• Use Snow Leopard to create the Install OS X El Capitan application. Use Snow Leopard to create the El Capitan USB installer (El Capitan rescue USB). Note: In your case, you probably could avoid creating the El Capitan USB installer the and just run the Install OS X El Capitan application on the 2008 iMac.
• Create Bootable Usb El Capitan Without Terminal Plug the bootable installer into a Mac that is connected to the internet and compatible with the version of macOS you're installing. Press and hold the Option (Alt) ⌥ key immediately after turning on or restarting your Mac.

These advanced steps are primarily for system administrators and people 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 it on multiple computers without having to download the installer each time.

What you need to create a bootable installer

Now Create bootable USB for Mac OS El Capitan on Windows. Now it is the time to create a bootable USB installer using TransMac, To install Mac OS El Capitan on VirtualBox on Windows 10 you need a Bootable USB here you will learn the steps of creating a bootable USB installer for Mac OS El Capitan on Windows.

• A USB flash drive or other secondary volume formatted as Mac OS Extended, with at least 14 GB 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 will be downloaded to your Applications folder as an app called Install macOS [version name]. If the installer opens after download, quit it without continuing the 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. For enterprise administrators, please download from Apple, not a locally hosted software update server.
• Download: OS X El Capitan
  This will be downloaded as a disk image called InstallMacOSX.dmg. On a Mac that is compatible with El Capitan, open the disk image and run the installer within, which has the name 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

El Capitan Usb Creator Tool

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:

* If your Mac is using macOS Sierra or earlier, include the --applicationpath argument and installer path, similar to the way this was 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 displays the progress as the volume is being erased.
4. After the volume has been erased, you may see an alert stating that Terminal would like to access files on a removable volume. Click OK to allow the copy to proceed.
5. When Terminal says it's finished, 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

Usb El Capitan Dmg File

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.

Intel processor

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 displaying 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 the External Boot setting in Startup Security Utility has been 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.

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.

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

DiskMaker X (formerly Lion DiskMaker) is an application built with AppleScript that you can use with many versions of OS X to build a bootable drive from OS X installer program (the one you download from the App Store). As soon as you launch the application, it tries to find the OS X Install program with Spotlight. Then, it proposes to build a bootable install disk and make it look as nice as possible. It’s the easiest way to build an OS X Installer in a few clicks ! Then you can use the Install drive to fully re-install the OS on a freshly formated drive, or install it on your many Macs without re-downloading the full installer.

Jump over the break to learn how to use DiskMaker X…

1. Get an an empty flash drive with at least 8GB of storage

2. Download OS X El Capitan

3. Download DiskMaker X

4. Double-click on the .dmg file to open it and drag-and-drop the DiskMaker X app into the Applications folder

5. Now load DIskMaker X. When you load the app, it will ask you which version of OS X do you want to make a boot disk of. You can choose Mavericks, Yosemite and of course, El Capitan. We’ll choose El Capitan

6. Now, the app will search for a copy of OS X El Capitan. Once it found your El Capitan copy, it will ask you if you want to use the copy that it found or you want to use another copy. If you downloaded it from the app store ( step 2 ), choose ‘Use this copy’

7. Now the app will ask you about your thumb drive, and it will tell you that will be completely erased before copying OS X El Capitan onto it…

8. Now the app will format your flash drive and ask you for your admin password. Once you enter your admin password, DiskMaker X will start copying the necessary El Capitan files onto your flash drive.

El Capitan Usb Creator Code

NOTE: this process will take a while. Be patient….

El Capitan Usb Creator

9. When you’re done, the app will tell you that the boot disk is ready, you’ll see that your flash drive has been renamed as OS X 10.11 Install Disk and it will be opened. Now all you have to do is restart your Mac and and after you here the chime sound, press the Option ( Alt ) key until you see the option to choose the flash drive to boot from.