There are several different ways to install macOS Catalina (for pre T2 chip Apple computers), better known as macOS 10.15. One of best ways is to install via a USB stick. You don’t need to buy a special USB stick nor do you have to purchase a special program to make an macOS 10.15 Catalina USB Install Stick.
Create a USB Install Stick
Create a USB Install Stick for macOS 10.15 Catalina with these four easy steps:
- Ensure that you have the Install macOS Catalina.app installer application in your Applications folder. If you don’t have it, you can download it from the App Store. You will need to look in the Purchased tab and click Download for macOS 10.15 Catalina
- You will need plugin a 8GB or larger USB stick, preferably a USB 3.0 stick. This USB stick will be erased of all data. A faster USB stick will help speed up this step as well as decreasing the time that it will take for macOS 10.15 Catalina to install.
- Open up Terminal, located in the Utilities folder, which is located in the Applications folder.
- Run the follow command as listed below:
sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/partitionToEraseOnUSB
Now you can Quit Terminal and Eject your USB stick. You now have a fully function macOS 10.15 Catalina USB Stick.
Once you have created your macOS Catalina USB stick, restart the Mac computer that you would like to erase and reformat.
After you turn on the computer, hold down the Option key. You should now be able to select the drive that you would like to boot from. Select your newly create macOS Catalina USB stick. After a few minutes, you will now be able to use Disk Utility to Erase your internal SSD or hard drive and then re-install macOS Catalina.
If you need more details, please check out the macOS 10.15 Catalina bootable installer page from Apple