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Droid X on RootzWiki
If you already have root, and want to install the 2.2 leak but keep root
FROM A ROOTED PHONE (using ADB):
1. Run "adb shell"
2. Run "mount -o rw,remount /dev/block/system /system"
3. Run "mv /system/bin/su /system/xbin/su"
4. Copy the update.zip (download below) to your sdcard
5. Reboot into recovery (power down - hold volume down and home button and press the power button)
6. Run the update.zip that you downloaded
You can also do it using Root Explorer if you want.