Apple has announced that with the release of Mac OS X 10.7 Lion, the operating system will be available only via download from the Mac App Store. Past versions of the Mac OS X operating system have always been available for purchase on a bootable DVD and with some systems like the MacBook Air, they’ve been included on a bootable USB drive. To create your own bootable USB device using your own flash drive (note that the device must be at least 4GB or larger), follow the instructions below.

1) Purchase and download Lion from the Mac App Store on any Lion compatible Mac running Snow Leopard.


2) Right click on “Mac OS X Lion” installer and choose the option to “Show Package Contents”

Show Package Contents


3) Inside the Contents folder, you will find a SharedSupport folder and inside the SharedSupport folder you will find the InstallESD.dmg. This is the 10.7 Lion boot disc image.



4) Copy InstallESD.dmg to another folder like the Desktop.  To do so, simply click and drag the file to the desired location while holding down the Option key.


5) Plug in the flash drive and launch Disk Utility (/Applications/Utilities).


6) Make sure the flash drive is properly formatted highlighting the flash drive at the left (make sure to select the device and not the volume shown under it) and clicking the Erase tab across the top right.  Then ensure that the Format drop-down menu is set to Mac OS Extended (Journaled) and click the Erase button.  Confirm the dialog ensuring that you want to erase the device and all information on it (make sure you backup any existing information on the flash drive before this point).

Disk Utility Formatting


7) Select the Partition tab on the top right.

Creating Lion Installer Partition

Using the drop-down menu for Volume Scheme, choose 1 Partition as the partition scheme.

Choosing Number Of Partitions

Highlight the partition by clicking on it in the space it is shown below the Volume Scheme drop-down and then click on Options underneath it.  Select GUID Partition Table and click OK. This will allow the Mac boot from the drive.

GUID Partition Table

You may now name the device in the Name textbox. Insure that Format is set to Mac OS X Extended (Journaled). When you have finished, click the Apply button to format the USB device.  A warning will pop-up asking if you are sure you want to partition the media.  Click the Partition button to continue.

Formatting The Flash Drive


9) Click on the newly created volume listed under the USB device on the left. This volume will have the name of the device you set in the previous step.  Click the Restore tab at the top right.  In the Source area click the Image… button. Select the disk image InstallESD.dmg and click open (you may also drag-and-drop the disk image into the Source area).

Restoring Image To Disk

In the Destination area, make sure that the USB device’s name is showing. If it isn’t, simply click and drag the volume from the list at the left into the destination area.  Click Restore and confirm the dialog informing you the volume will be erased.  You will be prompted to enter the admin password for your Mac and the process will begin.

Restoring Erase Contents Warning

The bootable USB device will be created and a progress bar will show the current status of the operation at the bottom of the screen.

Restoration Progress Bar


10 ) When the operation is complete, you can verify that the flash drive is now bootable by selecting it and clicking the Info button in the upper left corner of the Disk Utility window.  Bootable status will show as Yes.

Bootable Flash Drive Information


To boot from the USB device, simply hold down the Option key while your Mac is booting up. A screen will appear asking you which volume you would like to boot the system from. Click on the OS X installer USB drive and the system will boot using the USB stick. You will see faster boot speeds using the USB installer compared to a DVD installer disc.


  1. Chris Borland

    In step 6 of the process above, I accidentally formatted the flash drive I was using for my Lion installation flash drive as “Mac OS Extended” instead of “Mac OS Extended (Journaled) .”

    Is that okay?

    The flash drive seems to work, though I haven’t tried to use it to actually install Lion on a Mac (I tested the flash drive by plugging it into two different Macs, and going through all the steps up to but NOT including the actual Lion installation step).

    Would it be best to re-download Lion from the App store (can I do this without paying for it again?), find the InstallESD.dmg file, and start all over … this time correctly formatting the flash drive before beginning as “Mac OS Extended (Journaled)?”

    Please inform.

    Thank you.

    • Inc.

      Journaling is a technique that helps protect the integrity of the Mac OS Extended file systems on Mac OS X volumes. It both prevents a disk from getting into an inconsistent state and expedites disk repair. You should be fine without journaling on the flash drive since it won’t see a lot of use.

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