How To Create a Bootable Mountain Lion (OS X 10.8) Installation DVD or USB Drive [Updated]

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As many people know, Apple’s new Operating System, OS 10.8 – a.k.a. “Mountain Lion,” is officially available for purchase and download. Just head over to the Apple App Store on your supported Mac and purchase and install Mountain Lion now! As part of the upgrade process, your Emergency Recovery Boot Partition will be upgraded to support re-installs of Mountain Lion without the need for an external installer. But what if you want to install Mountain Lion on another computer (that is supported)? There is a way to easily do this, but remember, you should only do this with computers that you own or manage (and you wouldn’t need to do this if you had all of your computers use your Apple ID in the App Store – you would just install right from there).


So, if you do want to create an installer DVD (and you could do this with a USB drive as well), here are the steps to do so.

NOTE: The expanded size of the Mountain Lion installer will NOT fit on a single-sided DVD. You MUST have a dual-sided DVD in order to burn the DVD.

UPDATE 07.26.12 – Thanks to commenter Benoit’s comments, you can now burn a single-sided/single-layer DVD. See updated instructions below.

Step One – Download the Mountain Lion installer

Head over to the Apple App Store and download the installer.


If you have already purchased Mountain Lion, check your “Purchases” section and you can download from there.


Then sit back and wait while it downloads.


Step Two – Quit the Installer Once it’s Finished Downloading & Copy

The installer will automatically launch once it is completed downloading. You need to STOP that lion in it’s tracks right there. Just select “Quit” from the “File” menu.


Then, go into your “Applications” folder and copy the Mountain Lion Installer to another location like your Desktop. (Remember to copy and not move.)


You can see that the installer is about 4.37 GB (as I mentioned before, the expanded size is LARGER than what will fit on a single-sided DVD so get a dual-sided DVD).

Step Three – Show Package Contents & Copy the Installer File

From the copy that you created of the installer (e.g., the one on your Desktop), you will need to extract the actual installer DMG from the Package Contents. To do this, right-click on the Installer file and choose “Show Package Contents”.


From within the Package Contents, navigate to: Contents > Shared Support and select the “InstallESD.dmg” file and COPY that back to your Desktop (or wherever you want). You will need this file (“InstallESD.dmg”) for the bootable DVD.


Remember the location where you put that .dmg file.

Step Four – Burn the DVD (or the USB drive)

The next step is to burn the actual DVD. As I already said a few times, you need a dual-sided DVD (see step 4a below on how to burn a single-sided DVD). I only had a single-sided DVD so I’m showing the steps here that you would use.

(Note: untested instructions for how to make a bootable USB thumb drive are below as well.)

DVD Installer

First, launch the “Disk Utility” application. Then click on the “Burn” icon.


When you click on the “Burn” icon, you will be asked which image you would like to burn. Navigate to where you saved the “InstallESD.dmg” file and select that.


Normally, your DVD would start burning at this point, however, I didn’t have a dual-layer/double-sided DVD and the expanded size of the installer just wouldn’t fit.


But if you do have a dual-layer DVD, you should then click the “Burn” button and you will shortly have a bootable Mountain Lion Installer DVD.

Step 4a – Burning a Single-Layer DVD

Thanks to comments and instructions by Benoit (in comments section below), there is now a way to burn a single-layer/single-sided DVD. I have tested this out and it seems to work. Here are the steps:

First, you need to create an empty image using Disk Utility. Click on “New Image”.


Then fill out the dialog box with:

Save As: “OSX Mountain Lion DVD”
Name: “OSX Mountain Lion DVD”
Size: Select –> “4.6 GB (DVD-R/DVD-RAM)”
Format: “Mac OS Extended (Journaled)”
Encryption: “None”
Partitions: “Single Partition – GUID Partition Map” “Single Partition – Apple Partition Map”
Image Format: “read/write disk image”

See below:

new image apple partition1 - HighTechDad™

If you new image/partition doesn’t mount, run a “Repair” on it as that will correct the issue and allow you to mount it as well as update it to make it bootable.


Next, create that image and then mount the “InstallESD.dmg” image that you had saved (to your Desktop) previously. When both are mounted, it should look something like this:


Since the mounted “InstallESD.dmg” image shows a capacity of 4.75 GB, Disk Utility can’t burn it since a single-sided DVD is less than that. So, what you need to do is actually copy the contents of the “installESD.dmg” mounted image into your newly created “OSX Mountain Lion DVD” image. At this point, you need to open your Terminal application to copy the files using the following terminal command (note: if you have spaces in the names, you need to use the “\” to denote that – slightly different than in Benoit’s comments):

cp -Rv /Volumes/Mac\ OS\ X\ Install\ ESD/* /Volumes/OSX\ Mountain\ Lion\ DVD/

(Note: Benoit did say that you can add a -p command to the command line – see the comments – I have not tested this – so it would be “cp -pvR”)

Here’s what it looks like in the Terminal:


The process of copying will take a few minutes but you will see the progress on the Terminal screen. When it it completed, and be sure you don’t have any errors, you should see something similar to this:


At this point, you can “exit” out of the Terminal app.

Now, you can BURN the single-sided DVD based on that new image that you created. Just follow the steps outlined in “Step Four – Burn the DVD” but use the newly created image instead of the “installESD.dmg” one:


And look! It’s burning on a single-layer DVD:


And it burned the single-layer DVD successfully!


I took this newly created single-layer DVD and booted my MacBook Pro off of it (holding “Option” while rebooting), so it looks like this process works. It DOES take a very long time to boot from the DVD though. Thanks again Benoit!

USB Thumb Drive Installer

If you have an 8 GB USB thumb drive, you can create an installer out of that as well. I have not tested this process but here are the steps.

  1. First you need to format the USB drive (and note that formatting will completely erase all of the contents of your USB Thumb Drive). Just go over to Disk Utility and choose the “Partition” tab.
  2. Choose “1 Partition” from the dropdown menu and choose “Mac OS Extended (Journaled)” as the format type.
  3. Click the “Options” button and select “GUID Partition Table” which will “bless” the new partition and make it bootable.
  4. Hit “Apply” which will then format (and erase) the USB Thumb Drive.
  5. Lastly, click the “Restore” tab and select the “InstallESD.dmg” file as your “source” and the USB Thumb Drive as the “destination”. Click “Apply” to put the expanded installer on the Thumb Drive.

So, in the end, you will have either a bootable DVD or USB Thumb Drive complete with that growling Mountain Lion Installer. To use either of these, insert the DVD or USB drive and restart your Mac holding down the “Option” key when you restart. You can then select your new installer from the list of options that appear on start up.

Did these steps work for you? Leave a comment! What do you think of Apple’s new Mountain Lion?

HTD says: Another Big Cat to install on your Mac! Growl!

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About HighTechDad

Michael Sheehan (“HighTechDad”) is an avid technologist, writer, journalist, content marketer, blogger, tech influencer, social media pundit, loving husband and father of 3 beautiful girls living in the San Francisco Bay Area. This site covers technology, consumer electronics, Parent Tech, SmartHomes, cloud computing, gadgets, software, hardware, parenting “hacks,” and other tips & tricks.

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