I try recover the backup superblock on /dev/sda2 that contain ubuntu 12.04 LTS and partition ext4 with livecd ubuntu 10.04. the message is below root@ubuntu:/home/ubuntu# fsck.ext4 -b 163840 -B 4096 /dev/sda2 e2fsck 1.41.11 (14-Mar-2010) /dev/sda2 was not cleanly unmounted, check forced. Resize inode not valid. Recreate? yes Pass 1: Checking inodes, blocks, and sizes Programming error? block #7963637 claimed for no reason in process_bad_block. Programming error? block #11240437 claimed for no reason in process_bad_block. Root inode is not a directory. Clear? yes Inode 712 is in extent format, but superblock is missing EXTENTS feature Fix? yes Inode 98519 has compression flag set on filesystem without compression support. Clear? yes Inode 98519 has INDEX_FL flag set but is not a directory. Clear HTree index? what's the correct procedure?