Most USB flash drives are formatted for use with Windows. Before you can install OS X on a USB flash drive, you will need to change the drive’s formatting to the standard used by OS X (Mac OS X Extended Journaled).
Format Your USB Flash Drive
- Insert the USB drive and select the “Finder” menu.
- Select “Applications” from the right side of the menu. This will show the contents of the Applications folder. Select the “Utilities” folder, which is nested in the Applications folder, to show the folder’s contents. Double-click “Disk Utility.”
- Select the drive that you wish to manage in “Disk Utility.” The available drives will be listed in the left column. Click on the drive labeled “USB Flash.”
- Click on the “Erase” tab at the top of the utility to show the formatting and naming options for your drive. Give your USB drive a name by typing it into the field provided. Select “Mac X Extended (Journaled)” or “MS-DOS (FAT)” as the volume format. MS-DOS (FAT) is a format that can be read on both Macs and PCs. Mac X Extended (Journaled) was created to increase transfer rates.
- Click the “Erase” button on the lower-right side of the screen to begin the formatting process.
Enable Ownership of Your USB Flash Drive
In order for a drive to be bootable it must support ownership, which is the ability of files and folders to have specific ownership and permissions.
- Locate the USB flash drive on your Mac desktop, right-click its icon, and select ‘Get Info’ from the pop-up menu.
- In the Info window that opens, expand the ‘Sharing & Permissions’ section, if it’s not already expanded.
- Click the lock icon in the bottom right corner.
- Enter your administrator password when asked.
- Remove the check mark from ‘Ignore ownership on this volume.’
- Close the Info panel.
If you want to format USB flash drive on Windows, try Partition Manager.