Hold down the “C” key as you start or restart. Once the disk has burned, test it by booting from it. Select the image on the list on the left-hand side and click Burn on the top menu: Once you have a disk image isolated and saved to disk: While you can save a tiny bit of space when saving Recovery Image by checking the compressed box, you don’t save that much space, and compressing it adds a little uncompressing time when unpacking it for burning. But it’s your choice. Of course, if you have one of the new Macs which has no Superdrive, you will need an external DVD/CD burner attached. Select the Recovery HD partition from the list, and click “New Disk Image” from the icons along the top: drive for macOS High Sierra, macOS Sierra, Mac OS X El Capitan, Yosemite. Now that you can see the Recovery HD partition, you can burn it to a disk. To install macOS or OS X from USB, you need to create a bootable install USB. Now in the list of partitions and drives, you should see a ghosted entry for “Recovery HD.” Burn it!
Next use the menu and go to “Debug -> Show every partition.”
Open Disk Utility again, and you will see the Debug menu is now showing between the Window and Help menus.
