Following yesterday’s announcements, OS X El Capitan 10.11.4 and OS X Server 5.1 are available on the Mac App Store and the update is highly recommended.

But, be careful, the two updates depend on each other. This may lead you to a network issue during the update process.

Indeed, OS X Server 5.0.15 can’t work on 10.11.4, only 5.1 can. And in the same time, OS X Server 5.1 require El Capitan 10.11.4, it can’t be installed on a previous version.

This mean you must update your system then your OS X Server. But if you use OS X Server you must certainly use the DNS service, so all your network — server included — should use only your internal DNS server. After the 10.11.4 update, OS X Server 5.0.15 won’t be able to start and your DNS service will be down.

This mean your update process must be this one:

  1. update your base OS in 10.11.4 (and if you’re still on 10.10, you must do the big jump);
  2. after the system update, change your network settings to use a temporary external DNS server;
  3. download the OS X Server update from the Mac App Store;
  4. run OS X Server and follow the assistant to finish the update;
  5. change again your network settings to get back to your regular settings.

This game with the DNS isn’t necessary in two cases:

  • you don’t use the DNS service built-in OS X Server (this means you use another internal DNS service or you OS X Server setup is wrong);
  • you’ve a secondary DNS service hosted by another OS X Server in your network and you do the updates sequentially.