Originally two separate services in Mac OS X Server, for Software Updates and later Content, it reached client versions of macOS in High Sierra in 2017.
OS X Server
A/UX was released for the Mac II in 1988, then in 1993 Apple changed course with a series of servers, before Mac OS X Server in 1999 and its first Xserves in 2002.
An extended tutorial-review of Mountain Lion Server, OS X Server 2.2, written in 2012-13, with copious screenshots.
A replacement for the NetInfo service in NeXTSTEP and early Mac OS X, Open Directory is an LDAPv3 service delivered as Directory Services, and essential to permissions, authentication and more.
The first version of its predecessor, NetInfo, also handled DNS lookups. When they failed, users found they were locked out of everything else. This has improved!
Content Caching server originated in 2005, as a feature in Mac OS X Server, which sold Xserves. Time Machine came in 2007, to support Time Capsules. Those legacies are so different, though.
Apple says that macOS Server is changing, then warns that almost all its services will be removed. After 19 years, is this the end?
Most apps and other software components in Sierra were updated, from the App Store to XProtect. Here’s a more complete list.
For the last 15 weeks, this iMac has been freezing sporadically. I have run out of ideas, and hope that 10.11.6 fixes the bug.
It’s not quite as simple as dragging the Server app to the Trash. Here’s how to get rid of Server properly.
The Eclectic Light Company 