Creating a bootable USB drive Mac OS X installer can save you time and bandwidth when you have a few Macs you want to update or you want a backup copy of your operating system installer. Fortunately, it’s pretty straight forward to create a USB installer for the latest OS X El Capitan, currently in beta, and the process is the same as OS X 10.10 Yosemite. You will have to apply and be accepted into the OS X Beta program to get access to the early preview of the operating system but this same process applies to the final versions of OS X.
You will need at least an 8GB USB flash drive as the El Capitan beta is a 6GB download. You will need to download the OS X 10.11 install through the Mac App Store by redeeming your code from the beta program. Once the download completes, do not continue with the install. Instead, follow these steps to create your USB bootable drive.
Insert your USB drive to the Mac. Select the drive and format your USB drive as Mac OS X extended (journaled) using Disk Utility.
With an administrator account that has a password set, open up terminal and run this command:
If you’re using the Beta installer:
sudo "/Applications/Install OS X El Capitan Public Beta.app/Contents/Resources/createinstallmedia" --volume /Volumes/Untitled --applicationpath "/Applications/Install OS X El Capitan Public Beta.app" --nointeraction
If you’re using the OS X Yosemite Final release:
sudo "/Applications/Install OS X El Capitan.app/Contents/Resources/createinstallmedia" --volume /Volumes/Untitled --applicationpath "/Applications/Install OS X El Capitan.app" --nointeraction
Give it about 20 minutes to complete and your drive will be completed afterwards.
Your USB drive should now be ready to go.
Insert your USB drive into a compatible Mac and hold down the option key while the Mac is booting up.
Select the “Install OS X El Capitan” drive and the boot will continue until it loads the OS X Utilities.
Select Install OS X and continue through the OS X 10.11 install wizard.