Tethered jailbreaking is something that some (many) of you only find out when Blackra1n was released. The tethered jailbreak is quite inconvenient since, every time you restart the device, you find yourself with an original iDevice! Cydia suddenly disappears and with it, all installed applications.
Apple has started shipping devices with bootroms not vulnerable to previous exploits. So far, these devices include at least the iPod touch 3G. They also likely include the new 8GB iPod touch 2G and very recent versions of the iPhone 3GS. For these devices, even though an iBoot exploit can make your filesystem jailbroken, the device itself is not bootable after that point without being “tethered” to something like a computer.
While requiring a computer, DEFCON badge, or TI-84 calculator to assist an iPod boot is mostly just an inconvenience, requiring the same thing for an iPhone reboot is a major hassle. It means you won’t be able to use your iPhone as a cellphone until you can perform the tethered boot. Every time your battery runs out or your system resets due to a software bug or memory exhaustion, you’d need to do a tethered boot to use your phone again.In order to overcome this obstacle on these very recent devices, a new bootrom exploit will need to be found.
Previous tethered jailbreaks