Filesystem messed up because of Apple's Mac OS X Disk Utility

[djpredator17]

I'm a happy Ubuntu user (Elementary OS 0.2 Luna).
I installed Luna on my Macbook 5,1 (late 2008). Everything works perfectly, even better than Mac OS X, but here is my problem:
- I used Utility Disk on the Mac partition, and it converted the Ubuntu's partition from ext4 to FAT32.
- The data are still there, but when I try to boot from Ubuntu it returns an 'unknown filesystem' error.
- I managed to boot from the grub rescue command line, and everything is working correctly.
- I booted from an USB stick
- How can I convert the filesystem back to EXT4 without losing data?
I can backup the whole thing and recreate the partition, but I'd prefer not to do it if possible.

Thank you!
Carlo

Here is my fdisk -l
Device Boot Start End Blocks Id System/dev/sda1 1 409639 204819+ ee GPT
/dev/sda2 * 409640 283217471 141403916 af HFS / HFS+
/dev/sda3 311954080 313223615 634768 af HFS / HFS+
/dev/sda4 313227264 492304383 89538560 c W95 FAT32 (LBA)

[lukeiamyourfather]

There's no such thing as converting from ext4 to FAT32 and vice versa. They are vastly different in design and implementation. The Disk Utility in OS X probably just changed some metadata and not the actual filesystem. If you can see your data in OS X at this point I'd take the opportunity to backup anything you haven't already.

[tgalati4]

You need to perform data rescue at this point--grab the important data and save it to a safe location. Changing file systems will normally resulting in wiping the partition and losing your data.

Install testdisk and run it and photorec (which comes with it).

[oldfred]

Not sure if it applies to a Mac or not, but you can change the partition table entry to a different code and partition table will show one type of format when partition is actually another type.
Also Macs sometimes use hybrid partitioning. That is required for Windows as Windows only booted with MBR, but drive is really gpt partitioned. But then you have to keep them sync'd.
http://www.rodsbooks.com/gdisk/hybrid.html


If you do not have gdisk on your live installer
sudo apt-get install gdisk
sudo gdisk -l /dev/sda
sudo fdisk -lu

[djpredator17]

Thanks to everybody for the quick replies, I'm gonna try some of your suggestions before wiping the disk if necessary.

[tgalati4]

Testdisk will fix the partition if it is fixable. Don't know how deep the Mac Disk Utility goes as far as formating. With luck, testdisk will get you back.