Mac Maintenance: An OS X Reinstall Checklist


It was the stuff of nightmares: What I expected to be a routine repartition of my hard drive for Boot Camp became a 12-hour slog of a reinstall. My pain can be your gain, though. It’s a good idea to reinstall OS X (s aapl) every once and a while to keep your system running smoothly, so here are a few things to keep in mind before you begin. While most are pretty obvious, the list might prevent one or two head-smacking moments of regret.

Time Is Not On Your Side

Assuming your reinstall isn’t an emergency from a hard drive failure, make sure you have plenty of time to devote to this task. As I often joke with a friend, do not anger or tempt the Data Gods. When’s a great time to do the reinstall? On a day you have the house to yourself, and nothing else to do. When’s a horrid time to decide to do this? When you’re on deadline, late on a project, or rushed. Because when there’s little time for anything to go wrong, everything will go wrong. Depending on how much data you have, a backup, reinstall, and data restore can take you about eight hours to complete. Don’t try it if you only have four, or decide you can “deal with stuff later.” It’s never that simple.

Your Backup Is Not Good Enough

Time Machine is a fantastic feature. It’s perfect for those “oops, I deleted that file” moments, but when you’re reformatting your drive, do not place your faith in Time Machine alone. I’ve run into a few problems restoring from it (it once told me there was “one minute remaining” for around 12 hours).  External hard drives are cheap. Buy a 1TB drive and manually backup your data. What data should you be sure to backup?

Your User Folder: Music, Downloads, Documents, Pictures, etc. Don’t forget to de-authorize your iTunes account (otherwise your prior install will count towards your maximum of five machines you can authorize). Make sure you’ve got your mobile apps backed up (they’re in the iTunes folder, so if you grab that folder, you should be ok). You don’t want to lose any apps you’ve downloaded that have since been removed from the App Store (like VLC, for instance).

Applications: You don’t need to grab the whole folder, but make sure you copy your favorite apps to save time, and in case you can’t find the original install media. Grabbing Application bundles and folders will also save you the time-consuming process of re-patching software after a reinstall.

Application Support and Preferences Folders: In your ~\Library folder are two important folders to backup: Application Support and Preferences. While you can troll through them and grab what you think you need, I recommend just backing up both directories in their entirety. In these folders are any preferences or extra files an App needs. For instance, your custom templates for Pages are in \Application Support\iWork\Pages. OmniGraffle’s Stencils are also in its own Application Support folder. Preferences you may not need to grab anything from, but it’s good to make sure you’ve got a copy if an app writes data to it.

Fonts: If you use a lot of custom fonts, like I do, you might also take for granted they’re always there and overlook them. Make sure you back up that folder, too.

Preflight Checklist

Ok, now you’re sure you’ve got all your data backed up, so what else do you need before nuking your OS and starting from scratch?

Install Media and Serial Numbers: I keep all my serial numbers in the cloud on Google Docs and Evernote. Make sure you have the install media (be they discs or .dmg files) for apps like Microsoft Office, and that you have all your serial numbers in a safe place in the cloud or in hard copy.

Your Wireless Password: Remembering this can be like trying to find your birth certificate when you really need it. You’re sure it’s here, someplace, right? Make sure you can remember it, or reset it now (and write it down) while you’re still on the network.

Your Assorted Online Accounts: My bank account username is always a gotcha for me. Go through sites you access a lot and make sure you’ve got the usernames and passwords handy, since your browser cookies won’t be around to help your deficient memory post-reinstall.

Your Backups: Sure, I’ve gone into it at great length, but now’s the time to triple check you’ve backed everything up.

Good luck! Hopefully, this advice will save you a little frustration whenever you happen to reinstall OS X. Anything I’m missing? Let us know in the comments.

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All of these steps apply to a Windows reinstall as well, or any other OS.

Ideally, you would have everything backed up on a regular basis so you wouldn’t have to back up right before a reinstall. But my systems not ideal. I definitely do not backup enough.

Of the time you alloted, how much if it is actually used by OS X install?

Mark Crump

For JUST the OS X install, counting patches, about 1.5 hours, depending on your internet connection and if you downloaded the combo update already. Just the install is 30-40 min, I think.


You actually do not need to de-authorize your iTunes account. iTunes looks at the MAC address of the computer when it authorizes it, and seeing that you’d only have a different MAC address in the event of a logic board replacement, or a new machine entirely, this is an unnecessary step when simply preparing to Reinstall the OS. If for some reason you did need to reauthorize the computer, iTunes would notify you that it has already been authorized.

Mark Crump

I just did a reinstall (and, naturally, forgot to deauth), and when I played protected content for the first time, it prompted me for a reauth.


In our hosehold, we have a late 2006 iMac which came with Tiger. I upgraded it both to Leopard and Snow Leopard when those came out. I haven’t had to reinstall it a single time (Snow had to be fixed once when stupid Flash crashed it at an unfortunate moment, but that wasn’t a clean reinstall, just restoration of system files or something), and the Mac runs just fine. Mac OS is not Windows that needs to be reinstalled every year (unless the only apps you ever installed on your Windows PC are the Microsoft Office programs). In my humble opinion, if it ain’t broke, don’t fix it. Your Mac runs great – don’t reinstall it. Your Mac has issues – repair the install. Your Mac is, like, totally messed up – backup everything (Time Machine is your friend!) and reinstall.


This post couldnt have come at a better time! I’ve been wanting to reinstall, but I got my MacBook off eBay without the Reinstall DVDs… I know, fail on my part. Does anyone know if there is a way to download the DVD from apple somehow? Or some other way to get it? And can I use any snow leopard DVD to reinstall? Like, could I borrow my buddies disc? Thanks for the post!


Unfortunately, you can only reinstall with a disk from the same model (at least I’m pretty sure). I know for sure that you can’t use iMac disks to reinstall on a MacBook. I’ve tried. But you might be able to use any MacBook disks for any MacBook. Don’t quote me on that though.

Mark Crump

You can use any Snow Leopard retail disk on any Intel-based Mac, however the install media that came with your Mac can only be used with that model Mac. In other words, my mid-2009 MacBook Pro discs can only be used with a mid-2009 MacBook Pro.

The Snow Leopard retail disk is only $30, so it’s worth grabbing it to have your own disc.

Speaker to Wolves

Do NOT listen to this man. (Just the fact that it took him 12 hours to do a Bootcamp install should give you a clue that he hasn’t the faintest idea what he’s talking about.)

It is not “good idea to reinstall OS X every once and a while” and if you have to reinstall your OS periodically to avoid issues, you’re doing something wrong. Over the years I have upgraded my Mac OS X 5 times, migrating from a G5 Mac Pro to a Quad Core Intel along the way without ever once having to reinstall an OS. And I’m running Bootcamp without ever to repartition my boot drive.

Seriously, the proper care and feeding of the Mac OS does NOT entail reinstalls “once and awhile.”

Mark Crump

The 12 hour Bootcamp install was a comedy of errors involving a bad memory and a license key issue with Windows 7. To make a long story short, the license I have for Win 7 was an upgrade license from XP, and I forgot that. Also, I ran into the dreaded “cannot move files” error when I wanted to resize the Win7 paritition — basically, when I blew away the old partition, OS X couldn’t create a larger partition.

I think backing up your stuff – be it photos, music or other files is quite underrated. There’s nothing worse than losing valuable files and realizing you didn’t have them backed up somewhere. I ran a series of articles about these situations ( which will hopefully help somebody avoid that scenario.


I use 1Password for all my passwords and software licenses. The software is available through their website anytime and my 1P info is kept in Dropbox. Between Dropbox, Evernote and 1Password, the last time my computer went down, I switched to my partner’s Mac while repairs happened and barely missed a beat.


External hard drives are cheap. Buy a 1TB drive and manually backup your data. What data should you be sure to backup?

Ehhhh… or you could just let SuperDuper take care of this for you.

I let SuperDuper do a nightly backup while I’m sleeping, and I let Time Machine do its ~hourly thing, so if my computer ever craps out completely, I can plug in my external drive to any other Mac, boot from the SuperDuper partition (bringing me up to that morning at 4 am), restore from the Time Machine partition (bringing me up to one hour ago) and I’m good to go.


I just reinstalled last night. I made a flash drive with all the application install files on it, as well as a time machine back up, and a secondary bootable backup, incase I wasn’t able to finish before work the next day.

It worked very well, was able to go back in under 1 hour (minus the time it took to transfer data while I slept)

Cold Water

Why routers don’t just have a space to write down critical information like keys and passwords, I’ll never know. Until then, you should just sticker that information on the bottom or something.

Physical access trumps any security on a system, and not like your wireless key has to be some deep, dark, personal secret anyway.

Moritz Schmale

I also backup my Library Folder to keep all my favourite settings. This will also keep your Keychain (which stores the online-passwords as well as the Wireless password).

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