Windows Server 2012 R2 Boot Repair -

bcdedit /export C:\bcd_backup attrib C:\boot\bcd -s -h -r ren C:\boot\bcd bcd.old bootrec /rebuildbcd

Boot from a Windows Server 2012 R2 ISO or DVD. Select your language and click "Repair your computer" in the bottom-left corner. windows server 2012 r2 boot repair