[Samsung Galaxy Gio GT-S5660] TripleRipple:
I have been researching the forums for a few weeks now but I have not stumbled across enough threads that would assist me to fully understanding the proper process for restoring via CWM back to a stock ROM (without going back to ODIN to flash it).

Of course this all relates to my Samsung Gio GT-S5660M from Bell in Canada (Pay as you Go). I really only purchased the phone to play with it to learn more. My wife has had the same phone for over a year. Her phone was rooted in order to be none carrier specific so she could use it to replace a phone under contract that was stolen. Other than that, it is stock.

I tried not to post and continue reading but now I am at the point where I need to ask a some specific questions.

First, some background as to what I am trying to do and what I have done so far.

The goal, as I am sure is the case with others, is to test custom ROMs but also be able to restore back to a factory default Samsung based ROM CWM backup at any point in the most convenient fashion.

I would like to perform this process with known working tools on this forum.

To start, I am familiar with the installation of the CWM from phiexz's work http://xdaforums.com/showthread.php?t=1421650. I have installed 5.0.2.7 via Flash from Recovery signed_cwm-5.0.2.7-flashablezip-ext4+rfs. After the installation of CWM I performed a backup of the stock rom.

Once that was complete, I began playing with some custom ROMs installing them via CWM off the SD card from zip files.

I learned after installing the custom ROMs that my phone was reformatted to EXT4 file system. This obviously makes it difficult to simply restore back to the stock ROMs original RFS file system easily. I received the obvious errors message (E:format_volume: format_rfs_device failed on /dev/block/stl12 Error while formatting /system!) when trying to restore the original ROM files via nandroid restore within CWM.

I have reviewed the nandroid backups stored on the SD card in the \clockworkmod\backup\appropriate dated file and I can see that the file names include RFS before the .tar extension for the system, data and cache files. From everything I have read this is normal since stock Samsung ROMs (at least FROYO and Gingerbread based ones) are based on the RFS file system as opposed to most custom ROMs which are based on EXT4. I made backups of some of the ROMs I was playing with from within CWM nandroid backup. I did notice those files had ext4 before the .tar extension in the file names. So I believe I am clear in understanding that portion.

I read that the only way to really get back to the RFS file version is to use ODIN to flash back the stock firmware all in one package retrieved from www.sammobile.com for the GT-S5660M for Bell in Canada. That again worked perfectly fine. I again went back into restore mode and re-installed signed_cwm-5.0.2.7-flashablezip-ext4+rfs. Once CWM was installed I tried to restore the original stock ROM backup I had saved originally and it gave me the same error (E:format_volume: format_rfs_device failed on /dev/block/stl12 Error while formatting /system!) even though I know the phone is now back at RFS file system again. Even when I try to perform a backup from CWM of the ODIN installed stock rom it complains stating (Backing up system.... Can't mount /system!.

I of course can reinstall Custom ROMs and restore them just fine after one initial installation and the file system being formatted back to EXT4.

So here are the questions.

1. What is the proper way to restore a stock ROM backup?

2. Is it possible to convert the RFS backup or existing system to EXT4 and have it still operate?

From what I can tell there is custom kernels that support EXT4 that can be injected via ODIN or CWM. Such as CF-ROOT however it is completely confusing to me on how to do that. I tried the ODIN method and that complained. I am not sure what version of CF-ROOT to use. Really I would like to stay with the EXT4 file system and convert the Stock backup to run with a custom ROM if need be. The goal is really just to be able to do it all within CWM and not require a computer other than for transferring files to the SD card as required.

I do not mind using ODIN but I would like to be able to restore with all the settings and changes I made in the stock OS to carry forward so I do not have to do that again.

3. Is there an easier or more reliable method to carry these steps out? Overall I would choose a method that consistently works over convenience.

Any assistance that could be provided would be appreciated.

Thank you in advance for your time in reading and/or hopefully replying to this thread.