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.

Mar 12, 2020 Connect the USB flash drive or other volume that you're using for the bootable installer. Make sure that it has at least 12GB of available storage and is formatted as Mac OS Extended. Open Terminal, which is in the Utilities folder of your Applications folder. Type or paste one of the following commands in Terminal.
Mar 27, 2020 This article will help you make the bootable USB pen drive unbootable in Windows or Mac that too with as many methods we know exist. You can choose the easiest one from any of the methods mentioned below and format bootable USB pen drive using cmd. Here’s how you can convert a bootable pen drive back into a normal one.

Download macOS

Find the appropriate download link in the upgrade instructions for each macOS version:

Jul 07, 2020 A trial copy of the TransMac software. One high quality USB flash drive with 16GB of storage. A copy of Apple’s macOS (DMG file). Create macOS bootable USB installation media. To create a bootable USB drive with macOS, use these steps: Download and install TransMac on your Windows PC. Jan 09, 2018 Method #1: Create Windows 10 Bootable USB/DVD on Mac Using Disk Utility. Instead of trying out with an external agent, it would be better to make use of the in-built application of Mac, called Disk Utility to burn the ISO image files on disk to make them bootable. It'll make your Mac boot from USB in just a few clicks. Starting with Disk Drill 3, anyone can create a bootable Mac OS X drive in a matter of minutes. Make sure you have an extra storage device, which is at least 2GB in size. Connect it to any Mac, run Disk Drill and use.

macOS Catalina, macOS Mojave, ormacOS High Sierra
Installers for each of these macOS versions download directly to your Applications folder as an app named Install macOS Catalina, Install macOS Mojave, or Install macOS High Sierra. If the installer opens after downloading, quit it without continuing installation. Important: 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.

OS X El Capitan
El Capitan downloads as a disk image. 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

Connect the USB flash drive or other volume that you're using for the bootable installer. Make sure that it has at least 12GB of available storage and is formatted as Mac OS Extended.
Open Terminal, which is in the Utilities folder of your Applications folder.
Type or paste one of the following commands in Terminal. These assume that the installer is still 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.
Catalina:*
Mojave:*

High Sierra:*
El Capitan:
Press Return after typing the command.
When prompted, type your administrator password and press Return again. Terminal doesn't show any characters as you type your password.
When prompted, type Y to confirm that you want to erase the volume, then press Return. Terminal shows the progress as the bootable installer is created.
When Terminal says that it's done, the volume will have the same name as the installer you downloaded, such as Install macOS Catalina. You can now quit Terminal and eject the volume.

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

Use the bootable installer

After creating the bootable installer, follow these steps to use it:

Plug the bootable installer into a compatible Mac.
Use Startup Manager or Startup Disk preferences to select the bootable installer as the startup disk, then start up from it. Your Mac will start up to macOS Recovery.
Learn about selecting a startup disk, including what to do if your Mac doesn't start up from it.
Choose your language, if prompted.
A bootable installer doesn't download macOS from the Internet, but it does require the Internet to get information specific to your Mac model, such as firmware updates. If you need to connect to a Wi-Fi network, use the Wi-Fi menu in the menu bar.
Select Install macOS (or Install OS X) from the Utilities window, then click Continue and follow the onscreen instructions.

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Learn more

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

Catalina:

Mojave:

High Sierra:

El Capitan:

Learning how to create a bootable macOS installation disk can be helpful in a variety of situations. Rather than download and install a new OS from Apple's servers each time, it can be used for multiple installations on different machines. It can also help in situations where the operating system is corrupted or installation from app store shows errors.

To create a bootable macOS installation disk, you have to burn the DMG file to a USB drive as CD/DVD is not available for Mac computers. Here's how to do it from text commands and using a purpose-built software called WizDMG. You will first need to download the DMG file for the macOS version you wish to install. For example, if you want to create a bootable macOS Mojave installer, you will need the DMG file for macOS Mojave. Once the file has been downloaded to your PC, you can proceed with one of the bootable disk creation methods shown below.

Method 1: How to Create Bootable USB Installer for Mac via Commands

macOS (formly named Mac OS X) is just a variant of popular Unix based operating system. This means a lot of daily and advanced tasks on Mac can be done via text commands such as creating bootable USB installer for Mac. However, this could be a lot of challenges if you had no clue about commands and I suggest taking a look at the other solutions in this post to avoid messing up the computer with the wrong commands.

Step 1. Search macOS name in app store (Mojave, High Serria, EI Capitai). Click 'Get' button to download the installer image on your Mac. The downloaded file will be located in Application folder.

Step 2. When the download is completed, the installation windows opens automatically, just close the window and go to Application folder. You will find a file started Install, such as Install macOS Majave.

Step 3. Now connect an external flash drive with more than 16G free space. And backup the data in that USB drive as the installer erase all content from it. Open Disk Utility app and format the USB drive with APFS or Mac OS Extended.

Step 4. Open the Terminal app and copy-and-past the following commands to make a booatble USB installer from macOS image:
For Majove: sudo /Applications/Install macOS Mojave.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
For High Serria: sudo /Applications/Install macOS High Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
For EI Capitan: sudo /Applications/Install OS X El Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/My

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