Step-by-step

Create a boot drive

1 Open Disk Utility

Connect your USB drive to your Mac and wait for it to mount. Now go to your Applications folder (or use Launchpad) and open the Disk Utility app to get started.

2 Find your drive

In Disk Utility, select your connected USB drive from the ‘External’ section of the sidebar and then click on the ‘Erase’ button in the top row of the interface.

3 Format the drive

From the dropdown menu next to the Format heading, select ‘Mac OS Extended (Journaled)’. This will format the drive in a way that it can be read and written to by your Mac.

4 Name your drive

Give your boot drive a name. What you call it will need to be entered at the end of the Terminal command in step 8, we went for ‘Catalinabootdisk’. Click on ‘Erase’ again.

5 Erase the drive

Your USB drive will now be erased and set up as new. Now eject the disk and then mount it again to ensure that it works OK with your Mac. You’re now good to proceed.

6 Download installer

Now go to the App Store and search for ‘Catalina’ to locate the macos Catalina installer. Download it and when the installer launches, press Cmd+q to quit it.

7 Launch Terminal

The Install macos Catalina app will now be in your Applications folder. Double-check and while you are there, launch your Mac’s Terminal app. Now things get a little tricky.

8 Enter the command

In Terminal, type the following command: sudo /Applications/install\ macos/ Catalina. app/contents/resources/createinstallmedia --volume /Volumes/[name of your disk].

9 Keep it safe

Press Enter after entering the command and when Terminal informs you that the installation has finished you can eject the USB drive. Store it safely for times of need.