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Installation
Thanks to planning by Apple, the installation process for the server software is trivial. You need to make sure that your new servers are already in the DNS for directory servicesparticularly Kerberosto install properly. I made the mail server an Open Directory master and the file server an Open Directory slave. The slave uses the master for authentication, so you need to maintain only one list of users and groups.
The install process went off without a problem on all three computers.