Just wanted to reiterate if you are wanting to backup DRM partition and unlock the xperia x, the post above (and the dirty cow post it links to) are pretty good, and worked for someone like me who is still novice in these areas. The DRM image was successfully created.

My curent noob question is now that i have my DRM img successfully backed up, i'm not sure from those threads how to actually restore it back to stock if i wanted to (i have only unlocked, not rooted).

Do you just copy the TA/DRM backup img file to phone and use twrp to flash it, or are you supposed to connect the phone to computer and boot into fastboot mode where you run adb commands from the pc? Have been searching but not found any explicit examples, just mentions of 'flash with the drm img back to stock'.