Image via Before You Start The obvious first step here is to. But before you do anything else, a word of caution: once you've used the OS X installer, it will automatically delete the file you need to make the backup disk, so you'll want to either make a copy of the installer or create your disk before you upgrade. You can use a USB flash drive, external hard drive, or DVD-R disc, but the USB drive is quicker. If you're using a USB drive, it has to be formatted as 'Mac OS Extended (Journaled)' and set to partition type 'GUID Partition Table' in order to work. Image via Once inside, browse to the ' Contents >SharedSupport' folder where there will be a file called ' InstallESD.dmg. Echolink Satellite Receiver Software Download. Nikkormat Ft Serial Numbers. ' This is the image file that contains the information you need to create the backup disk.