How To Convert An ext3/ext4 Root File System To btrfs On Ubuntu 12.10
ext3 and ext4 file systems can be converted to btrfs. For non-root
file systems, this can be done online (i.e., without reboot), while for
root file systems we need to boot into some kind of rescue system or
Live CD. This guide explains how to convert an ext3 or ext4 root file
system into btrfs on Ubuntu 12.10 and how to roll back to ext3/ext4
again if desired.