Warning: Only specially packaged flashable dual boot ROMs like the ones I packaged below will flash to dual boot partition. Other flashable zips will overwrite your default boot.
Seems there is a problem flashing the zips from CWM on SD. See this post for a workaround, or use CWM on eMMC.
Just a word on booting into recovery. With the dual boot u-boot.bin, I have changed the button combo to VOL UP + VOL DOWN for recovery. So if you want to go to recovery, remember this is the key combo you need to hit. Not Power + n.
1. Prepare dual boot - http://dl.dropbox.com/u/20480343/prep-dualboot-0.1.zip
Flash this zip file will setup the dual boot partitions. If your NC is already setup using my previous dual boot script, there is no need to flash this again.
Note 1 - This does a resize of your /media partition. You data on /media should be intact. If you want to be safe, backup your /media before flashing.
Note 2 - /media partition will be resized to about 3.9 GB. If your existing data on /media is more that 3.9GB, you won't be able to flash this.
2. Remove dual boot - http://dl.dropbox.com/u/20480343/rem...alboot-0.1.zip
If you want to revert to stock, simply flash this file.
3. Dual boot ROMs
Now the dual boot ROMs. These will be flashed to the dual boot partitions (partition 9 and 10) on eMMC. Hold 'n' button while powering up to boot into dual boot ROM.
My modified u-boot.bin based on B&N 1.2 source - Seems previous version is having compatibility issues with 2.6.32 kernel. This is updated base on B&N 1.2 source. Flash using CWM. It only overwrites the u-boot.bin on boot partition. Boot message should show "(multi)U-Boot v0.3 loading..." after flashing this zip.
Flashable dual boot Nookie Froyo v0.6.8
Flashable dual boot Honeycomb Preview v04
Flashable dual boot HC v04 with gapps - credit goes to pauljohnson75
Flashable dalingrin's 1.1GHz OC kernel for dual boot HC - credit goes to dalingrin for the oc kernel, and pauljohnson75 for creating the dual boot flashable
Flashable zip to move your stock Eclair to dual boot partition v02 - This is not really a ROM strictly speaking. To avoid infringing B&N IP, no file from stock ROM is included in this zip. Scripts in this zip simply copies your stock ROM partitions and make the necessary adjustment to ramdisk. After flashing this, you will have an identical ROM setup on your dual boot partition. You are free to do whatever to your default ROM. For example, you can flash other ROMs to overwrite your default ROM. You will still be able to boot into stock eclair by holding 'n' button. Only thing to note is if the other ROMs you flash overwrites u-boot.bin, you will lose the dual boot capability.
Flashable dual boot CM7 nightly (cm_encore_full-22)
Note 1 - You can flash this using CWM 220.127.116.11. Newer version of CWM not required.
Note 2 - This will convert secondary /system and /data partitions to ext4. They will not be compatible with other dual boot ROMs any more. You need to flash remove-dualboot-0.1.zip, then prep-dualboot-0.1.zip, before flashing other dual boot ROMs.
Note 3 - This will wipe your dualboot data partition.
Link not longer working
cicada for Nookie Froyo. My update scripts are also based on his NF flashable.
deeper-blue for Honeycomb.
cm7 dev team for porting CM7 to NC
other xda developers who have contributed to NC community.