The company bought a new Mac Air, needed to reinstall the system, and after consulting Apple support, they gave this scheme to try to install and succeed.
1. Please prepare an external hard drive formatted as a mac OS extension (journaled) to rename test.
2. On a computer with 10.10 systems, download it in the App Store and open the app to find the OS X Yosemite installation package.
3. Open the terminal.
4. Enter sudo/applications/install\ os\ x\ yosemite.app/contents/resources/createinstallmedia--volume/volumes/test in the terminal --applicationpath/applications/install\ os\ x\ Yosemite.app
5. Enter the administrator password at the prompt. Then enter y and press ENTER. Then wait for the production to finish.
Specific steps and formatting of the mobile disk reference: Http://www.iplaysoft.com/osx-yosemite-usb-install-drive.html
Making 10.10Yosemite External System installation disk