I'm leaving this post here for posterity's sake, but an easier root method is now available at:
The package may be downloaded at http://vulnfactory.org/public/motochopper.zip
As promised, this post describes how to root the Atrix HD Jelly Bean build. This should also work on other Motorola 4.1.2 builds (Razr/Razr Maxx, Razr HD, Razr M, etc.).
The exploit requires setting up a special Samba share and mounting this share on your phone using the File Manager app. I apologize that this process may seem involved for some of you, and request that members of this community help each other out if some of you are having problems completing the procedure. I'm not able to provide individual tech support to every user who wants to root this phone.
The following instructions require a working Linux installation. The following instructions are for Ubuntu. If you don't want to install Ubuntu permanently on your machine, I suggest using a LiveCD installation. Instructions on setting this up are described here:
Once you're booted into Ubuntu, open a terminal. Create a new directory for your Samba share:
sudo apt-get install samba
sudo gedit /etc/samba/smb.conf
[share] path = /tmp/share available = yes valid users = guest read only = yes browsable = yes public = yes
Next, create a user for the Samba share by typing in the terminal:
sudo useradd guest -m -G users
sudo passwd guest
Next, set a password on the share. Use the same password you just provided:
sudo smbpasswd -a guest
Next, restart the Samba server:
sudo restart smbd
cd /tmp/share wget http://vulnfactory.org/public/motoshare.tgz tar xvf motoshare.tgz sudo chown root:root pwn sudo chmod 6755 pwn
Next, move over to your Android device. Ensure you have enabled USB Debugging Mode (under Settings -> Development Settings). Ensure your device is connected via Wifi.
Open the "File Manager" app, and select "Remote storage". Click "Add storage", and fill in fields as follows:
Host IP address: [your Linux machine's IP address] Domain name: WORKGROUP Shared folder name: share User: guest Password: [the password you created above]
sudo /tmp/share/adb kill-server sudo /tmp/share/adb shell /storage/rfs0/pwn
Finally, install Supersu by typing the following in the terminal:
sudo /tmp/share/adb install /tmp/share/eu.chainfire.supersu.apk
I can't stress this enough: I can't provide individualized tech support for everyone on this forum. Please help each other.
TTLayland has been successfully rooted using this technique and has volunteered to help. If you get stuck and can't find support on these forums, feel free to email him at ttlayland (at) gmail (dot) com.