From iPhone Development Wiki
Use the following guidelines to avoid your package or app being fragile and to increase the chances of it being accepted by a community host.
Applications and Tweaks
- Avoid referring to /var/mobile directly - use NSHomeDirectory() if your code is running as mobile!
- If your code is running as root, use extra caution when writing files that mobile can access - you might break the file's access permissions.
- App Store apps will return their sandbox data path from NSHomeDirectory().
- See MobileSubstrate Pitfalls for additional guidelines regarding tweaks.
- You should consider the UDID deprecated like Apple has for some time, but if you need the device's UDID, use libMobileGestalt.dylib.
- If you need to use singletons, see singleton pattern for advice.
- If you need to respring from a tweak and you are targeting iOS 6+, kill backboardd instead of SpringBoard. Killing SpringBoard has been known to cause some issues regarding the backlight.
- Do not create mobile-owned files and/or directories in your package. Stay out of mobile's home directory!
- All package files are installed as root. Your software should create any required files or directories at runtime.
- This is doubly important for preferences. A user's preferences do not belong in a package: if preferences are stored in the package, they will be overwritten when you release an update, and deleted when the user uninstalls your software (even temporarily!)
- Do not use postinst/preinst/extrainst_ for file management purposes!
- Do not store in the package files or directories that your software could create.
- Do not enforce permissions that your package should contain. dpkg uses an expressive packaging format that has support for permissions, ownership, and links. Use that support!
- Make sure your package doesn't include hidden .DS_Store, ._*, or thumbs.db files.
export COPYFILE_DISABLE=1will disable resource forks (._* files) being included on OS X.