How to Wipe Your Mac and Install Yosemite the Right Way

By Christopher Phin on at

I used to have the rule that every time Apple launched a major new operating system, I’d do a clean install – wipe my hard disk, put a fresh system on it, laboriously reinstall my apps and copy my data back across. Even if not strictly necessary, this was a reasonable policy in the days when Apple’s release schedule was infrequent, and when each release made big under-the-hood changes.

However, the now-annual cycle allied to the robustness of the core OS and the upgrade-in-place process had meant that since around 10.7, I hadn’t done it. But with Apple's newly available Yosemite already acting up in small but significant ways on my trusty old 2008 MacBook Pro, and a lot of accumulated crud on its SSD, it was definitely due.

A clean install gives you a fresh, efficient system, so I decided to put myself through the hassle of doing one. Once I'd decided to do it, I was actually, if tragically, a little excited about it, so if you want to do the same, hare are a few things you should think about before you begin to make sure it’s as pain-free as possible.

Back Up Off Me!

Oh, sweet lord, back up. Back up in multiple ways to multiple places; you know this. For my money, if you’re about to do a clean install, you should do a bootable backup just for it – in addition to whatever other system you have. This is because you can put it to one side as a snapshot of your system just before you did the clean install, and jump back to it instantly by booting from the dedicated backup in case there’s something you didn’t anticipate. (Remember that while Intel Macs can boot from drives mounted over USB, PowerPC Macs need to boot over FireWire.)

I use SuperDuper! to do these bootable clones, but the venerable CarbonCopyCloner or even the Restore tab of Disk Utility will do just as well. Once you’ve backed up, boot from that backup (hold ⌥ during startup to pick it) and confirm it’s working and that everything’s present and correct.

Play System Detective

First get your Mac running as you would typically and then scrutinise it to look for things that you will need to recreate on your new, clean system and anticipate problems – scan along the Dock, in the menu bar, in the Services menu, and ogle what options you see when you right-click typical files in the Finder.

If you’re being really thorough, look in the list of running services in Activity Monitor, since some things will be running “headless” – in the background. You’re looking for things that need to be added to a clean system in order to make it work for you – but do also take this as an opportunity to ditch things you’re not really using, since this will mean a less bloated, more robust system.

Capture Your Current Setup

One of the most annoying things in cleaning down a system is that your old one had grown familiar and comfortable over the years, and if you’re anything like me, using a fresh one is a bit like breaking in new shoes – it’s all very smart, but a bit uncomfortable, like your Dock in the wrong order but you can’t remember what the right order is.

One way you could combat this is to identify and copy across loads of preference files, but I prefer to do it more old school: taking a screenshot of my current system showing everything in place. Mine’s pictured above, which shows the Finder sidebar as well as the Dock and menus. You might need to capture different stuff, and remember that some apps let you export out the settings for your workspaces.

Oh, and it should go without saying to make sure you copy this information off the Mac before you wipe it. Not that I’ve done similar in the past, you understand…

Save Out Settings (Well, the Important Ones)

iCloud and syncing in general can help with some of this these days, but it’s still worth thinking if you use apps that need particular data exporting out ahead of time. For me, the two biggies are the settings for iStat Menus (the first app I install on any new Mac) and some custom Actions I have built in Photoshop. Save ’em out, stash ’em somewhere safe.

Source All Your Software

Before you wipe a Mac, make sure you can reinstall all the apps you need. If your apps are all from the Mac App Store, great, since reinstalling them is a case of clicking a few buttons on your new system. But for everything else, make sure you have install discs or access to downloads, as well as serial numbers, all to hand. I put disc images for big apps in a folder on my Drobo and store serials in Wallet.

It can actually be easy to forget what apps you had installed, so an easy way to remember is to go to Applications, ⌘A, ⌘C then ⌘V into a Plain Text document to quickly generate a list. (You might want to do the same for Utilities as well.) Again, though, don’t just unthinkingly reinstall everything – use this as an opportunity to ditch cruft.

Totally Deauthorised

Some things on your Mac get authorised to a server, and usually you get a limited number of activations. Before you wipe, deauthorise it for each, so that your old system isn’t using up one of your precious activations. For me, I deauthorise it to play my iTunes Store purchases and Audible audiobooks, not to mention Creative Suite.

The Start of a New System

Rightio, you’re probably ready to go. Start up from an installer drive (see Dan Frakes’ handy guide on how to create a bootable Yosemite installer) then go to Disk Utility before you install to erase your internal hard disk or SSD. Install, then step through the process of creating a new account.

Once you’re logged in, there’s one more thing I would do before copying back data, reinstalling apps or linking your new system to, say, cloud backup services: rename it. Go to System Preferences → Sharing and then change the Computer Name to something new; this means it will be very clear which machine originated files in any sync system, and should reduce the potential for conflicts.

Now: slowly, carefully, copy over your old data from the backup, and reinstall just what you want and need – and enjoy your fresh, nimble new system! If you’ve forgotten anything, just reach for your backup. After all, that’s what it’s for.

Christopher Phin was formerly editor-in-chief of Mac Format and Mac Life, and has been writing about tech since the start of the millennium, which sounds much more impressive than it probably is. You can read him here or follow him here.