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Note! Since the original position of the this guide, Android 2.2 has been formally released from Google. It is recommended that you just allow your device to update itself. Check for updates by going to Settings -> About Phone -> System Updates.

To root your N1 and get the latest and greatest rom, go to the Cyanogenmod site!

This guide explains how to install the latest version of the android OS (2.2 Froyo) on Rogers/AT&T version of the nexus one. There have been a ton of guides on how this works with the T-Mobile version, but very few for this one. Following the advice of this guide is to be done at your own risk, and we take no responsibility for any damage that may occur as a result.

First of all, you need to get your device to this firmware: ERE27, in order to do this you first have to flash your device to ERD79 and then update to ERE27. Once you have updated to ERE27, you can install the official 2.2 update. Here are the steps all broken down:

You should just follow the instructions on the on http://wiki.cyanogenmod.com/index.php?title=Nexus_One

1. Download the ERD79 stock ROM (boot, system and recovery partitions section)
2. Download ERE27 from the same site
3. Download the Fastboot flashing utility
4. Download the Android 2.2 update file – there are 2 links to the file in the first post on this site (first link is broken)
5. Flash the ERD79 using fastboot with the following command format: fastboot flash system system.img (google fastbook tutorial to find out a little more about how this tool works)
6. Update to ERE27 (using standard update method – see below)
7. Update to android 2.2 (using the standard update method – see below)

Standard Update Method

1. Rename the update file to update.zip
2. Note that if you’re using Windows and don’t have “show file extensions” turned on in the file explorer you won’t see a .zip. Just rename it to “update” (no quotes, of course) because it’s already a zipped file.
3. Copy the update.zip file onto the root of your microSD card (that means not in any folders)
4. With your Nexus One off, hold down the trackball and press the power button.
5. You’ll be booted into a white screen with three Android robots on skateboards. Select “Bootloader.”
6. On the next screen, select “Recovery.”
7. Your phone will reboot, giving you a picture of the Android robot and an exclamation point inside a triangle.
8. Now press the power button and volume up button at the same time. It could take a couple of tries.
9. Now (using the trackball this time) choose “Apply sdcard:update.zip” and let things run their course.