[Desire HD Q&A, Help & Troubleshooting] r.darwish:
First of all I would like to say this this is not the usual "How do i root?" question. I'm actually not looking for a HOWTO, but more for a detailed explanation about the process. I also wasn't sure if this thread should be posted in the developers or the general forums, so please move it to the general forum I you think it should be posted there.

I have an HTC Desire HD device, and I have seen countless tutorials about rooting, changing ROMs and changing other components which I actually don't know.

The problems with these tutorials:

1. They don't really explain what they are asking you to do. This actually may be convenient for most users, but I'm the kind of person that won't run any commands on his phone without actually realizing what they do.

2. These tutorials don't explain what can I do if something messes up.

I'm a programmer and I'm very familiar with Linux systems, but I am relatively new to Android. So after reading all sorts of tutorials, here are my questions:

About rooting in general

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1. How is obtaining root access in Android systems different from obtaining one in Unix systems?

2. Once I obtain root access, does that mean that all my applications runs as the root user? If so, isn't that a security risk?

3. Android have a different permissions system for applications than the classic Unix permissions system, since each applications must specify what does it want to do to the phone (Make phone calls, read the phone book, etc...), what happens to this permissions system once I obtain root access? Can any application use this root access to compromise my phone?

4. Is rooting my phone considered "hacking", or is it something legitimate like obtaining root access in a regular Unix system? Do all these rooting tools actually use exploits in the Android system to obtain root access?

Some questions about the downgrading process

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I read that in order to obtain root access on new HTC desire HD devices, I first my downgrade the phone's firmware. The questions below are based on the tutorial in addictivetips (I can't post a link since this is my first message)

1. Do I still have to do that, or maybe there's a new rooting method that doesn't require downgrading?

2. Once I downgrade and obtain root access, can I upgrade my ROM back to the new official ROM with root access, or does that mean that now I can only install custom ROMs?

3. Does downgrading the phone means I expose it to old security vulnerabilities?

4. My phone is branded. The tutorial suggest to prepare a "gold-card" by overwriting some bytes on the SD card, but none of them explained what does it mean. I would like to technically realize what does a gold card mean, and what does overwriting these specific bytes in the SD card mean.

5. What are the meaning of the commands that I should type before rebooting my phone in recovery mode?

Some HTC specifc questions

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The rooting tutorial says that after rooting I should obtain S-OFF, again, without really explaining what does it mean. As far as I realize, this is an HTC specific security mechanism.

1. What is it there for? Is it actually there to make my phone safer or is it there just to prevent me from changing my ROM?

2. I realized that there is S-OFF and Eng S-OFF, and the latter means gaining "Complete control" on my phone. What can I do with this "Complete control" that I can't do with normal S-OFF?

Using different ROMs

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1. I saw that there are some custom ROMs with HTC Sense. How is that possible? Isn't HTC Sense a proprietary HTC piece of software?

2. When I decide to use a specific ROM, how do can I make sure I have the latest Android version? Do I get automatic updates like when using the stock ROM, or is it my responsibility to always check if there's a new version?

If something messes up

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1. How can I go back to the stock ROM if the downgrading/rooting process messes up?

2. What can I do if a custom ROM installation messes up? Can I go back to the downgraded ROM?

Thank you