[Verizon Samsung Galaxy S III] adiv.paradise:
So, I was trying to get Google Wallet to work on my VZW rooted Galaxy S3. I edited three lines in my build.prop. Specifically, my edits were

ro.product.model=Galaxy Nexus
ro.product.name=yakju
ro.product.device=maguro

They had been suggested on another site as a way to allow the installation of Google Wallet. In hindsight, probably shouldn't have gone with that advice. I did not perform a nandroid backup via CWM before starting, but did back up build.prop on my computer.

I rebooted my phone, and the phone got past the first Samsung logo, and then the Samsung Galaxy S3 screen, and went to a black screen after that. None of the buttons do anything, and the LED does nothing. Removing the battery is the only way to get back to a powered-off state from which I can re-enter the boot cycle. I can enter both recovery mode and download mode, and if I plug my phone into my computer at the black-screen point after normal boot, I can access the phone via adb.

So here's the real problem. I need to replace my build.prop with the backed-up version. In order to modify build.prop in the first place, I found that adb remount failed (I think I got permission denied or something), so after pulling build.prop, editing it, and saving it locally on the computer (using Ubuntu 10.04 LTS), I pushed the file to /mnt/sdcard/ so as not to encounter permission problems. I found that entering adb shell and going to su did not allow me to switch out the edited file, as I got a cross-device error. So in the phone I entered ES File Explorer (in which I enabled root explorer, and which I had previously used to remount the file system as read-write), and switched out the build.prop with my edited version.

Obviously, I cannot use my ES File Explorer trick to replace build.prop now that the phone is not working. So I try using adb shell. I again encounter the remount issue:

adiv@Onyx:/Onyx/adiv/android-sdk-linux_x86/platform-tools$ ./adb remount
remount failed: Operation not permitted

I saw elsewhere that the same can be accomplished via adb shell with su. So I try, and get this far:

shell@android:/ $ su
Segmentation fault

Definitely not good. Having now realized the error of my ways in not creating a nandroid before messing things up, I think, hey, I can make a nandroid now, pull the backup to my computer, and replace the build.prop in the backup, figure out how to update the MD5 sum, and recover from the modified backup. So I backup in CWM (recall that I can still enter recovery mode), pull the recovery, and take a look.

First I notice that the folder under clockworkmod/backup/ is quite oddly named 1970-01-30.22.07.14. I don't expect this to be a huge issue. I need to edit the system component, which I see seems to be distributed between system.ext4.tar.a (1.0 gb), system.ext4.tar (0 bytes), and system.ext4.tar.b (136.1 mb). I'm unable to unpack any of these three, as they don't seem to be packed like normal tarballs. And this is where I hit a dead-end for this method.

A third option which I admit I haven't fully explored is throwing the original build.prop in an update.zip and flashing that via recovery, and I haven't explored that option fully because I really have no idea what the inside of an update.zip looks like, or how I would go about building my own, and the few guides I looked at for building my own update.zip focused on either installing custom roms or installing apps, not replacing individual system files.

Any advice on where to go from here? I'd really rather not have to do a factory restore and re-apply root and re-install my apps and reconfigure everything and all that jazz, but if that's the only option I have, it's not like it's the end of the world--I can at least pull my data off the device using adb.

To summarize:

What I need to accomplish:

Replace my modified build.prop with the original build.prop that I backed up

Obstacles:

su in adb shell no longer appears to be working due to a "segmentation fault".

adb remount does not work, as the "Operation [is] not permitted."

I can't seem to unpack the system component of the nandroid backup, which has the wrong date.

How I thought I might fix it:

Use adb to push the new build.prop file and get it in its correct spot.

Edit a backup created by clockwork mod to have the correct build.prop and flash the backup via recovery.

Throw the correct build.prop in an update.zip file and install via recovery.

Any suggestions, ideas, or tips?

If I have to use option 3, does anybody have any tips as to building the update.zip? (Don't worry, if that's what I have to do, I'll do my due diligence and read up on update.zips and look through a few example update.zips)

Thanks,

Adiv