Creating a Mac OS X emergency boot disk is a great idea for any person who regularly repairs Apple Mac computers. How to create a Mac OS X boot disk is a complicated process, but this step-by-step guide to turning a USB Flash drive into Mac installation disk will give you the confidence you need.

If you have a spare USB Flash drive, you should turn it create a bootable Mac OS X installer. This Mac OS X Flash drive can be used to install Mac OS X efficiently, even on a Mac without an internet connection. The Mac OS X USB installer repairs the Mac’s hard drive in the case of emergency. It’s also incredibly useful if you need to fix and install Mac OS X Mavericks on multiple Macs (because you don’t have to download each installation from the App Store).

This guide enables you turn a spare USB flash drive into a bootable Mac OS X Mavericks installer. Follow these steps to create your emergency Mac OS X boot drive.

You will need the following:

  • USB Flash Drive (8GB or larger). Note: it is erased during this procedure.
  • Install OS X Mavericks file (from Mac App Store)
  • Mac OS X 10.6.8 or greater

See also:

Step 1: Download Mac OS X

Open the App Store and search for Mac OS X Mavericks. Now click on Download (or Free and Install if you haven’t already installed it). If you want to install an older version of the operating system, you need to already have the installation file, which is found in Applications and is called “Install Mac OS X Mountain Lion” or similar. But we advise you to use the latest version of Mac OS X from the App STore.

Note that when the Install OS X Mavericks file has finished downloading, it launches the Mac OS X Installer. Click on Install OS X and Quit Install OS X to close it.

Create an emergency boot drive - Step 1

Step 2: Prepare the USB drive

Attach the USB Flash drive to your Mac and open Disk Utility (found in Applications > Utilities). Select the disk in the Sidebar (the root disk not a Volume contained on it). Now click on Partition and change Current to 1 Partition. Click on Format and change it to Mac OS Extended (Journaled). You should change the name to something recognisable like Mac OS X 10.9 Installer.

Create an emergency boot drive - Step 2

Step 3: Setup GUID

Click on Options in Disk Utility and choose GUID Partition Table. A GUID Partition Table enables the volume to Start Up an Intel-based Mac. Click on OK. Click on Apply and Partition to wipe the disk.

Note: This removes everything on the USB Flash drive.

Create an emergency boot drive - Step 3

Step 4: Access hidden files

Open the Terminal app inside the Utilities folder. Now cut and paste this command into Terminal and press return.


defaults write AppleShowAllFiles 1 && killall Finder


The Finder refreshes, and now displays all hidden files.

Create an emergency boot drive - Step 4

Step 5: Open Mavericks file

Locate the Install Mac OS X file in the Applications folder. Right-click it (Command-click) and choose Show Package Contents. Open the Contents folder and SharedSupport folder and double click the InstallESD.dmg to mount the OS X Install ESD folder in the Finder.

Create an emergency boot drive - Step 5

Step 6: Base system

Double click the Install ESD folder and locate the BaseSystem.dmg folder (it should be in a light grey to signify that it is a hidden folder). Return to Disk Utility and Drag the Basesystem.dmg from the Finder to the Source field in Disk Utility. Now drag the Mac OS X 10.9 Installer volume from the Sidebar to the Destination field in Disk Utility.

Create an emergency boot drive - Step 6

Step 7: Click on Restore.

Now click on Restore and Erase. The installation process takes around 20 minutes depending on the speed of your system.

Create an emergency boot drive - Step 7

Step 8: Delete the Packages alias

Once the files have copied over, the Install Mac OS X 10.9 drive should mount automatically. Open the install Mac OS X 10.9 volume and navigate to System, Installation delete the alias file to the Packages.

Create an emergency boot drive - Step 8

Step 9: Copy Packages folder

Now return to the OS X Install ESD folder and drag the Packages folder to the System / Installation folder on the Install Mac OS X 10.9 volume you’ve just created. Drop the Packages folder into the same place (System / Installation) where you just deleted the Packages Alias.

Create an emergency boot drive - Step 9

Step 10: Turn on hidden files

The final thing you should do is make sure your files are hidden again in Mac OS X. Copy and paste this command back in Terminal.


defaults write AppleShowAllFiles 0 && killall Finder


The Finder should flash and all hidden files should be removed from view.

Create an emergency boot drive - Step 10

That’s it. You now have a fully working, bootable flash drive that can be used to boot and install Mac OS X 10.9 on any Mac. It can be used to install Mac OS X even without an Internet connection. Just insert the USB Flash drive into a Mac and hold down the Alt key while booting up. Select the drive to boot from it and follow the Install Mac OS X instructions.