Earlier this morning we announced the update of the Droid RAZR M Utility which includes a 4.1.2 FXZ file. You may be one of those who prefers to do thing manually without the assistance of a Toolkit. It is also much quicker sometimes to do things manually since you aren't having to wait on a utility that is full of things you don't actually need to download. @P3Droid tweeted out a 4.1.2 Fastboot file that is prerooted with busybox installed! You would simply flash this file in RSDLite! Pretty simple stuff! You can grab the file from the link below!
Via @P3Droid