Create a Bootable OS X El Capitan Installer on a USB Flash Drive

Create a Bootable OS X El Capitan Installer on a USB Flash Drive an article by Tom Nelson

OS X El Capitan, the latest version of OS X as of the summer of 2015, is available from the Mac App Store as a free download. Like previous versions of OS X, El Capitan has the annoying habit of automatically starting the installation process once the download is complete.

This would be fine if all you wanted to do was quickly install El Capitan as an upgrade install over your existing version of OS X.

But even if this is your goal, it’s not too likely that you’re actually ready to start the install process. After all, there’s quite a bit of housekeeping to be done before you commit to installing OS X El Capitan: that includes having a recent backup of your data, and making a bootable OS X El Capitan installer on a USB flash drive.

Having a bootable installer for OS X El Capitan is a good idea, even if your plan is just to perform an upgrade install, which technically doesn’t need to be done from a separate boot device. But having your own copy of El Capitan on a separate device ensures that you’ll always be able to install or reinstall it, or perform basic Mac troubleshooting tasks, even if you have no connection to the Internet or access to the Mac App Store, should you need to re-download El Capitan.

How to Create the Bootable Installer for OS X El Capitan
There are two methods of creating the bootable installer; one involves using Disk Utility, the Finder, hidden files, and a great deal of effort and time.

If you wish to use this method, you can follow the guide How to Make a Bootable Copy USB Flash Drive of the OS X Yosemite Installer, and no, that’s not a typo. The older process outlined in the Yosemite document will work for El Capitan; you need only be aware of file name changes, such as El Capitan instead of Yosemite in the instructions.

There’s also a second method, and it’s the method I prefer, because it’s less involved, has few places where things can go wrong, and only involves using a single app: Terminal.

What You Need

First, you’ll need a copy of the OS X El Capitan installer, which is available from the Mac App Store. Until the official release of OS X El Capitan on September 30th, 2015, there will be multiple public beta versions available throughout the summer in the store. This guide will be updated as needed for each version once they become available.

Next, download the installer from the Mac App Store. Once the download is complete, the installer will start automatically. When it does, be sure to quit the installer. If you allow the installer to actually perform an installation, the installer will delete itself at the end of the process. We need the installer program to help us create a bootable installer, so don’t let the installer run.

If you have already installed OS X El Capitan, and wish to now create a bootable installer, you can force the Mac App Store to re-download the installer.

  • The El Capitan installer is downloaded to the /Applications folder, with the file name Install OS X El Capitan.
  • A 16 GB or larger USB flash drive. These instructions will also work for other suitable bootable devices. I’m going to assume that you’re using a USB flash drive, but any bootable device will work, including an external drive or internal drive.
  • A Mac that meets the OS X El Capitan Minimum Requirements.

The process of creating the bootable OS X El Capitan installer causes the USB flash drive you’re using as the destination for the installer to be erased. So, before you proceed, make sure you either have a backup of the flash drive’s contents (if any), or that you don’t care that they’ll be erased.

The Secret createinstallmedia Command

It’s not much of a secret, especially since we have used this method in the past to create bootable installers for previous versions of OS X.

But since it involves using Terminal, and entering a long command with quite a few arguments that need to be provided, it remains mostly unused, if not completely ignored, by many day-to-day Mac users. Still, it’s the easiest way to create the bootable installer, so let’s get started.

You need the OS X El Capitan installer you downloaded from the Mac App Store; make sure it’s present in the /Applications folder. If it isn’t, flip back to Page 1 of this guide for details about re-downloading the app from the store.

Create the OS X El Capitan Bootable USB Installer
  1. Connect the USB flash drive to your Mac.
  2. Give the flash drive an appropriate name. You can do this by double-clicking the device’s name on the desktop, and then typing in a new name. I suggest calling the drive elcapitaninstaller. You can use any name you wish, but it shouldn’t have any spaces or special characters. If you do select a different name, you’ll need to modify the Terminal command I outline below with the flash drive name you selected.
  3. Launch Terminal, located at /Applications/Utilities.
  4. WarningThe following command will completely erase the flash drive named elcapitaninstaller.
  5. In the Terminal window that opens, enter the following command. The command is a single line of text, though your web browser may show it displayed over several lines. If you used the drive name suggested above, you can triple-click on one of the words in the command to select the entire line of text.
    sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/elcapitaninstaller --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app –nointeraction
  6. Copy (command + C keys) the command, and then paste it (command + V keys) into Terminal. Press return or enter.
  7. You’ll be asked to provide an administrator password. Enter the password, and press return or enter.
  8. Terminal will execute the createinstallmedia command and display the status as the process unfolds. Erasing and copying the files from the OS X El Capitan installer can take a bit of time, depending on how fast the USB flash drive is. You may want to consider taking a break and stretching your legs.
  9. Once Terminal completes the command, it will display the line Done, and then show the Terminal prompt waiting for a new command to be entered.
  10. You can now quit Terminal.

The bootable OS X El Capitan installer has been created. You can use this bootable installer to perform any of the supported installation types, including an upgrade install or a clean install. You can also use it as a bootable troubleshooting tool that includes an assortment of apps, including Disk Utility and Terminal.

 

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