Most tools help users and developer add things to their Andorid devices—be it themes, mods, or even GUI interfaces that flash kernels and ROMs. However, there’s another genre of tool that is just as essential to the Android experience: applications that backup essential system files that can easily be broken when flashing development work.
XDA Senior Member HellcatDroid created one such tool for Samsung Galaxy S II, allowing users to perform numerous tasks including backing up and restoring EFS, dumping the kernel, flashing kernels, and verifying that your EFS partition is intact. The tool has been out for awhile, and most of the bugs have been worked out.
For additional information, screen shots, a full change log and feature list, check out the utility thread. Now before anything goes awry, backup your EFS partition. If it’s too late for your device, and you have already borked your EFS and IMEI, you’ll need a more manual method.