Symlinks

Credit
iPhone Dev Team

Exploit
Before the discovery of the LibTiff Exploit, this was used on 1.1.1 to jailbreak iPhones from 1.0.2. However, this only worked for iPhones, as the new iPod touch could not run 1.0.2 and therefore could not use this jailbreak method. The symlink method involved symlinking Filesystem:/private/var/root/Media, the "jailed" directory that could be accessed via iPHUC, to Filesystem:/, and then downloading, jailbreaking, and reuploading the entire system partition from.

This exploit was fixed in 1.1.2, when Apple introduced a check in the update ramdisk that prevented this from happening. Note that this is not the 1.1.2 mknod exploit.