in situations where a user’s preferences are loaded from a synchronized folder or network share (such as an LDAP directory or NFS home directory). In this case the preference will be under a UUID that is specific to the given machine. Looking under ~/Library/Preferences/ByHost, you should see a number of plist files each with a UUID in its name. Using defaults to apply a setting to the local machine, use the -currentHost option. Further, the UUID in the plist file name is omitted from the defaults domain. The screen saver preference is an example. A change to: ~/Library/Preferences/ByHost/com.apple.screensaver.2DDBD5D3-ADCF-4EB4-AC37-285A5079813B.plist
…could be accomplished with:
$ defaults -currentHost write 'com.apple.screensaver' 'moduleDict' -dict-add 'path' '<string>/System/Library/Frameworks/ScreenSaver.framework/Resources/Computer Name.saver</string>'
$ defaults -currentHost write 'com.apple.screensaver' 'moduleDict' -dict-add 'moduleName' '<string>Computer Name</string>'
NSGlobalDomain
When the preference domain is the NSGlobalDomain, the default isn’t stored in a domain specific to an application or preference pane. These defaults are visible to all applications, regardless of their own preference domains. Locations where global preferences may be recorded include:
/Library/Preferences/.GlobalPreferences.plist~/Library/Preferences/.GlobalPreferences.plist~/Library/Preferences/ByHost/.GlobalPreferences.plist
If it isn’t clear where a preference is being recorded, try one of these locations.
Multiple plist files
In some cases, a single setting in a user interface may actually manifest across multiple plist files. An example of this is the Trackpad preference pane.
Trackpad preferences.
The “Tap to click” setting is stored across the following three domains:
com.apple.driver.AppleBluetoothMultitouch.mousecom.apple.AppleMultitouchTrackpadNSGlobalDomain(under thecom.apple.mouse.tapBehaviorkey)
On a MacBook, settings in all three of these domains are required to configure tap-to-click.
Containerized Applications
Apps that are containerized (such as any app from the Mac App Store) can only write files inside their own containers. App containers are located in ~/Library/Containers. For example, TextEdit.app’s container is /Library/Containers/com.apple.TextEdit, and it’s preferences are written in Data/Library/Preferences/com.apple.TextEdit.plist inside that directory.
This can get confusing; in some cases a previous, non-containerized version of the app may have written its preferences to ~/Library/Preferences. So there may be a plist file there that is no longer in use.
So that’s a summary of preference locations on the filesystem that may be less than obvious. In the next post, I’ll describe a tool that will work out for you what the defaults incantation is to configure a specific setting. For that tool, you’ll need the foundation established in this and the previous defaults posts.