AT&T Samsung Galaxy S III – How to root and install a custom ROM

This post describes how you can take an AT&T Samsung Galaxy S3 (SGH-i747), and configure it with a custom ROM. 

imageWhy would you want to do this?  For me, the biggest reasons are to gain access to the native tethering (hotspot) features that Android has, but the carrier disables.  Most custom ROMs also completely remove carrier bloatware, and add some nice features, such as custom toggle buttons, themes, and the ability to increase battery life or improve performance. 

It can be fun to try out different ROMs, to see what your phone is really capable of.  Some people get bored with their phones, and want to try new ROMs all the time.  These people are called “flashaholics”.  This guide isn’t for flashaholics, and it isn’t for people who have never rooted before.  This is intended for people who have rooted and/or flashed ROMs before, and are looking for a simple set of steps to configure an SGS3. 

I will further assume that you’re looking for a very stable replacement for the stock ROM, you want to preserve some of the Samsung “special sauce”, with enhanced capabilities and great battery life.  For the SGS3 – I believe that Intergalactic V3.0 meets these criteria.  So this set of steps will focus on how taking a stock SGS3 and doing only the necessary steps to install this great ROM. 

This process is adapted from a great tutorial by Rastabolino on XDA.  You can see the original thread here.  If you run into problems or have questions about the overall process, this is the best place to start.

DISCLAIMER:  you can mess up your phone if you don’t know what you’re doing.  You are responsible for any problems or damage to your phone – do this at your own risk!

The steps are as follows:

  1. Backup anything you want to save (pictures, text messages, phone history, etc.)
  2. Get Root Access
  3. Install a custom recovery
  4. Download and flash a custom ROM
  5. Enable

More details on each step below:

Step 1:   Backup pictures, text messages, phone call history, etc.

To backup your pictures, connect your phone to a computer, go to your File Explorer, Select your phone, browse to the DCIM folder, and copy all of the images inside.   If your phone isn’t recognized, you can install the Samsung USB drivers here.

To backup text message and call history, install an app called SMS Backup +, and follow the instructions. 

Step 2:  Get Root Access

First, install the Samsung ODIN utility.  Download and install it from here.  If you have Kies installed, make sure it is closed and kill the background process using task manager.  Or just install it. 

Next, download a rooted version of the stock ROM from this thread on XDA.  Make sure you select the correct image (e.g., i747 if you’re using AT&T).  The downloaded file will be very large (>500MB). 

Unzip the image using 7-Zip.  If you don’t have this utility, download it here

Follow these steps to put your phone into download mode:

  1. Unplug the USB cable.
  2. Shut down the phone.
  3. Hold down the ‘HOME’ + ‘VOLUME DOWN’ buttons and press the ‘POWER’ button for about 2 seconds until a WARNING! Screen appears. Press the ‘VOLUME UP’ button to enter Download Mode.

Start Odin, connect your phone to your PC, you should see the box under ID:COM change color to show your device is connected. click on PDA and select the .tar file you just extracted. Caution:  DO NOT TOUCH THE CHECKBOXES!  Specifically, DO NOT TOUCH THE RE-PARTITION CHECKBOX!!!!

Hit the start button and wait for the file to flash to your phone.  It will take 10 minutes or more to complete flashing.  Do not be concerned, and DO NOT remove the USB cable while the phone is flashing.  When done your phone will reboot automatically.   

Step 3:  Install a custom recovery

OK, now you are rooted!  Next step, go to the play store and download a program called GooManager.   Launch it – it will request SuperUser permissions, say yes. 

Press your Menu button (bottom left), and choose “Install OpenRecoveryScript”, and confirm by selecting Yes.   GooManager will download and install TWRP recovery on your phone, which will allow you to easily install custom ROMs. 

Step 4:  Download and flash a custom ROM

Now, back in GooManager, select the top option:  “Browse Compatible ROMs”.  Scroll down to “stratatak7” (this is the developer for the Intergalactic ROM).  Select “Intergalactic 3.0”, then “Begin Download”. 

If everything’s working okay, your download should start after a 10 second pause.  But sometimes the servers that GooManager uses seem to be overloaded.  If you don’t see anything happening, or if it’s too slow, you can download directly from stratatak’s Intergalactic XDA thread

If you manually downloaded it on your PC, connect your phone via USB, open your file explorer, and copy the ROM zip file to the phone.  The “Download” folder is a good location, but it doesn’t really matter.  This will take a while. 

When the ROM file has finished transferring, unplug the USB cable and reboot your phone to Recovery mode.  The easiest way to do this is go back to GooManager, and select the Menu button (bottom left), and select “Reboot Recovery”.   Alternately, you can shut down the phone, then hold HOME + VOLUME_UP while you press the power button for about 5 seconds. 

Once you’re in TWRP recovery perform the following steps:

  1. Do a factory reset (select Wipe, then swipe at the bottom to perform a Factory Reset)
  2. Wipe cache and dalvik cache (select “Back”, then go to Advanced Wipe, check the boxes for Dalvik Cache and cache, and then Swipe to wipe)
  3. Wipe system (select “Back”, check the box for System, and then Swipe to wipe)
  4. Flash Rom (select “Back”, hit the curled Back arrow at the bottom right twice, select Install, locate and select the Intergalactic 3.0 zip file, then Swipe to confirm flash.  This will take a few minutes)
  5. Wipe cache and dalvik cache again just to be safe (select the Wipe cache/dalvik button)
  6. Reboot (hit Back and Reboot System).  If you are prompted to allow TWRP to fix SuperSU permissions, go ahead and do it. 

Your first boot will take quite a while, don’t be alarmed.  Enjoy the ROM!  If you are so inclined, head over to stratatak’s XDA thread and use the “Donate to me” button to buy him a beer. 

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