Root allows you to modify just about everything, flash new images, change your boot image, change themes, run ARM debian, and tons more. This guide goes through installing/downgrading to RC29, getting root, flashing the new recovery.img / test keys, changing the boot loader, and installing JesusFreke's modified RC33 builds. If you're using a Rogers G1, this process will not work for you. See this. If you're unsure about why you would want root, or aren't comfortable with flashing or poking around on your device, do not do this. Update (3/10/09): Switched from RC30 to RC33 instructions, and clarified a few points. Sources JesusFreke's modified updates Registering without a sim or data plan Modded recovery and boot images Dream SPLs RC30 to JFv1.31 And all of the great people over at xda-developers and freenode/#android who make it all happen. Let's get started. Also, please note that this will wipe out everything - all of your settings and apps - twice. By installing the RC29 nbh, you lose everything, and likewise moving to RC33. There's 4 main files you're going to need: DREAIMG.nbh This is the NBH file needed to roll back to RC29. recovery_testkeys.img The modified recovery image/test keys. EngBootloader_v2_NoSigCheck.zip The engineering bootloader. An update.zip. It's recommended that you read more about them here before choosing this one. JFv1.42_RC33 JesusFreke's (latest, at time of writing) modified RC33 update.zip. RC33 Radio update The radio update to apply when moving to RC33. Once you have all of the files, you're ready to go. Once again, if you're unsure about why you would want root, or aren't comfortable with flashing or poking around on your device, do not do this. It's definitely recommended that your phone's battery life remaining be full or near full when you start this, as it can take awhile depending on how quickly you do the steps. Step 1) - Format the Micro SD Card to FAT32. - Copy the DREAIMG.nbh file to the Micro SD Card. - With the phone off, hold camera and press power to boot into the bootloader. - Once the bootloader is loaded, press power to install. - Press the trackball to continue and press talk+menu+power to reboot. Step 2) - Copy recovery_testkeys.img onto the Micro SD Card. - Turn the phone on (if not already) - Type enter telnetd enter to start telnet - Telnet into the phone with telnet (telnet ipaddress) OR use the telnet application from the market and connect to localhost - Run the following as root (in telnet) Code (Text): mount -o rw,remount -t yaffs2 /dev/block/mtdblock3 /system dd if=/system/bin/sh of=/system/bin/su chmod 4755 /system/bin/su And you've created su, a way to switch to the root user easily. Now we need to add the modified recovery test keys. Run the following in telnet again (or as root). It's also a good idea to note that the sdcard must be unmounted at this point, so if you moved the recovery image to your phone using the phone, unmount it first. Code (Text): su cd /system cat /sdcard/recovery_testkeys.img > recovery.img flash_image recovery recovery.img Now that's finished. Personally, I prefer to go with the Engineering bootloader, but you can choose whichever you'd like. Step 3) - Rename whichever bootloader package you're going to use to update.zip - Copy it onto the Micro SD Card. - Turn off the phone (if not already,) - Hold home+power to boot into recovery mode - Alt+L to see the text - Alt+S to install the bootloader - When it's done, reboot And now you've got the bootloader. Last but not least, if you'd like, you can install JesusFreke's RC33 builds that add a lot of extra goodness. Step 4) Note: It's recommended elsewhere that you wipe your data (Alt+W in Recovery Mode) before applying this update. Although I don't do this myself, doing so never hurts. - Rename to update.zip - Copy it onto the Micro SD Card. - Turn off the phone (if not already,) - Hold home+power to boot into recovery mode - Alt+W to wipe the data, as noted above, if you so choose - Alt+L to see the text - Alt+S to install the update - When it's done, reboot Step 5) - Repeat the same process as in Step 4 with the RC33 Radio update. This update will restart your phone a few times and display the 'flashing rom' graphic, be patient, as it can take some time. And now you're done. Easy as pie.