Home Forums Mac Software Mac Operating Systems Which OS is downloaded in a clean install?

My Mac mini (Late 2012) shipped with Mountain Lion installed. I subsequently upgraded to Mavericks, and then Yosemite.

I took a look within my own Recovery Partition, and found BaseSystem.dmg. Mounting the disk image—OS X Base System—yielded, among other things, Install OS X Yosemite.app. The Base System also includes an Applications folder with Safari and a Utilities folder containing Disk Utility, Firmware Password Utility, Reset Password.app, Startup Disk.app, System Information, and Terminal. So it appears to be very much like the old install CDs as far as the presence of a compact OS is concerned.

I guess it depends what you mean by "has an OS installed." Any disk or disk image that can boot the computer technically qualifies. But the material to be installed—the full-fledged OS—is not on the Recovery Partition.