What is Cydia? It's just like Installer, but it is open source and has more features. And more importantly, fewer problems to fix. If you'd like to learn more about Cydia, then check out the author's site here. Let me put out some critical information up front, before I get into the installation of this program.

* You can have Cydia and Installer both on the iPhone. This is not necessarily a replacement for Installer, but it could be.
* If you have already installed BSD Subsystem via the Installer, then it will be overwritten and a better version will be installed in its place via the Cydia program. You must never update BSD Subsystem via the Installer ever again as you could damage the installation files that Cydia will create.
* If you should use any programs from the Installer that require BSD Subsystem to run, then you should use the program called Fake BSD Subsystem which can be found in the System folder of the Installer.
* If you should use Cydia on an iPhone with applications and personal data already installed, and haven't used a program like BossTool to move them to the larger disk partition (where the bulk of your storage space is), then it will automatically move them for your freeing up space on the smaller partition.
* Once installed, you should occassionally refresh Cydia's repository to make sure you have current version of programs that you install.
* You can install Mobile Terminal and not have to install fix files for it or for BSD SubSystem like you do with Installer. Most importantly, you can change your master password to the iPhone! The Mobile Terminal will also not end your session until you logout of it, nice.

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