The connection to adb is down, and a severe error has occured.

最近做手机设置遇到了（Ubuntu 下）The connection to adb is down, and a severe error has occured

由于一直无法识别android 4.2 ，昨晚升级了adb ，今天出现了The connection to adb is down, and a severe error has occured该问题。解决办法是给adb 添加权限。

1.ll adb 

2. chmod a+x adb 

3.重启Eclipse，Clear 项目，就可以用了。