What 'clean install' means
Also would like to update to Lion, but am afraid to do so. Doing an update is self explanatory I guess, but what is meant by a 'clean install'? What do I have to do then?
Hi Mary,
"Clean install" means reformatting your Mac's hard drive and installing Lion on it, as if it were a brand new machine and your previous OS was never there. That sounds drastic (and it is), but it doesn't have to mean starting over on all your applications and files. If you did a Time Machine backup just before, you can then use the 'Migration Assistant' feature to bring back your applications, files, and preferences. Any application that followed the Mac guidelines for where to put things should transfer pretty smoothly.
Power users often favor clean installs because we get uptight about the 'purity' of our systems. Laying Lion on top of Snow Leopard almost certainly means some things will be in a hybrid state, and files or settings that were only relevant to Snow Leopard
might still hang around as cruft. We're not sure what's different, but we
believe that starting fresh might make for a smaller install, a slightly faster one, or clear out any old glitches that have accumulated. It's like spring cleaning.
Is it necessary? No. Apple's in-place upgrades almost always work fine. And I suspect most of us would be hard-pressed to point out a clear, practical difference in the average case. There are exceptions; if your system has been working poorly, for instance, a clean install might be a more reliable way to clear out whatever went wrong.(*) But if you're generally satisfied, and you don't spend much time thinking about the internals of your system, trusting Apple and letting the upgrade perform itself is just as likely to leave you satisfied as doing things the "complicated" way.
(*)
E.g.: I already upgraded in place, but am considering a clean install because I'm still seeing an occasional "hard freeze" problem that I was having lately in Snow Leopard. I suspect some third-party app, maybe Skype or RescueTime or something, but since I don't know which one, taking off and nuking the place from orbit seems like the best way to be sure. Also, I'm a power user and therefore uptight.