Bootable Usb For Mac Os X Mountain Lion


On every OS X 10.8 Mountain Lion there is a hidden partition to enable a method for Mountain Lion OS to be reinstalled on the machine, it is known as the Recovery Partition or drive and is 650mb in size.

How to make a Mac OS X Lion bootable Thumb/Flash/USB Drive for free. All you need is a 4GB Flash Drive and the OS X Install package Any questions post below. When done, your USB is ready with the installer. We will now run through installation. Installing Mountain Lion on PC. Prepare BIOS: Now take this Bootable USB and plug to the PC where you wish to install it.Power ON system and hit F12 (or whatever shortcut you’ve for your PC to boot into BIOS) and then Enable boot from USB, and raise its priority to the highest. As you want to create a LiveUSB you need a.iso image to make it. The Mac image is a.dmg file, so you must to convert this file into.iso, and then install it. Install DMG2IMG. DMG2IMG (1, 2) will convert the.dmg image into a.iso image. To install open a terminal and enter this command: sudo apt-get install dmg2img Convert the Image.

If you bought a new machine from Apple you have OS X 10.8 already installed – but no back up disk! and since you haven’t bought the OSX Lion 10.8 App from the App store you can’t re-download it – so thats why you have the recovery drive as a partition in your main hard drive, to boot from it you need to restart the machine and when it starts to boot hold down “command” + “r” keys.

From the Recovery Partition Hard Drivr you can run Disk Utility, access the command line, get online help and do a restore from a Time Machine backup and re-install Mountain Lion leaving all your other files intact – it just replaces the core operating system.

You can make a bootable USB drive or disk from the Recovery Partition 2 ways – the easy way and on the Terminal

The Easy Way

1) Download OSX Recovery Disk Assistant and uncompress and launch it

2) Attach the USB drive that you want to copy the Recovery Partition to.

3) Select the drive and continue (All contents on it will be erased)

That’s it one external bootable Recovery Drive – this works on both OSX 10.7 and 10.8

The Terminal Way

1) Launch Terminal from /Applications/Utilities and run:

The main drive in this list is No.2 with the “Identifier” of disk0s2, the boot Recovery HD drive is disk0s3

We can also identify the Recovery drive by the name and the size – set at 650mb

2) Mount the drive by its Identifier:

Output should be:

Now the Recovery HD is mounted in the Finder and you can see it in the sidebar under Devices
Navigate to it from the sidebar – Recovery HD/


3) Doubleclick BaseSystem.dmg to mount it also in the sidebar. This will mount the volume ” Mac OSX Base System”


4) Open Disk Utility in /Applications/Utilities

5) Put in a 2GB+ USB drive, let Disk Utility load it. The USB drive needs to be formatted as Mac OS Extended Journaled, if its not, its time to format it in Disk Utility…

6) Finally in still in Disk Utility, select the “Restore” tab – drag the mounted volume “Mac OSX Base System” into the Source field and drag the USB drive “Volume” (mine is called SuperBootUSBDrive) to the Destination.


7) Click Restore – 10 minutes later – One bootable USB drive

Your bootable USB drive will be called “Mac OS X Base System” after the restore is complete. Now to boot from it just select it as the Start Up disk in System Preferences or hold down option key on boot and select it from the choice of bootable devices.

If you have downloaded the OSX 10.8 Mountain Lion App from the App Store then you can also make a full bootable image of OSX 10.8 to a disk/drive, you need to make the boot drive/disk before you install the Mountain Lion App, as the installer is deleted after running it. That’s why the guide here can get you out of trouble.

Update For Newer Models – hidden BaseSystem.dmg – BaseSystem.chunklist

If you have the latest models from Apple that came already shipped with OSX 10.7, then you may not have the “BaseSystem.dmg” but instead see a “BaseSystem.chunklist” , the “BaseSystem.dmg” is there it’s just hidden.


To show it so you can see it in the finder – go to Terminal – and after you have mounted the Recovery Drive:

Now it will be visible in the Finder.

This is the process I used to make a bootable USB drive of the Mountain Lion Operating System on my Macbook Pro. My Macbook was the Macbook Pro 13″ inch 2012 model. This process for making a boot drive can work for other Macbook types too. Difficulty rating 2/10, maybe even 1/10, super easy!

This is the process I used to create a bootable USB drive of Mountain Lion OS X for my Macbook pro.

Why Make A Bootable USB Install Drive for Mac Mountain Lion OS?

The main reason to make the bootable USB drive is to not have to download the 4GB file every time you want to do a reinstall of the Mountain Lion operating system.

The second reason to make a bootable USB OS drive is it makes reinstalling the operating system faster. Using a USB drive method without the downloading makes a full reset take 30 minutes. Without the USB drive it will take hours.

Tools you will need:

  • Macbook Pro. I have not tested this with other Macs, it should work 9/10.
  • Internet Connection to download the 4GB Mountain Lion install file from Apple.
  • OS DOWNLOAD USB DRIVE. 12GB or more USB Flash Drive. I used a 32GB USB drive, 12GB is the minimum amount of Geebees you need. More is okay, like 32GB is fine.
  • OS BOOT USB DRIVE. Optional 8GB or more Flash drive for a permanent USB drive, or you can reuse the OS DOWNLOAD DRIVE. This is optional because you can copy the files onto your hard drive and then on to the OS DOWNLOAD USB flash drive again whenever you need it. I used a separate 8GB USB Flash drive for my OS BOOT DRIVE to keep a permanent solution. I got my 8GB USB drive from Ebay for $6.

No extra Mac software is required to make or use the USB boot drive method.

Preparing the USB drive

Turn the Macbook pro ON. Insert the OS DOWNLOAD USB Flash Drive into the Macbook Pro.

Open the Disk Utility Program. (Hold the CMD key and press space bar -> Type “disk utility” without the quotes -> select disk utility from the list that is shown).

Now we will partition the OS DOWNLOAD USB drive and make it bootable. In disk utility, select your OS DOWNLOAD drive on the left panel by clicking on it. Make sure you click on the part of it that is most to the left on the left panel. Not the sub heading of it, the main heading. The main part that might say something like “28.36 GB NAMEOFCOMPANY”.

Now in the big panel on the right choose partition at the top, it should be the middle tab, between Erase and RAID. If you do not see the option to partition you did not click the correct drive on the left or clicked the sub heading. Make sure you clicked the main entry for the Flash drive.

In the partition area first click on the “choose” above the big box (in the “volume scheme” area) and change it to “1 partition”. Then click options just below this box and select the GUID partition table option, then click OK.

Now on the right of this area enter a name for your drive, like “OS X Installer” and change the format to “Mac OS Extended (Journaled). When you’re happy choose Apply and agree to the question that asks if you are happy to erase the Flash drive. Check to make sure it is the correct drive before agreeing! I am not responsible for your mistakes here!

Once it is complete you will have a clean USB drive ready for the Lion Operating system download.

End of formatting and partitioning the OS DOWNLOAD USB drive procedure.

Downloading the OS Install Files From Apple

Now with the formatted and partitioned OS DOWNLOAD USB DRIVE inserted shut down the macbook pro. Once the Macbook pro is off hold the CMD and r keys. Now turn on the Macbook pro while keeping hold of the CMD and r key. This will activate the Macbook Pro restore feature. Every Macbook Pro has this feature to reinstall the operating system at anytime.

Once it has loaded, release the CMD+r keys and choose the second option – “Reinstall Mac OS X”, and hit continue. Now it will ask for verification through your internet connection. Agree to this and select YOUR USB FLASH DRIVE AS THE LOCATION to install. This is important because we want to download the files from Apple onto our USB drive. Once you agree, it will start the download.

Make Bootable Mountain Lion Usb


Once the download is complete you must pull out the USB Flash drive as soon as the black screen shows. If the screen is black, pull out the flash drive! Don’t wait, just pull it out. If you wait it will start the installation and delete the files from the USB and you’ll have to do it all again. You need these installation files to create a bootable USB Lion drive. So, once the timer is close to 0 BE READY. A few seconds after the timer goes to zero seconds remaining the the screen will turn black. Remove the USB at the black screen! Not before, and not after.



Create bootable usb for mac os x mountain lion

You pulled out? great. Now you have a USB Flash drive with OS Mountain Lion! That was the hard part completed, now the easy stuff.

Keeping the OS DOWNLOAD USB drive OUT of the Macbook pro and start the Macbook. It will load as normal. Press CMD+SPACEBAR and type “disk utility”, then select disk utility from the list. Now insert your USB drive with the operating system on it. Copy all the files from it to any location on your hard drive. I copied them into the Download folder, but you can put them anywhere you like.

Os x lion usb

Now open the folder you copied onto your hard drive. Look inside and you will find a big 4GB file ending in .dmg. This is the main file you need.

Insert your OS BOOT USB DRIVE. You should have already partitioned this drive, with a GUID and with “Mac OS Extended (Journaled)”. Use the usb guide above to do this. If you are reusing your OS DOWNLOAD DRIVE partition and format it again using the above procedure once you have copied the operating system folder to your hard drive (we just did this in the last paragraph!).

Click on this big .dmg file to open and it will mount the .dmg file. Now go back to disk utility. You should have your OS BOOT USB DRIVE attached to your Macbook Pro and you will see the “InstallESD.dmg” file shows as mounted at the bottom of the left panel of disk utility.

Bootable Usb For Mac Os X Mountain Lion 10.7

Click on the InstallESD.dmg file on the left. At the top of the right pane choose “restore”. It shows two area you need to enter. Source and Destination. Source should already be filled with InstallESD.dmg. If it is not, then enter that now by browsing to the big file and inserting it into the Source box.

For the destination we want our BOOT USB DRIVE. So drag and drop that from the left panel to the Destination part.

When you are happy click the restore button to start the restore process. This takes around 30 minutes. Once complete you have your complete USB BOOT DRIVE!


To use the USB boot drive on your Macbook Pro, first insert the drive into the Macbook. Then shut down, or restart the computer. As it is turning on hold down the ALT key. This will show a special screen allowing you to select a startup disk drive. Select the USB drive (it is usually orange). The Macbook will shut down and restart using the USB drive as the Boss.

Create Bootable Usb Stick Mac Os X Mountain Lion

There was a problem installing Mac OS X, try reinstalling. If you get this error you will need to zap PRAM. This sounds bad, but it’s nothing really. Simple instructions for zapping P RAM below.

To zap PRAM shut down the Macbook Pro. Now hold down CMD+OPTION+p+r and turn on the Macbook Pro. OPTION is the “Left ALT” key and has a small bird symbol. It is near the CMD key on the left of a Macbook Pro keyboard.

When you turn on the Macbook Pro with the above keys held it will quickly reset and the screen will go to full brightness. This is the indicator that the PRAM has been cleaned. The PRAM holds simple hardware variables, like brightness level and it’s a safe procedure recommended on the Apple website. I take no responsibility if any of the advice here or on this website damages anything! I have completed every step here myself and have no fear doing it again, it is safe as far as I am concerned.

After zapping the PRAM insert the Installer USB Flash Drive into the Macbook Pro and turn off. Then turn on again while holding the ALT key on the left of the keyboard. Yes, just the ALT key and nothing else. The ALT key is near the Cmd key which is on the left of the space bar. Just hold this ALT key and start the Macbook Pro.

Bootable Os X Lion Download

When it starts it will show you some hard drive options. Choose the orange Hard drive that represents your USB drive. Click it and it will take you to the install Lion screen. Now just follow the simple instructions to complete the installation of Lion! It takes about 8 minutes to prepare installation and 35 minutes to complete the installation process itself. You Macbook Pro will restart when the process is complete.

Congratulations! You have used a Bootable USB Flash Drive to Install Mountain Lion OS X. You can now repeat this process at any time to reinstall OS X on your Macbook Pro without needing an internet connection. This process can work for other Macbook Pro versions too.

Leave a comment below if you found this guide useful or want to clear anything I missed, thanks

Mountain Lion Bootable Usb

This is the end of the guide on how to make a bootable Mountain Lion USB Install Drive.

How To Make Bootable Mac Os Usb