As a modern operating system, macOS is supporting features for central network management. An administrator can setup a network server in a way that all client computers automatically load predefined settings from the central server. This can save a lot of work and simplify management enormously. Imagine a campus network of a large university which has bought 50 new Macs for a computer room which should be used by students. It would be tedious work to configure all the basic preferences 50 times when setting up the new computers, for example the name of the university’s e-mail server as default value for Apple’s Mail program. Instead, the network administrator can define such an important preference setting on the master management server once and then force all new Macs to automatically read this setting and enable it when they connect to the network.
Mac OS X originally used the term Managed Clients to refer to this feature. It is usually abbreviated as MCX (“Managed Clients for Mac OS X”).
The application used to setup predefined network preferences was the Workgroup Manager which has been an optional part of Mac OS X Server. A managed preference setting could either be defined to be loaded once by the clients, or to be enforced “always”. In the first case, the setting will have the character of a suggested default. The MCX technology here just helps to setup a new network computer, preloading it with configuration information and in-house standards it should “know” about. Users are free to overwrite the preferences later if they like to do so. In the latter case, the preference setting will have the character of an enforced policy. For example, if the students should not be allowed to burn CDs with the Finder in the aforementioned campus example, macOS can ensure that the preference setting which enables the burn features of the Finder is always kept at a “no” value.
In the meanwhile, the MCX technology has been superseded by Mobile Device Management (MDM) as of Mac OS X 10.7 Lion and later. It is implemented by Apple’s Profile Manager application which is part of macOS Server. MDM works by remotely installing reconfiguration commands on clients. These command sets are called Profiles. For PrefEdit, it doesn’t matter which technology is used to manage default settings in the network. In both cases, the affected setting is labelled as Managed.
It is beyond the scope of this manual to describe how MCX or MDM technologies work. It is only important to understand that some specific preference settings can be automatically readjusted by macOS at certain points in time, for example when starting a new computer, or each time a user logs in. The fact that a setting is being managed does not become visible in a preference file. However, PrefEdit will display this aspect when opening a domain of the preference database. In this case, a check mark in the column Managed will appear for each managed setting.