Finally this day has become and now you can download iOS 6 firmware here using direct links below for iPhone, iPad and iPod Touch and of course for iPhone 5. If you are interesting about unlock preservation you can use the link to find out possibilities to unlock iOS 6 using different methods. So read this first before iOS update because you may lose your unlock. it depends on what unlocking solution you choose for your iPhone.
Here a basic guide on how to install XPwn custom IPSW generator along with some of the other XPwn related projects. Note that they can be executed only on Debian based systems. One shouldn’t consider them as a substitution to GNU/Linux programming environment experience but we can assume this as a starting point. Just in case – XPwn is a command line materialization of planetbeing’s PwnageTool. It’s cross-platform and currently supported by Linux, Windows and Mac OS X.
Sendmodem is a tool that can access iPhone’s and iPad’s 3G baseband (modem) through /dev/tty.debug port without the need to disable the CommCenter. The original code for SendModem was taken from iPhone’s SMS app and its output format was slightly modified by sendmodem developer PmgRiPhone. Usually the modem or baseband is accessed through Minicom with sending commands to /dev/tty.baseband. Minicom needs CommCenter to be disabled in order to work normally. After you’re done using Minicom you have to enable the CommCenter again.