http://e2fsprogs.sourceforge.net/
http://www.linux.or.jp/JM/html/e2fsprogs/man8/debugfs.8.html
http://www.linux.or.jp/JF/JFdocs/Ext2fs-Undeletion/sec-modify.html
http://home2.highway.ne.jp/mutoh/bibo/b200003.html