A bootable MacOS installer can help you in many situations. So, if you want to know how to make a bootable MacOS installer on a flash drive, this is the guide for you.
Having a bootable MacOS installer can act as an emergency disk when your Mac experiences some trouble and you are unable to access recovery mode or if you want to do a clean install of MacOS.
It can also come in handy if you have multiple Macs that need new MacOS to be installed, then why bother downloading the MacOS to all the Macs when you can use one bootable flash drive to install MacOS on them all.
There are several reasons why you may want to create a bootable USB flash drive for MacOS. But, there are only two ways to create a bootable MacOS Mojave USB flash drive.
The first method involves downloading of MacOS from the iTunes and using the Disk Creator tool. The second method also requires you to download the MacOS installer and then use the terminal command to create a bootable flash drive instead of using the Disk creator tool.
Both of these methods apply to all the versions of MacOS including the MacOS Mojave, High Sierra, and Sierra.
To be able to create bootable MacOS flash drive you need at least 12 GB of storage. Earlier the requirement was 8GB, but now Apple recommends a USB flash drive with at least 12 GB of storage. If you don’t have 12 GB flash drive, use the 8 GB flash drive.
Make sure you take the complete backup of the data in the USB flash drive as the drive will be formatted and any data in it will be erased during the process.
You need to download your preferred MacOS installer from the official website. The link to download MacOS Sierra and MacOS Mojave (beta) are given below.
Download MacOS Installer
To be able to create MacOS bootable flash drive you need MacOS installer. You can download the installer from the Mac App Store on your Mac.
Download MacOS Sierra / Mojave from the Mac App Store. Launch Mac App Store and search for High Sierra or Mojave. If you have previously installed any of these MacOS then you can find them under Purchased tab.
Click the Download button. When the pop-up says you have already installed the downloading version of MacOS, click Continue. This will begin the download of the full installer.
Depending on the internet speed, the installer might take few minutes to a few hours to download.
The installer may self-launch after completing the download. Click Quit to close it. Proceeding any further will delete the Installer, so simply click Quit to close the installer.
Download Mojave Beta Installer
MacOS Mojave is still in beta and may take a little while before it is available for public release. If you want to install the beta version of MacOS Mojave then here is how to get the installer.
Sign up as a developer on Apple website or for the public beta program. After that, you need to download MacOS Mojave Beta Access Utility and then download Mojave Installer from the Mac App Store. Don’t run the installer by yourself. If the installer auto-initiates the installation close it.
Create Bootable Flash Drive using Disk Creator
Creating a bootable flash drive using the Disk Creator tool is the easiest and the safest way to create a bootable MacOS USB flash drive with a free utility, Disk Creator.
Begin with downloading Disk Creator on your Mac. Get it from here.
Insert the 12GB ( or 8GB) flash drive. Make sure you have taken the backup of any data in the flash drive.
Launch Disk Creator on Mac and click “Select the OS X Installer” button.
Look for the downloaded MacOS Mojave / High Sierra installer and select it. You can find the downloaded installer in the Application folder.
Select the inserted flash drive from the drop-down menu in Disk Creator utility.
Click “Create Installer” to begin the process.
The Disk creator utility will now process the file and create bootable flash drive out of the MacOS installer.
The newly created MacOS bootable flash drive can be used to install MacOS on any Mac. Simply insert the bootable flash drive and boot up your computer while holding the Option key.
Proceed with the on-screen instructions to install MacOS from the bootable flash drive on the Mac. You can use the Flash drive on any number of macs, and there is no limit to it.
Create Bootable Flash Drive using Terminal Command
Insert the 12 GB ( 8 GB) flash drive into the Mac. You may want to give the flash drive a name, let’s call it as USB for this tutorial.
Format the USB flash drive for OS X Extended (journaled). To do this, open Disk Utility.
For those using High Sierra, click the View drop-down button and select “Show All Devices“.
Select the Root drive in the sidebar and click on Erase.
Select Mac OS Extended (Journaled) as the Format and GUID Map as Scheme. Also give your flash drive a name, USB or anything you like, but remember it.
Click “Erase” to format the flash drive. Click “Done” once the formatting is complete.
Open the Terminal by navigating to Applications > Utilities.
Copy and paste the following command in the terminal window.
You need to replace USB ( in the below command) with the name of your flash drive. If you have named it as USB while formatting then paste the command as it is. The command has slight changes for the different version of MacOS, so copy the right command for the right version of MacOS.
Command for High Sierra
sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/USB --applicationpath /Applications/Install\ macOS\ High\Sierra.app
Command for Mojave
sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/USB --applicationpath /Applications/Install\ macOS\ Mojave.app
Press “Y” and hit enter to proceed and ignore the warning message. Wait for the terminal to copy installer files to the disk and create a bootable flash drive.
Once the macOS USB flash drive is ready, you can insert the disk into any Mac and start the Mac while holding the Alt\Option key.
That’s it. You have successfully created a MacOS bootable flash drive. You can format the USB flash drive after installing MacOS and use it to keep the files and data. However, if you can afford to keep a spare USB flash drive, then I would recommend you to keep the bootable flash drive as it is as it may come in handy if something goes with your Mac in future or if you need to perform a clean install.