Basic understandings of iPhone/iPad

1/ iOS is unix-based operating system - debian/ubuntu? so that's reason why there are some workforce to port iPhone GCC compiler to Ubuntu - https://github.com/javacom/toolchain4#readme - need study, confirmed?
- So please do remember some constraints related to security matters, eg: you ssh (using root) a file to iPhone and then your application (default using 'mobile' user) to access that file - it'll be failed due to security

2/ IPA package is generally zip file with content inside

3/ Some important folders/directories in iOS
- Default user-home folder: /private/var/mobile
- User-home Application folder: /private/var/mobile/Applications - This is where all the real application code, data stored - so if you want to hack your application - come in here
- User's application data: /private/var/mobile/Documents/ - This is where you see your working data in application stored
- Default iPhone Application folder:  /var/stash/Applications
TBC

4/ Package in iOS
- deb file: is a traditional debian package file so you can use debian command to install, remove it, eg: dpkg -i

- ipa file

5/ Default root password: alpine