If you’ve tried to upgrade Tiger server to Leopard, you’ve probably already learned that it’s a bumpy road. The process is so fraught with bugs that Apple themselves recommend against it in their Server Essentials manual, stating it should never be preformed on “production” machines. Unfortunately, not every organization has a spare XServe to experiment on, and those sharing files off internal disks may not want the hours of data shuffling that installing from scratch would entail.

The issues inherit in a Leopard Server upgrade can be addressed quickly and easily if you know what to look for. With a little advance preparation, and this article as a checklist, you can make sure the process is safe and successful for most OS X installations.

You’ll want to have checked in advance that any third-party applications you need run on Leopard, and you’ll definitely need a known-good backup in case something goes awry. Now let’s get started.

Document Server Settings:

The big problem with the Leopard upgrade isn’t that it loses data. In fact, it’s the opposite, with the newly upgraded volume turning on new services, adding duplicate users, or even sharing out random (and sometimes private) directories. The most important part of the process, then, is to document all your Server Admin settings prior to upgrade. You’ll want to have notes (or screenshots) detailing all your DNS zones, web sites, firewall configuration, etc. If your team doesn’t already document all their server settings in a change log, now’s the time to catch up on the paperwork.

Archive Open Directory:

The next step you’ll want to take is to export all your Open Directory settings. This includes not just your users and groups, their passwords, their managed preferences, but also all your Kerberos and Password Server data. After you’ve upgraded your server, you’ll restore this information to insure nothing’s been corrupted in the upgrade process.

You can do this easily by using the “Archive” pane in the “Open Directory” options of Server Admin. Simply click the “Choose…” button to set the location the collected data should be saved to, then click the “Archive…” button to set the name and password for the disk image that’s created. Type very carefully, and since the password isn’t verified before the image is created, test that you can open it before you proceed.

Install Leopard Server:

With your preparations made, you can run the Leopard Server install normally. You’ll be asked to enter your new Leopard serial number, but otherwise the process shouldn’t require any configuration. The upgrade takes about a half hour on the current generation of XServe, and you can fill the time by downloading any recent updates you plan on installing. When your server reboots, it’ll likely have a host of services you don’t want turned on, so it’s best to restart it with the network cable unplugged.

Reconfigure Services:

If all went well (or at least as expected), you should now have a fully functional Leopard Server. Maybe a little too functional, even. Leopard tends to turn on a bunch of undesired services during the upgrade process. Was your XServe an email or NFS server previously? There’s a good chance it might be now.

Open Server Admin, and select the your local machine from the left column. Now take a good, hard look at the services listed below it. Turn off the services you weren’t running prior to upgrade, then check your remaining service settings to make sure nothing unexpected has been added or changed. If you don’t need Apache 1.3, it’s a good time to upgrade to version 2.2 in the Web options as well. Now it’s time to plug back in the network cable and wrap up the job.

Restore Open Directory:

Now that the rest of the damage has been undone, you’ll want to clean up your account information. If your server remained an OD master through this process, you’re in luck. Otherwise, you’ll need to promote it in the “Settings” pane of the Open Directory options, then return to the “Archive” pane.

Choose the archive disk image you made earlier, and click “Restore…” to return your Open Directory domain to it’s pre-upgrade state. Once you’ve confirmed Open Directory accounts work locally, test each of the services you’re offering over the network as well, making sure that everything functions as it did prior to the upgrade process.

And voila! While not exactly fast or automatic, you should now have a newly upgraded and properly functioning Leopard Server. Now you can go find out what’s going to break when you upgrade your client machines…

Recommended Reading: While it may contradict some real-world experience, Apple nonetheless publishes an excellent guide on Upgrading and Migrating 10.5, essential reading for anyone planning a complex upgrade to Leopard Server.