Creating a bootable USB drive in Mac OS X or macOS is very useful when it comes to reinstalling the operating system after a problem with the hard drive. You can also use the system tools without them being launched from one of the partitions of the disk, or even install the complete system on a machine without internet access.
Create a bootable installer for macOS is a straightforward process, but still requires a little time and patience. You can install the operating system of your Mac using an external drive (USB flash drive, external hard drive) or secondary volume as the startup drive. On the other hand, know that it is not necessary create a bootable installer if you just want to reinstall macOS or reset your Mac to factory condition (to sell it, for example).
The items required to create a bootable macOS USB drive
- 1 USB key or other secondary volume, in Mac OS Extended format, with at least 12 GB of available storage
- The installer downloaded for macOS Big Sur, macOS Catalina, macOS Mojave, or macOS High Sierra
- About 30 minutes to 2 hours of your time
Two software to simplify your life (excluding macOS Big Sur)
There are two easy-to-use software for creating bootable macOS USB drives: DiskMaker X and Keylifornia. These two software will take care of doing the work for you and we strongly recommend that you follow their tutorials. On the other hand and if you wish create a bootable USB drive for macOS Big Sur, these software are not, at the time of this writing, by still compatible with this version of the system. Remember to check their respective sites, things may have changed by then. If it still isn’t, don’t panic, here’s how to do it manually on macOS Big Sur.
Create a bootable USB (for macOS Big Sur specifically)
- Download the installer for macOS Big Sur
- Connect your USB stick
- Open the app Terminal
- Type the following command line:
sudo /Applications/Install macOS Big Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/nomdevotrecléUSB
- Press on Entrance
- Enter your session password (it will not be displayed but this is normal)
- Press the touch Y
- Accept, then wait.
Booting your bootable USB drive (for macOS Big Sur specifically)
- On Mac Intel, hold down the Option (⌥) key while your Mac is starting up and select Install macOS Big Sur
- On Mac Apple Silicon, hold down the Touch ID key when starting your Mac and also select Install macOS Big Sur
- In both cases, then follow the installer.
How to create a bootable USB drive with a macOS install partition (excluding macOS Big Sur)
First of all, you will need to have a USB key, SD card or any other empty medium with at least 12 GB of free space, and download the installer for your operating system again. It comes in the form of a seemingly all-classic app. However, it has the particularity of self-destructing once the installation program is finished.
- Press and hold the key alt or Option (⌥), then click Purchases at the top of the window
- You can also enter the name of the system directly in the search box (macOS Mojave for example)
- You should find in the list your current operating system and also other versions of macOS that you had previously installed
- Choose the version that suits you then click either on Download, be sure cloud icon
While the system installer application is downloading, we will format the USB drive.
- Open the app Disk Utility
- Plug in your USB key, and select it
- In the right area, go to the tab Partition
- In Partition scheme choose 1 partition
- In Partition Information choose boot as name (this allows us to give you a ready-made copy / paste command), in format choose Mac OS Extended (Journaled)
- Click on Options…, select GUID Partition Table, then click okay
- Click on Partition
Now, we’re going to use a command line utility – included in the macOS installer package since version 10.7 – that greatly simplifies the creation of a bootable USB drive. The command in question depends on the operating system you downloaded.
- Open the app Terminal using Spotlight for example
Copy the command corresponding to the operating system you downloaded:
macOS High Sierra
sudo /Applications/Install macOS High Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
sudo /Applications/Install macOS Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install macOS Sierra.app
macOS El Capitan
sudo /Applications/Install OS X El Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/boot --applicationpath /Applications/Install OS X El Capitan.app --nointeraction
sudo /Applications/Install OS X Yosemite.app/Contents/Resources/createinstallmedia --volume /Volumes/boot --applicationpath /Applications/Install OS X Yosemite.app --nointeraction
sudo /Applications/Install OS X Mavericks.app/Contents/Resources/createinstallmedia --volume /Volumes/boot --applicationpath /Applications/Install OS X Mavericks.app --nointeraction
You will be prompted for a password – enter your session password then hit Enter
The operating system is being transferred. This may take up to 20 minutes depending on the media to which the system is transferred. Be patient. Your terminal window should look like this when finished:
If during this time you want to know where the process is, you can go to the Activity monitor (accessible via Spotlight), go to the tab Disk click at the top of the column Operation name and find the process createinstallmedia. In the column Burned bytes you can follow the progress (the complete image is about 5.5 GB).
Boot the installation of macOS from your USB key
To boot the installation of macOS from your USB key, there are two methods. One assumes that you still have access to your system on your hard drive, the other works in all other cases.
- Plug in your bootable USB stick
- Go to the menu at the top left of your screen, then in System Preferences …
- Go to Boot disk
- Select Install OS X [nom du système] then click on To restart…
When the computer starts
- Computer off, plug in your bootable USB drive
- Turn on the computer and immediately press the alt orOption (⌥)
- Choose the volume whose name begins with Install OS X.
- That’s it !