AN15 6-34页的原文：
Superblock corrupt?
Another thing you can try is to check the superblocks of your rootvg file systems. If you
boot in maintenance mode and you get error messages like Not an AIX file system
or Not a recognized file system type, it is probably due to a corrupt superblock in
the file system.
Each file system has two super blocks. Executing fsck should automatically recover
the primary superblock by copying from the backup superblock. The following is
provided in case you need to do this manually.
For JFS, the primary superblock is in logical block 1 and a copy is in logical block 31. To
manually copy the superblock from block 31 to block 1 for the root file system (in this
example), issue the following command:
# dd count=1 bs=4k skip=31 seek=1 if=/dev/hd4 of=/dev/hd4
For JFS2, the locations are different. To manually recover the primary superblock from
the backup superblock for the root file system (in this example), issue the following
command:
# dd count=1 bs=4k skip=15 seek=8 if=/dev/hd4 of=/dev/hd4
其中，man dd
seek=RecordNumber
Seeks the record specified by the RecordNumber variable from the beginning of output file before copying.
skip=SkipInputBlocks
Skips the specified SkipInputBlocks value of input blocks before starting to copy.
说明superblock是第二个block
参考linux的ext2文件系统（见鸟哥的linux私房菜）或者ext3 （http://www.linuxidc.com/Linux/2012-09/70710.htm），可能logical block是从0开始编号？block 0是boot block吗？
引导扇区（Boot Sector），又称之为引导块（Boot Block)是硬盘、软盘或其它数据存储设备上的一个包含引导代码的区域，这些代码可以由计算机系统的内置固件(firmware)加载到内存中直接运行。主要有两种类型：MBR和VBR
完整参考：http://en.wikipedia.org/wiki/Boot_sector