iPhone Dev-Team has released RedSn0w 0.9.8b4 for developers to jailbreak iOS 5 Beta 4 and it is a tethered jailbreak, which means that you need to connect your iOS device to the computer on every reboot…………
Redsn0w for iOS 5 has received a minor update to make it compatible with iOS 5 Beta 4. The iPhone Dev Team, which authored this tweak, points out that this build, much like iOS 5 itself, is in beta form and should only be used by developers to test apps in the new iOS. It should also be noted that if you jailbreak your device on iOS 5, you wont get OTA updates from Apple, as explained by MuscleNerd of iPhone Dev-Team:
The 5.0b4 OTA update won’t work on JB devices due to an explicit check of /Applications..almost like a present from Apple
NOTE: It appears that by design, the OTA update that became available starting with iOS 5 beta4 will *not* be automatically applied to jailbroken devices. That’s a relief to those who don’t want to lose their jailbreak via OTA pushes. If you’re jailbroken, you’ll need to use the standard iTunes method to get to iOS 5 beta4.
Redsn0w is fairly easy to install and use, since the program itself provides concise instructions on all the manual steps that need to be followed. While that may be true, it’s recommended that you have basic knowledge on basic iOS maintenance tasks, including restoring and entering DFU mode, in order to proceed. Also, remember that jailbreaking your device will void your warranty. This is a tethered jailbreak, which means that the device will have to be plugged into the computer whenever it’s powered on, in order to be booted into a jailbroken state. It wouldn’t be worth for developers to work on an untethered method at this point, definitely not anytime before the final version of iOS finally ships. You will find the steps over here !!