[Nook Color Android Development] fattire:
SD Card Backupper App Idea 4 Nooks

This is exciting stuff, and a long time coming IMO. As we discussed, there's also the fun idea of writing an SD<->EMMC cross-installer app for all the nooks, which in its simplest form would take a live, running emmc install and make a blank, freshly-formatted, bootable SD card, formatting the right partitions, then copying /boot and /system from the emmc to the SD.

A more detailed view of "SDCard Maker.apk" or whatever-- it does this, basically:

detects if it's running on Nook Color, Tablet, HD, or HD+. Bails if it's not one of these.

Based on the above, loads the appropriate partition scheme.

Verifies /system is mounted to mmc0 (or otherwise makes sure it's running off of internal emmc). If not, it reverses the steps that follow.

Requests the user insert a blank SD card (if the OS is not running off SD, that is)

Warns the user that the SD is about to be wiped and reformatted (or alternately, that emmc is about to have its OS reinstalled)

Requests Superuser Permission & bails if it doesn't get it.

If running from internal emmc, wipes SDCard and sets up partitions (appropriate for SD size). If running from SD, reformats/resizes internal EMMC.

Copies /boot files from emmc->SD (or vice versa) including bootloader, basic kernel/ramdisk & recovery as needed. Alternately goes the other way-- for Nook Tablet, HD, and HD+ it must be mindful of 2nd bootloader/Cyanoboot stuff to make sure everything is as it should be. Until the "One Image To Rule Them All" version Steven676 is suggesting, a simple script could modify the init.encore.rc file as needed.

Similarly backs up contents of /system. If the user already has Gapps on their machine, then making a SD backup should fall within fair use so long as the SDcard is not distributed. Or make a back up of a raw cyanogenmod .zip install w/o gapps... (Similarly, a booted OS from SD card could be transferred fully to emmc...)

Not ridiculously hard I'd think, especially for someone who's written Android apps (or wants to learn)... should be GPL'd...

It's not that big a challenge to get derp running on Windows. Check out the end of the thread. It's running already, though some fine tuning is needed from someone who actually HAS windows. (And there's a licensing issue for some .DLLs where someone with Virtual Studio something something needs to distribute it.) The biggest challenge as I see it on any platform though would be 100% identifying exactly where the sdcard has been inserted-- via a SD slot, usb adapter, etc. You really don't want to accidentally dd over the user's hard drive, after all. (Of course, this is an issue any time you're suggesting a user flash to a SD card, derp or no derp).

Ideally, you'd run derp on your platform (a .deb for Linux, Derp.app for OS X, or Derp.exe for Windows), it updates adb and fastboot to the latest version, then it would auto-download a nightly .img, instruct you to pop the SD card into your computer, and with a click it's flashed.

97% of this is already written. It just needs a very simple xml "derp" script to find the .img (the download code is there already), and maybe download the dd equivalent of windows... then just do it. Probably want to code some sanity checks to make sure the target device is correct, and add some text/pictures to help a beginner understand what they're doing...

After all the work that went into derp (way before a certain OTHER windows-only installer I might add- and this one's GPLv3... cough), it would be nice to see it get some use/testing/improvements :) Docs are in the link above.