Just unboxed some new MBAs for my business users who were due for an upgrade, and plugged in my Mavericks bootable USB installer to them, but was greeted with a gray prohibitory sign. I also tried the Yosemite installer just to see if I could boot from anything and got the same thing. I know the drive works because I wiped another separate, older MBP earlier today with it and was successful. I have never had trouble alt-key booting into the USB drive before on the previous model MBAs. Has something changed with the latest and greatest MBA?
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Prohibit Sign on USB Installer - New Model Air (2015)
- Thread starter boostercb
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Yeah, you are definitely not going to be able to install Mavericks on the new machines. Like the previous poster said, you generally can only install the version of OS X that is most current at the time of release. Right now that is 10.10.2, but even 10.10.2 was released before these machines were, which means the generic 10.10.2 installer from the App Store doesn't have all of the drivers for the newest machines included within it. Apple produces a special build of the latest OS for new machines that include those drivers. For the Early 2015 Airs, that special build of OS X is 10.10.2 build #14C2507, in contrast to the build # of the current widely-available general release version of 10.10.2 which is 14C109 (14C1514 after all available security updates are applied).
You can use Internet Recovery on your new 2015 Airs to download and reinstall 10.10.2 14C2507 to them, or you can wait until the next version of OS X is released, which will be 10.10.3, and will be the first general release of 10.10 to support all Macs manufactured to-date, including these new machines. Then you can make a new USB installer from 10.10.3 which will work on the new Airs.
-- Nathan
