因修改usb驱动一部分文件，致mac book pro重启后，键盘，usb等外设全部失效，然后不停的google，重要找到方法了 在按启动的时候：按住command + R 就可恢复系统， 本以为会导致数据丢失，但是发现有重装系统的的选项，这样就安心多了。 http://support.apple.com/kb/ht1533 Keystroke Description Press C during startup Start up from a bootable CD, DVD, or USB thumb drive (such as OS X install media). Press D during startup Start up in Apple Hardware Test (AHT). Press Option-Command-P-R until you hear startup sound a second time. Reset NVRAM Press Option during startup Start up in Startup Manager, where you can select an OS X volume or network volume to start from.   Press Eject, F12, or hold the mouse or trackpad button Ejects any removable media, such as an optical disc. Press N during startup Attempt to start up from a compatible network server (NetBoot). Press T during startup Start up in Target Disk Mode. Press Shift during startup Start up in Safe Boot mode and temporarily disable login items. Press Command-V during startup Start up in Verbose mode. Press Command-S during startup Start up in Single-User mode. Press Option-N during startup Start from a NetBoot server using the default boot image. Press Command-R during startup Start from the OS X Recovery System1