Create El Capitan Installer

A bootable installer is one of the fastest ways to install El Capitan. Rather than copy the installer to a local drive you can run it right off a USB disk (or Thunderbolt if you dare). Such a little USB drive would be similar to the sticks that came with the older MacBook Air, when we were all still sitting around wondering how you would ever install the OS on a computer with no optical media or Ethernet otherwise. Luckily, Apple loves us. To make a bootable USB/flash drive of El Capitan like the one that used to come with the MacBook Air, first name the USB drive. I’ll use mavinstall for the purposes of this article. The format should be Mac OS Extended Journaled. The installer is called Install OS X El Capitan and is by default located in the /Applications directory. Inside the app bundle, there’s a new binary called createinstallmedia (nested in Contents/Resources). Using this binary you can create an installation drive (similar to what we used to do with InstallESD). To do so, specify the –volume to create the drive on (note that the target volume will be erased), the path of the Install OS X El Capitan app bundle and then we’re going to select –nointeraction so it just runs through the whole thing

I have downloaded the El Capitan dmg file (InstallMacOSX.dmg) provided by Apple.The expanded dmg image contains the package 'InstallMacOSX.pkg' which should be run to create the El Capitan installer but fails with the following message: This version of OS X 10.11 cannot be installed on this computer. The installer you create can be used to install OS X El Capitan 10.11 on any eligible Mac computer. This is a more convent and less time consuming way to install OS X El Capitan on multiple machines, gives you a handy emergency disk, and enables a fresh OS X install.

/Applications/Install OS X El Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/mavinstall --applicationpath /Applications/Install OS X El Capitan.app --nointeractionNote: You’ll need to elevate your privileges for this to run. Once run you’ll see that it erases the disk, copies the Installation materials (InstallESX, etc) and then makes the drive bootable, as follows: Erasing Disk: 0%... 10%... 20%... 100%... Copying installer files to disk... Copy complete. Making disk bootable... Copying boot files... Copy complete. Then you can either select the new volume in the Startup Disk System Preference pane or boot the computer holding down the option key to select the new volume. Note: If you can do this on a system with a solid state drive it will be faster. Although this took 17 minutes last I ran it even then so be patient for the files to copy.

These advanced steps are primarily for system administrators and others who are familiar with the command line. You don't need a bootable installer to upgrade macOS or reinstall macOS, but it can be useful when you want to install on multiple computers without downloading the installer each time.

What you need to create a bootable installer

  • A USB flash drive or other secondary volume formatted as Mac OS Extended, with at least 14GB of available storage
  • A downloaded installer for macOS Big Sur, Catalina, Mojave, High Sierra, or El Capitan

Download macOS

  • Download: macOS Big Sur, macOS Catalina, macOS Mojave, or macOS High Sierra
    These download to your Applications folder as an app named Install macOS [version name]. If the installer opens after downloading, quit it without continuing installation. To get the correct installer, download from a Mac that is using macOS Sierra 10.12.5 or later, or El Capitan 10.11.6. Enterprise administrators, please download from Apple, not a locally hosted software-update server.
  • Download: OS X El Capitan
    This downloads as a disk image named InstallMacOSX.dmg. On a Mac that is compatible with El Capitan, open the disk image and run the installer within, named InstallMacOSX.pkg. It installs an app named Install OS X El Capitan into your Applications folder. You will create the bootable installer from this app, not from the disk image or .pkg installer.

Use the 'createinstallmedia' command in Terminal

  1. Connect the USB flash drive or other volume that you're using for the bootable installer.
  2. Open Terminal, which is in the Utilities folder of your Applications folder.
  3. Type or paste one of the following commands in Terminal. These assume that the installer is in your Applications folder, and MyVolume is the name of the USB flash drive or other volume you're using. If it has a different name, replace MyVolume in these commands with the name of your volume.

Big Sur:*

Catalina:*

Mojave:*

High Sierra:*

El Capitan:

Capitan

* If your Mac is using macOS Sierra or earlier, include the --applicationpath argument and installer path, similar to the way this is done in the command for El Capitan.


After typing the command:

  1. Press Return to enter the command.
  2. When prompted, type your administrator password and press Return again. Terminal doesn't show any characters as you type your password.
  3. When prompted, type Y to confirm that you want to erase the volume, then press Return. Terminal shows the progress as the volume is erased.
  4. After the volume is erased, you may see an alert that Terminal would like to access files on a removable volume. Click OK to allow the copy to proceed.
  5. When Terminal says that it's done, the volume will have the same name as the installer you downloaded, such as Install macOS Big Sur. You can now quit Terminal and eject the volume.

Use the bootable installer

Determine whether you're using a Mac with Apple silicon, then follow the appropriate steps:

Apple silicon

  1. Plug the bootable installer into a Mac that is connected to the internet and compatible with the version of macOS you're installing.
  2. Turn on your Mac and continue to hold the power button until you see the startup options window, which shows your bootable volumes.
  3. Select the volume containing the bootable installer, then click Continue.
  4. When the macOS installer opens, follow the onscreen instructions.
Capitan

Intel processor

Create El Capitan Installer From Catalina

  1. Plug the bootable installer into a Mac that is connected to the internet and compatible with the version of macOS you're installing.
  2. Press and hold the Option (Alt) ⌥ key immediately after turning on or restarting your Mac.
  3. Release the Option key when you see a dark screen showing your bootable volumes.
  4. Select the volume containing the bootable installer. Then click the up arrow or press Return.
    If you can't start up from the bootable installer, make sure that the External Boot setting in Startup Security Utility is set to allow booting from external media.
  5. Choose your language, if prompted.
  6. Select Install macOS (or Install OS X) from the Utilities window, then click Continue and follow the onscreen instructions.

Create Bootable El Capitan Installer

Learn more

A bootable installer doesn't download macOS from the internet, but it does require an internet connection to get firmware and other information specific to the Mac model.

Create El Capitan Installer Terminal

For information about the createinstallmedia command and the arguments you can use with it, make sure that the macOS installer is in your Applications folder, then enter the appropriate path in Terminal: