dual-boot your iPhone!

Brought to you by NerveGas, planetbeing, ghost_000, dinopio, bgm, MuscleNerd
and the combined iPhone-Elite and iPhone/iTouch Dev teams.

OVERVIEW (by NerveGas)

The dev team has been using dual-booting to jailbreak the iPhone for several months now, however now that several more advanced techniques have been developed (many of which are still private), I thought it apropos to release this cool hack for those who would like to dual boot multiple versions of the iPhone software (or other OS's) from their handset. It's a neat little hack that I think might be useful for developers playing with 1.2.

I'll walk you through a sample jailbreak scenario with 1.1.4, using 1.1.1, to show you what I mean. To do this, you will carve out a new partition on the iPhone and install version 1.1.1 on it. You'll then upgrade the iPhone to v1.1.4, which will leave the new partition intact. You can then dual-boot the iPhone, allowing you to mount 1.1.4's partition using the 1.1.1 partition. Once mounted, you'll make some changes to the mount points and install OpenSSH.
Once you've got two versions of the OS functional, you can easily switch between them by changing your root-device. For example:

nvram boot-args="rd=disk0s3 -v"
tag:iphone, jailbreak, iPhone unlock, Oktoprep, jailbreak.jar,