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S-OFF explained - by a Developer

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Lately I have read many posts with wrong assumptions about S-OFF. I am writing this post in General to clear up to many of you what S-OFF is and isn't.

To start off, S-OFF has nothing to do with your phone being rooted. I've seen people post that S-OFF means a "full" root, or "permanent" root. Those terms aren't even correct, root is just another user on the linux system, and you either have access to it or you don't. Rooting your phone and what that entails is out of the scope of this writeup.

When your device is shipped, your bootloader will show the flag S-ON. This stands for Security-On. What this security does is protect the NAND partitions (ie: the boot partition, the recovery partition, the radio, the system partition...) from being permanently modified at all. Basically, all changes made to these partitions while the phone is running is not permanent, and will be reset upon a reboot. Also, while your phone is S-ON, all firmware zips (ie: PJ75IMG.zip) must be digitally signed by HTC in order to be flashed through the bootloader.

When your device is set to S-OFF, the security is turned off. This allows you to modify any partition on the device, and changes will not be reset upon a reboot. Also, the signature checking of the firmware zips (ie: PJ75IMG.zip) is disabled, allowing users to flash unsigned firmware zips containing the separate images of the partitions. S-OFF gives the user great power over the device, but also comes with much responsibility to be careful.

I have seen many posts stating the term "S-OFF root". As I stated earlier, S-OFF and root are completely different things. When you have S-OFF in the bootloader, you then can flash a package containing Superuser.apk and the su binary, which in turn will give you root in the file system when the device is booted. Again, S-OFF does not mean you have root. You can have S-OFF set (if there was an S-OFF exploit released) on the stock phone running the stock unchanged ROM, and not have root in the file system because you haven't pushed/flashed the Superuser.apk and su binaries on your phone yet.

I have also seen many posts about people not "trusting" the bootloader unlock at HTCdev. Yes, we all know that it does not set the bootloader to S-OFF, but it does unlock the partitions that are needed to flash a custom recovery, and through that flash a custom ROM. This is probably the most trustworthy way to "unlock" the bootloader. Any S-OFF method released here in the future will most likely be a hack to make it work. Imagine if HTC gave out the radio S-OFF unlock. That would mean ANYONE (specifically people who are very flash happy) could find a random radio firmware zip which.. oops.. isn't for the correct device, flash it through the S-OFF bootloader, and brick their device. Releasing the limited unlocking was very smart by HTC, and will definitely save many phones from ending up in the graveyard.

Now I am not saying I do not want S-OFF haha. As a developer, S-OFF is well needed and is extremely useful. It's definitely being worked on. But for the average flasher, (of ROMs, not human parts ) radio S-OFF is not needed.

Hope this clears up confusion about what S-ON and S-OFF is. I will add to this as I feel necessary, and to clear up some of my sentences (Sometimes I start typing before I finish thinking of what I'm going to type).
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30th May 2012, 01:48 AM |#2  
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Thank you.
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30th May 2012, 01:50 AM |#3  
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Thank you soooo much haha so many people were confused about it...

A good example is my moms phone. She has an evo 3d and I made it s-off with eng hboot in case I sell it at a later time. Currently it's not rooted at all, but if I want to considering my bootloader's unlocked I could easily flash a recovery and then flash superuser which in turn gives me root
30th May 2012, 01:51 AM |#4  
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make the subject a bit more clearer
cuz when i saw it i thought that you had s-off for us lol
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30th May 2012, 01:56 AM |#5  
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please sticky this!
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30th May 2012, 02:00 AM |#6  
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If I may add to this discussion ...

If you do not already know these terms and what they mean you should probably not be attempting to root your phone yet

You should instead invest some time reading and learning first.
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30th May 2012, 02:20 AM |#7  
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Quote:
Originally Posted by Unreasnbl

If I may add to this discussion ...

If you do not already know these terms and what they mean you should probably not be attempting to root your phone yet

You should instead invest some time reading and learning first.

Or, rather, you should not be attempting to gain access to the root user / superuser account and privileges on your phone.
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30th May 2012, 02:25 AM |#8  
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Updated the title just for clarity. If there's anything someone disagrees with or would like to add to the OP, let me know here and I'll see what I can do. And I definitely agree with Unreasnbl. It may be a pain in the a$$ to read before jumping into things, but seriously, it will help so much when it comes understanding.
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30th May 2012, 02:42 AM |#9  
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Quote:
Originally Posted by Unreasnbl

If I may add to this discussion ...

If you do not already know these terms and what they mean you should probably not be attempting to root your phone yet

You should instead invest some time reading and learning first.

I rooted, with S-off, and flashed my phone before I understood any of these terms lol. Just by following instructions clearly.

But then later I learned all of these things.


But yes, you are absolutely correct.



edit: this is a good, valuable post op. Thank you.
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30th May 2012, 02:49 AM |#10  
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Quote:
Originally Posted by arozer

I rooted, with S-off, and flashed my phone before I understood any of these terms lol. Just by following instructions clearly.

But then later I learned all of these things.


But yes, you are absolutely correct.



edit: this is a good, valuable post op. Thank you.

I think you just prooved the OP correct, you shouldn't have S-OFF, because it doesn't exist yet and you don't need it and that's probably good for person that thinks they rooted with S-off.
30th May 2012, 02:50 AM |#11  
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Smile Thank you
Thank you for the great info! While not a noob(have had rooted, s-off OG 4G, and 3D, just rooted EVO LTE), I don't understand, nor want to, at an advanced level, Linux, ADB,FASTBOOT, etc. I like making my phone my own, and like flashing ROM's. I tried to use the HTC method of unlocking, but am just not comfortable with my skills to try and use SDK/ADB/FASTBOOT. Perhaps I can find someone in San Antonio to show me, but unless/until, I'll wait for someone such as yourself to provide a "dumbed-down" method. Again, thanks for sharing your knowledge and expertise.

Update: Couldn't stand it..went ahead, carefully reading and following instructions, and did HTC unlock. Had a few issues with TWRP, and flashing ViperROM, due to internal/sd configuration, but moved things to their proper place with ROM toolbox. Everything in it's place, and my phone running like I like it for almost 24 hours with no issues, other than the hilarious HTC warning at boot screen.
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