There are some things you can do prior to installing that I sometimes recommend. Many of these things are not guaranteed to work (and some people actually say will do more harm than good). I, for one, don’t see an issue with the basics that some recommend: Start by repairing permissions: either run Disk Utility from your hard disk while in OS X, or do so from the Tiger DVD. Make sure you are currently at Tiger 10.4.10 (as of this writing, 10.4.10 is the latest public version, with .11 on the way).
Like with any other OS upgrade, you’ll want to back up all of your data (duh). The trick I used for my system upgrades/moves previously, and with the Leopard beta, was to run an exact copy to a Firewire disk using SuperDuper. SuperDuper is nice because you can at least make an exact copy of your disk that works well in the demo mode. To get advanced features, you have to buy a license. SuperDuper will also take careful looks at system files, Spotlight info, etc., and is good about copying the correct data while leaving system-specific files behind.
I’m typing this on my new MacBook Pro, where I’ve used the Migration tool to safely move from my “backup” Firewire drive. Leopard continues the Migration Assistant, and even improves on it, so unless we hear reports that it no longer works, you can most likely safely migrate from a Firewire backup made with SuperDuper. This works well even when moving between PPC and Intel Macs. I mainly recommend this strategy, even though Leopard asks you to back up prior installing. The reason being, Leopard’s backup uses Time Machine, which right now, I’m not sure would work with pre-Leopard copies of OS X. If for some reason, you need to bail out, and are stuck on Tiger, this is the safest bet.
At this point, with your backup safely in your hand, and everything updated, you can go ahead and stick in the Leopard DVD, and follow the instructions to reboot and start the process. Here’s where you can vary:
1. Some folks say it’s okay to simply do an “upgrade” install over a previous version. Usually, Apple does a fairly good job at keeping their installs clean and stable (unlike a certain other OS maker – ahem). With Leopard, however, we’re seeing some major changes to core files, and the introduction of dozens of new frameworks, so this may be a case in which it’s wise to not do a straight upgrade.
2. The next option – if you didn’t use SuperDuper to make a good backup earlier – is to do the old-fashioned “Archive and Install”. I’ve used this in the past, and it’s actually very useful in recent versions of OS X, where you can use the Migration Assistant on your rebooted fresh install to copy the files you want back over from your old archived copy of OS X. Fair warning, though: you’re going to need enough free space (read: a huge hard drive) to handle a copy of all of the data currently on your drive.
3. If you already have a backup (courtesy of SuperDuper), you can do a clean install of OS X. This is also known as “Erase and Install”, and does as it says – it wipes your drive clean before loading a standard new install of the OS. It, like the archive and install option, will provide the Migration Assistant, so you can get all of your data back from the Firewire disk.
Sure, you can use a second hard drive in your Mac Pro, but everybody knows you’ve already filled that up with your illegal downloads of the last few seasons of “Lost” and “Star Trek: Voyager”, right? It’s okay, I won’t tell anyone.
The Easy Part: The actual install
After you select the type of install you want, you’ll be asked a few other easy-to-answer questions, and you’ll be guided through the rest of the process before it just copies the files. After that, you’ll restart the computer, and you may or may not need to run through the Migration Assistant before you can be on your merry way, enjoying your new copy of Leopard with all of your old stuff still intact.
Make an updated backup
Once you’re confident with your Leopard install, you can erase that Firewire drive, and activate Time Machine. Unfortunately, as I was writing this, MacRumors discovered that Apple may have pulled the feature allowing Time Machine backups to Airport hard disks. I guess we’re back to plugging in the drive the old-fashioned way.