Well Google/T-Mobile is sending out a brand new RC30 update and you will be screwed out of root access if you install it, here is step by step directions to keep your r00t access to your G1:
First…. You need to install a google android usb driver so you can use the adb program. (It lets you push and pull files to/from the phone, and you can open up a shell with it to).
(you dont need to do this if your in linux)
Download the driver file (http://dl.google.com/android/android_usb_windows.zip) and
unzip it to the desktop.
On ur G1… Go menu > Settings > Applications > Development then enable the
USB debugging button.
Then connect your Android device via USB. When the Found New Hardware Wizard
appears, you'll be asked if you'd like Windows Update to search for software,
select No, not this time and click Next. Select Install from a list or specified location
and click Next. Select Search for the best driver in these locations. Browse and
select the unzipped file (android usb windows.zip). Click Finish.
Second…. Setting up the SDK
Go to http://code.google.com/android/download_list.html and download the
Make a folder called SDK on the desktop
Unzip the files to the folder SDK
Open your command prompt (Windows Key and R)
Type “cmd” (Without the quotations)
Then “cd sdk”
Next “cd tools”
Now type “adb devices
After that it should say some thing like… List of devices attached HT845GZ21370
Device. If u see this abd sees your device.
Third…. Writing JesusFreke’s Recovery image
Download the zip file from this thread... http://forum.xda-developers.com/showthread.php?t=443041)
Unzip the files to the SDK tools folder
Now, in the command window, type
"adb push recovery_testkeys.img /data/local/recovery.img"
(This will copy the recovery image files to the phone)
Fourth…. Get Root working on ur G1
Download the Android Telnet Client from the Market or get it here…
Turn on your phone's WiFi. This gives your phone an IP you can reach it at.
Restart your phone
Once restarted type telnetd at the home screen and press enter – Yes….. it will
start up a Contact search, do not worry about this, just type “telnetd” and press
enter (the enter button on the keypad).
Now press connect to localhost……. (You now have root!)
Now put in this command….
“mount -o rw,remount -t yaffs2 /dev/block/mtdblock3 /system”
Then “cd /system”
Then “cat /data/local/recovery.img > recovery.img”
Finally “flash_image recovery recovery.img” (Your Recovery Image is no writen)
*To make sure your Recovery Image was written…. Reboot your phone in Recovery
mode and press Alt+L. At the top it should say "using test keys" If so its written. Go
ahead and Reboot your phone by pressing the Home and Back buttons.*
Fifth…Apply JesusFreke’s modified RC30
Go here http://rapidshare.com/files/162035634/update-RC30-fullupdate-modified-testkeys-v1.1.zip and Download the ZIP
Now once the ZIP is downloaded rename it to “UPDATE”
Put it on the storage card
Last but not least Reboot you phone in recovery
Press Alt+L (to turn on text)
Press Alt+S (to update)
And Bam you have yourself a modded RC30 G1 !!!!!!!!
Complements to usmc2k for writing this howto