Download Article
Easy-to-follow steps for booting a Mac from a USB drive
Download Article
CD/DVD drives are disappearing from computers, leaving USB storage as the only option when re-installing an operating system. The process is fairly painless and, if you have a bit of time and patience you can complete the task on a Mac.
Things You Should Know
- Get your version of macOS from the App Store and create a backup of it on your desktop.
- Right-click the file on your desktop and make a bootable USB drive.
- Go to Package Contents in that file and go to "Disk Utility", then drag the "InstallESD.dmg" file in that package to Disk Utility.
Steps
Download Article
-
Download the Mac OS X Lion Installer from the App Store. The latest versions of the Mac operating system are only available through the App Store. -
The download can take some time depending on your internet connection. Don't worry if you lose connection halfway through download, it will resume as soon as you are re-connected to the App Store.Advertisement -
Make a backup of the installer you downloaded from App Store and save it on your desktop. Under no condition should you work on the original installer file. -
Use the backup file to make a bootable USB drive. -
Right-click on the installer file and click on "Show Package Contents". -
This will open a new window with the contents of the installer file. -
Navigate to Contents » SharedSupport. -
You’ll see a disk image called “InstallESD.dmg.” This is your ticket to creating a bootable copy of OSX Mountain Lion. -
Click on the magnifying glass icon in the menu bar and type "Disk Utility". -
Click on "Disk Utility" Application and wait for it to open. -
Drag the “InstallESD.dmg” file from installer folder into the white box on the left side of Disk Utility, and the disk image will be added. -
Connect your USB drive to the Mac using the provided USB slots. -
Wait for it to be recognized and displayed on the desktop. -
Select the USB drive from the list in Disk Utility. -
Click on Erase . -
Ensure it’s partitioned as “Mac OS Extended (Journaled)” under the “Partition” section in Disk Utility. -
The name will be "Untitled" by default, you are free to change it as per your liking. -
Click on Erase in the bottom right corner. -
Wait for USB disk to be erased and restored to single clean and usable partition. -
Click on the InstallESD.dmg icon on the left side of Disk Utility app. -
Click on the Restore tab in the center-top part of Disk Utility App. “InstallESD.dmg” should already be present in the source tab. -
Drag the drive you just added to Disk Utility from the source list in the top left of the app white space to the “Destination” path. -
Hit Restore and let Disk Utility work its magic. This can take some time so please be patient. -
Close Disk Utility. You now have a bootable USB disk drive with Mac OS X Mountain Lion installed and good to go! -
Restart the computer you wish to boot from this disk. -
While restarting, hold down the ⌥ Option key. -
Select the Installer app from the menu and you will be able to boot from it. -
Congratulations! You can now use this disk to verify/repair disk partitions, repair current installed OSX, upgrade to new OSX, or perform a clean install of existing or better OSX.
Advertisement
Community Q&A
Search
-
QuestionWhat button combination do I use to get the boot menu on a Mac G4?OPJustinCommunity AnswerHolding the "alt" (option) key should open Apple's native boot menu. That should list available drives to boot from.
-
QuestionOnce I get to Step 28 - then what? That's what I'm trying to figure out, and all the how-tos take you to that step and then end. What do I do?Community AnswerThat's just the OS utilities menu. If you restart, it should boot into the normal OS.
Ask a Question
200 characters left
Include your email address to get a message when this question is answered.
Submit
Advertisement
Video
Tips
- There are some third party apps like "Lion Disk Maker" which specialize in creating bootable disk for Mac.Thanks
- Always insist on original software as supplied by Apple Inc. and downloaded from Mac App Store.Thanks
Submit a Tip
All tip submissions are carefully reviewed before being published
Name
Please provide your name and last initial
Thanks for submitting a tip for review!
Advertisement
Warnings
- Always keep a backup of your installer file before copying to USB/external drive.Thanks
- A bootable Mac disk will work on Mac Computers ONLY.Thanks
- Always backup your system using Time Machine before installing any new OSX.Thanks
- Do not disconnect the USB drive in the middle of the entire process.Thanks
Advertisement
Things You'll Need
- 8GB+ USB external drive
- Mac OSX Installer from App Store
About This Article
Thanks to all authors for creating a page that has been read 483,383 times.
Advertisement
