This is dedicated to all of newbies :-
SO what is S-Off? :- S-OFF means that the NAND portion of the device which is unlocked and can be written. The default setting for HTC’s devices is S-ON, which means that neither can you access certain areas of the system nor can you guarantee a permanent root.
How Do I Know If My Device Is S-ON Or S-OFF? :- It is very easy to know just boot into HBOOT on your device, and the text on top will appear the flag status as either S-OFF or S-ON. A full root generally means S-OFF.
S-OFF – What And Why? :- HTC have installed a sort of security check whose level is determined by S-OFF/S-ON. Essentially, this security level is a flag stored on the device’s radio that checks signature images for any firmware before it is allowed to be written to system memory. This obstructs using any custom ROMs, splash images, recovery etc., and also restricts access to the NAND flash memory. However, when security level is set to S-OFF, the signature check is bypassed, allowing a user to upload custom firmware images, unsigned boot, recovery, splash and HBOOT images, as well as official firmware that has been modified.This enables maximum customization of your phone
(S-OFF also reduces restrictions on accessing the NAND flash memory on the device, allowing all partions to be mounted in write mode while the operating system is booted.)
How to get S-off on phone? :-
1.
Thanks to unrevoked tool as it is very easy to get S-off permanant on your phone. UNREVOKED is a painless root for HTC InCREDible and HTC EVO etc.
If you are looking for a simple root, visit http://unrevoked.com/m/ on your phone. Tap the logo to download the apk, install it and click Start. Your root is ready.
2.
To get root along with permanent security level S-OFF, visit this http://unrevoked.com/recovery/. Download and install the appropriate program for your operating system (Windows, Mac OS and Linux supported). Now, simply plug in your phone to PC via USB cable, and run the program that you installed – neat and simple.
Also you can consider visiting unrevoked team’s http://unrevoked.com/rootwiki/doku.php/public/forever that contains even more detailed instructions and explanation.
Main advantage of unrevoked forever :-
1.
The main advantage of using unrevoked forever is having S-OFF as the permanent security level flag. We know as HTC likes OTA updates, so having a permanent S-OFF means even if you flash an unrootable update, you can still flash a custom recovery and ROM, hence making your root permanent. You also cannot lose the ability to flash HBOOTs and radio images via FASTBOOT, which is again safer than using recovery.
2.
Unrevoked forever manages to get S-OFF permanent as it actually grants root access to the radio/NVRAM image instead of the traditional bootloader method. Hence, even if any update flashes a new bootloader, root access stays.
Helpful Sources --
Google
http://unrevoked.com/
Hope this is may be helpful