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.

Jul 25, 2012 Make a Bootable USB Drive of OS X 10.8 Mountain Lion from the Recovery Hard Drive July 25, 2012 20 Comments 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. Bootable Lion Usb From Dmg File A DMG disk image file is Apple's container format for capturing entire drives or disks, similar to ISO for other platforms like Windows. It consists of data blocks that represent a physical disc. If you're on a Windows machine, you're limited in what you can do with DMG files. For Windows or Linux, you will need to use different methods. For example, if you want to burn a DMG file to USB on a Mac, it’s as easy as using the built-in Disk Utility tool. On Linux and Windows, you obviously have to use other ways. Step 3 Create Bootable USB from macOS Install Image Click “Load DMG” to import your DMG file into the. Convert DMG to ISO and Make Bootable USB from ISO. Since Windows doesn't offer native.

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.

IMPORTANT PART!

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.

Survival guide how to. END OF IMPORTANT PART!

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.

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.

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.

Bootable Lion Usb From Dmg Software

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!

How To Use Your OS X 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 d