How to Create a Bootable OS X USB Key

With OS X Mavericks and Yosemite, you can create a bootable OS X installer which can be used to install the operating system while started from removable media, such as a USB flash drive.

Before you’re able to create a bootable OS X installer, you’ll need to do the following first:

  1. Download the OS X Installer app from the Mac App Store.
  2. Mount the volume you want to convert into a bootable installer. This could be removable media such as a USB flash drive, or a secondary internal partition.
  3. You can then use the createinstallmedia tool to convert the volume from step two into a bootable installer based off the installer app from step one. To learn how to use createinstallmedia, use the following command in Terminal:

    OS X Yosemite

    /Applications/Install\ OS\ X\ Yosemite.app/Contents/Resources/createinstallmedia

    OS X Mavericks

    /Applications/Install\ OS\ X\ Mavericks.app/Contents/Resources/createinstallmedia

Examples

For example, assuming you have a volume mounted at /Volumes/SANDISK64GB and the OS X installer app is at /Applications/Install\ OS\ X\ Mavericks.app you could erase /Volumes/SANDISK64GB and convert it into a bootable installer with this command:

OS X Yosemite

sudo /Applications/Install\ OS\ X\ Yosemite.app/Contents/Resources/createinstallmedia --volume /Volumes/SANDISK64GB --applicationpath /Applications/Install\ OS\ X\ Yosemite.app

OS X Mavericks

sudo /Applications/Install\ OS\ X\ Mavericks.app/Contents/Resources/createinstallmedia --volume /Volumes/SANDISK64GB --applicationpath /Applications/Install\ OS\ X\ Mavericks.app

Example Output From Terminal Below

MacbookPro:~ user$ sudo /Applications/Install\ OS\ X\ Yosemite.app/Contents/Resources/createinstallmedia –volume /Volumes/SANDISK64GB –applicationpath /Applications/Install\ OS\ X\ Yosemite.app

Password:

Ready to start.

To continue we need to erase the disk at /Volumes/SANDISK64GB.

If you wish to continue type (Y) then press return: Y

Erasing Disk: 0%… 10%… 20%… 30%…100%…

Copying installer files to disk…

Copy complete.

Making disk bootable…

Copying boot files…

Copy complete.

Done.

MacbookPro:~ user$

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