AFC

AFC
AFC (Apple File Conduit) is a service that runs on every iPhone / iPod, which iTunes uses to exchange files with the device. It is jailed to the directory /private/var/mobile/Media, which is on the second (non-OS) partition. The AFC service is handled by /usr/libexec/afcd, and runs over the usbmux protocol.

AFC2
AFC2 is an additional AFC service, configured to allow access to the whole filesystem. Installing it and patching the fstab file for full write access is considered a bare-bones jailbreak. Up to iOS 7, the AFC2 service is added by editing the /System/Library/Lockdown/Services.plist file and adding a service that runs under root with access to the /|root filesystem. As of iOS 8, services list with root access permission is hardcoded inside lockdownd. There is a function that the list data inside lockdownd (CFPropertyListCreateWithData involved) and we still could use Mobile Substrate to hook the function to add AFC2 service to the list.