[Vibrant General] vnamee:
I just wanted to share a story of woe and redemption so that it doesn't happen to you.

As background, I had sim unlocked my phone using helroz's method a while back, and my phone has been working fine from team whiskey's early days till now. Recently, I was flashing my phone as most of us do. I noted that after flashing the dead horse kernel, my market was not working properly, so I decided to odin back to JFD. From there, I flashed Bionix, but afterward, noted that I wasn't getting any cell reception. After some investigation and several odins, I looked at my software info and found that my baseband was unknown. I flashed back to JFD however, and it worked fine. In fact, this was the only rom where the cell worked. The phone otherwise was functioning flawlessly, including wifi.

Further investigation showed that this has happened to others, and anecdotally, people have fixed it by odining over and over or doing some magic with their sim card. I did just that but to no avail. After some thinking, it occurred to me that maybe my /efs data was bad, so I took a look. Hitting *#06# showed the generic samsung IMEI while in JFD (it did not work in other versions as the baseband was not working), not my normal IMEI. That's odd. I still had the backup from trying to sim unlock it months ago. I tried to overwrite the /efs folder w/ my own, but I could not write it due to 'not enough space.'

Further investigation showed that indeed, my efs partition had been borked, and so I could not write data to it (I could copy however). The only way to fix this is by flashing/odin'ing a new partition. This only works if you have a backup, which I didn't. Basically, I had a fancy media player at this point.

I went ahead and looked on craigslist and found a vibrant w/ a broken screen, figuring I could swap out the guts. I immediately backed up the /efs folder and partition of the broken phone, just in case. On a whim, I tried to flash the efs partition from the broken phone to my phone. Lo and behold, the baseband came back. I was now able to write to that partition, so overwrote the /efs folder w/ my backup from before. My IMEI came back afterwards, and so now, I have 2 functioning vibrants. I'm not sure what data is stored in /dev/block/stl3, but I do know I was able to fix my phone using another phone's data. They both work w/ my sim, though I am unsure if they can connect simultaneously using different sims or if they are somehow cloned, but the IMEIs are different for sure.

The moral of the story is that this phone is nigh unbrickable and even when it doesn't boot, you can always try the jig. The only part of the phone you can't fix w/ a routine odin it seems, is the efs partition, so I would encourage everyone to make a backup and keep it safe. This is not done standard as an initiation into rooting and roms and such, but it should be. Normally, odin'ing a rom does not write to this area, but even w/o screwing with this, frequent flashing and odins can apparently corrupt it, leaving you high and dry. With this backup and odin, you could probably fix your phone from any jam.

Here are the relevant threads on how to do this:

http://xdaforums.com/showthread.php?t=882039

http://xdaforums.com/showthread.php?t=859914

Keep those backups safe!