As with last year, there are two ways to get it done. There's the super easy way with the graphical user interface and the only slightly less easy way that requires some light Terminal use. Here's what you need to get started.
- A Mac that you have administrator access to, duh. We've created El Capitan USB stick from both Yosemite and El Capitan, but your experience with other versions may vary.
- An 8GB or larger USB flash drive or an 8GB or larger partition on some other kind of external drive. For newer Macs, use a USB 3.0 drive—it makes things significantly faster.
- The OS X 10.11 El Capitan installer from the Mac App Store in your Applications folder. The installer will delete itself when you install the operating system, but it can be re-downloaded if necessary.
- If you want a GUI, you need the latest version of Diskmaker X app. Version 5 is the one with official El Capitan support...
Once you've obtained all of the necessary materials, connect the USB drive to your Mac and run the Diskmaker X app. The app will offer to make installers for OS X 10.9, 10.10, and 10.11, and it should run on OS X versions all the way back to 10.7—support for 10.6 was dropped in the most recent release.
Diskmaker X has actually been around since the days of OS X 10.7 (it was previously known as Lion Diskmaker), and it's still the easiest GUI-based way to go without intimidating newbies. If you're comfortable with the command line, it's still possible to create a disk manually using a Terminal command, which we'll cover momentarily.
Select OS X 10.11 in Diskmaker X, and the app should automatically find the copy you've downloaded to your Applications folder. It will then ask you where you want to copy the files—click "An 8GB USB thumb drive" if you have a single drive to use or "Another kind of disk" to use a partition on a larger drive or some other kind of external drive. Choose your disk (or partition) from the list that appears, verify that you'd like to have the disk (or partition) erased, and then wait for the files to copy over. The process is outlined in screenshots above.
The only slightly less-easy way
If you don't want to use Diskmaker X, Apple has actually included a terminal command that can create an install disk for you. Assuming that you have the OS X El Capitan installer in your Applications folder and you have a Mac OS X Extended (Journaled)-formatted USB drive named "Untitled" mounted on the system, you can create an El Capitan install drive by typing the following command into the Terminal.
sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app --nointeraction
The command will erase the disk and copy the install files over. Give it some time, and your volume will soon be loaded up with not just the OS X installer but also an external recovery partition that may come in handy if your hard drive dies and you're away from an Internet connection.
Whichever method you use, you should be able to boot from your new USB drive either by changing the default Startup Disk in System Preferences or by holding down the Option key at boot and selecting the drive. Once booted, you'll be able to install or upgrade El Capitan as you normally would.