Locate the file named Install OS X Yosemite, and then right-click the file and select Show Package Contents. Open the Contents folder, then open the Shared Support folder. Here you will find the disk image that contains the files you need to create a bootable installer. Double-click the InstallESD.dmg file. Select the target disk and click on the install option. Type your administrator password and click OK. The installer will duplicate the needed files and then restart.

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:

* 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.

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 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.

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 that the macOS installer is in your Applications folder, then enter the appropriate path in Terminal:

Many users don’t know how to use diskmaker X. in fact, this software is very easy to use. It only takes a few steps to make Yosemite and install U disk. After downloading, double-click the DMG file to see the following interface. Diskmaker x is the same as ordinary OS X applications. We just need to drag diskmaker x to the application folder. The following editor will give you a detailed introduction to the tutorial of making Yosemite installation U disk by diskmaker X.

Step 1: Download diskmaker X. the editor provides a link to the Chinese version of diskmaker X

Create Yosemite Usb Install Disk Utility

Step 2: double click to start diskmaker X. in the first interface, the software will ask which system installation U disk needs to be made. Currently, it supports 10.8, 10.9 and 10.10. Select Yosemite (10.10).

Step 3: diskmaker x will automatically detect Yosemite installation files. If it has been downloaded through the MAC app store, diskmaker x will be found in the application folder. If you download from the Internet disk, you can use use another copy to locate the Yosemite installation file manually.

Step 4: then, we need to choose to install U disk. Diskmaker x supports U disk and other external storage. A U disk with a capacity of 8GB is enough.

Step 5: then diskmaker x will list all the drives connected to the Mac, and select the U disk you insert. Be careful not to choose the wrong one. Diskmaker x will format the U disk.

Os X Yosemite Install Hdd

Step 6: after the selection, confirm the U disk to be formatted again. Then select erase then create the disk to format and create the installation U disk.

Step 7: diskmaker x will prompt for administrator permission, and then just enter the password.

Step 8: the rest is a long time. Diskmaker x will automatically start the creation process of Yosemite installation U disk. The creation time is related to the speed of copying files to USB flash disk. As long as you wait patiently, you can see that a window will appear behind diskmaker X and the files will be copied automatically.

After that, diskmaker x will pop up a prompt. At this time, we can restart the Mac, press and hold the option button, and select the Yosemite installation U disk that has just been made.