A nice feature of recent OS X versions is OS X Recovery. If you ever have system or drive issues, OS X Recovery lets you boot your Mac into a special recovery mode to check or repair your hard drive, browse the Web for troubleshooting help, restore your drive from a backup, or even reinstall OS X itself. (See our hands-on with Mountain Lion Recovery for all the details.)
OS X Recovery is a convenient feature that, in theory, means you no longer need an OS X Install disc or a bootable external hard drive with the OS X installer. But there are still good reasons to have one. For example, if you want to install Mavericks (OS X 10.9) on multiple Macs, a bootable installer drive is faster and more convenient than downloading or copying the entire OS X installer to each computer.
But even for troubleshooting, a bootable installer drive has advantages over OS X Recovery. For starters, OS X Recovery doesn’t include the full Mavericks installer—it requires you to download over 5GB of data before you can reinstall OS X 10.9—whereas a bootable installer drive contains all the necessary data, making installation much, much faster. And if you’ve got a Mac that doesn’t support OS X Internet Recovery—a variation of OS X Recovery that loads over the Internet and requires special firmware—recovery mode may not even be available if your Mac’s drive itself is having problems. (OS X Internet Recovery is available on mid-2011-or-later Macs, as well as some older Macs that have received relevant firmware updates.) A bootable installer drive, on the other hand, will always be there for you.
The problem for newer Macs
If you purchased OS X 10.9 from the Mac App Store, creating a bootable Mavericks installer drive from the Mac App Store version of Mavericks is relatively simple. However, if you have a Mac that debuted after Mavericks was released in October 2013, your Mac shipped with Mavericks pre-installed, so you don’t have an easily downloadable version of the installer—unless you happened to purchase Mavericks for another, older Mac. This means you can’t use our standard tutorial.
Fortunately, it’s possible to create a bootable Mavericks installer drive even if your only Mac is a model that shipped with Mavericks—although doing so requires a bit more work than if you had purchased the Mac App Store version.
IMPORTANT: To reiterate, if you’ve downloaded Mavericks from the Mac App Store (for any other Mac you own), so you’re able to download the Mac App Store version of the Mavericks installer, you don’t need to use the procedure in this article. You can instead use our standard instructions for creating a bootable Mavericks installer drive. As long as you download the latest version of the Mavericks installer from the Mac App Store—instructions are provided in that tutorial—you’ll have a bootable Mavericks installer that should work with every Mavericks-compatible Mac.
The solution for newer Macs
When you use OS X Internet Recovery to reinstall Mavericks, your Mac contacts Apple’s servers, identifies itself, and requests the appropriate Mavericks-installer data. Apple’s servers verify the Mac model and then, assuming it’s a Mac compatible with OS X Internet Recovery, provide the roughly 5GB of installer data for download. Once that data has been downloaded, OS X Recovery restarts your Mac, immediately installs the OS, and then deletes the installer data.
The trick you need to perform is to interrupt that process—safely—so that you can grab the installer data and keep it. Here are the steps to take:
Boot into recovery mode by holding down Command+R at startup; you’ll eventually see an OS X Utilities window.
Connect a drive—a hard drive, a thumb drive, or the like—with at least 12GB of free space. (The drive must be formatted as Mac OS Extended [Journaled], and must have a GUID Partition Table. Follow these instructions to properly format the drive, if necessary.)
In the OS X Utilities window, select Reinstall OS X and then click Continue.
On the OS X Mavericks screen, click Continue. You’ll see the message, “To download and restore OS X, your computer’s eligibility will be verified with Apple.” Click Continue, then click Agree (twice) on the next screen to agree to the license agreement.
Select the drive onto which you want to “install” Mavericks. The important thing here is to select your external drive, not your Mac’s drive.
Click Install to begin the download. Depending on your Internet connection, the download can take anywhere from under an hour to several hours (or even, if you’re unfortunate enough to be on a very slow connection, considerably longer).
IMPORTANT: Monitor the download’s progress. As the progress bar gets near the end, get ready, because once the status reads About 0 seconds remaining, the progress bar will disappear, the screen will turn gray, the installer will spend a minute or two cleaning up, and then your Mac will restart. As soon as the screen goes black—meaning the Mac is restarting—unplug your external drive. If you wait too long, your Mac will boot into the OS X installer on the external drive, starting the installation process. Interrupting that process can leave your Mac unable to install OS X unless you restart it and zap PRAM.
Once your Mac has booted from its normal startup volume, reconnect the external drive. Alternatively, you can connect the drive to another Mac and proceed with the remaining steps using that Mac.
Open the external drive, and you’ll find a folder called OS X Install Data. Open this folder to view its contents. The important file is the one called InstallESD.dmg, roughly 5.3GB in size. (If the OS X Install Data folder has a “no access” icon, select the external drive in the Finder, choose File > Get Info, and expand the Sharing & Permissions folder in the Info window. Click the padlock icon at the bottom of the window, provide an admin-level username and password, and then click the box next to Ignore Ownership On This Volume.)
If you plan to use the same hard drive for your bootable installer drive that you used to download the installer, you’ll need to copy the InstallESD.dmg disk image to your Mac’s internal drive, or another drive, before proceeding. Use that copy of InstallESD.dmg in the next set of instructions, below.
Now you’ve got the latest Mavericks-installer data, and you’re ready to use that data to create a bootable installer drive or disc. Here are the steps required:
Double-click the InstallESD.dmg disk image (in /OS X Install Data on your external drive) to mount its volume. That volume will appear in the Finder as OS X Install ESD.
The file you want to get to is actually another disk image inside OS X Install ESD called BaseSystem.dmg. Unfortunately, BaseSystem.dmg is invisible, and because this is a read-only volume, you can’t make BaseSystem.dmg visible. Instead, you’ll mount it using Terminal, which makes it visible in Disk Utility. Open the Terminal app (in /Application/Utilities), and then type open /Volumes/OS X Install ESD/BaseSystem.dmg and press Return.
Launch Disk Utility (in /Applications/Utilities). You’ll see both InstallESD.dmg (with its mounted volume, OS X Install ESD, below it) and BaseSystem.dmg (with its mounted volume, OS X Base System, below it) in the volumes list on the left.
Select BaseSystem.dmg (not OS X Base System) in Disk Utility’s sidebar, and then click the Restore button in the main part of the window.
Drag the BaseSystem.dmg icon into the Source field on the right (if it isn’t already there).
Connect to your Mac the properly formatted hard drive or flash drive you want to use for your bootable Mavericks installer.
In Disk Utility, find this destination drive in the left sidebar. You may see a couple partitions under the drive: one named EFI and another with the name you see for the drive in the Finder. Drag the latter—the one with the drive name—into the Destination field on the right. (If the destination drive has additional partitions, just drag the partition you want to use as your bootable installer volume.)
Warning: This step will erase the destination drive or partition, so make sure it doesn’t contain any valuable data. Click Restore, and then click Erase in the dialog box that appears; if prompted, enter an admin-level username and password.
Wait for the restore procedure to finish, which should take five to ten minutes.
In Disk Utility, select BaseSystem.dmg (not OS X Base System) on the left, and then click the Eject button in the toolbar. This action unmounts the disk image named OS X Base System. (If you don’t do this, you have two mounted volumes named OS X Base System—the mounted disk image and your destination drive—which makes the next step more confusing.)
Open the destination drive—the one you’re using for your bootable install drive, which has been renamed OS X Base System. Inside that drive, open the System folder, and then open the Installation folder. You’ll see an alias called Packages. Delete that alias by dragging it to the Trash.
Open the mounted OS X Install ESD volume, and you’ll see only a folder called Packages. Drag that folder into the Installation folder on your destination drive. (You’re basically replacing the deleted Packages alias with this Packages folder.) The folder is about 4.8GB in size, so the copy will take a bit of time, especially if you’re copying to a slow thumb drive.
Eject the OS X Install ESD volume.
If you like, you can rename your bootable installer drive from OS X Base System to something more descriptive, such as Mavericks Installer.
Though you created your bootable installer drive from a particular Mac, you can boot almost any Mavericks-compatible model from this drive and install Mavericks. You can also use any of the Mavericks installer’s recovery and restore features from the installer’s Utilities menu. I say “almost” because when Apple releases even newer Mac models, those models will come pre-installed with a newer version of Mavericks, so the installer drive you just created won’t immediately work with them. Until Apple updates the downloadable Mavericks installer to again be universal—something the company does silently, so you never know when it happens—you’ll need to create a new Mavericks installer drive using one of those Macs.