Suddenly I was not able to boot up Mac mini, got blank screen with " boot device not found" tried Command+r got in utility and repaired HD and found ok, but when restart again unable, with same error message
Mac mini, iOS 6.1.4
Try rebooting to the recovery drive again (Command-R at startup) and then go to the Startup Disk option in the Apple menu. If the boot drive is listed there, then select it and then try restarting.
If this does not work, then reboot the system again to the recovery tools and use the option there to reinstall OS X. This will take a bit of time to do, but will leave your personal files, applications, and data intact and only reinstall the operating system underneath it. This should get your system booting again.
Not able to boot up Mac mini
