我编译ANDROID4.1系统， 它编译完后有命令 make_ext4fs -s -l 268435456 -a system 产生system.img 系统文件，我用命令dumpe2fs out/target/product/beagleboard/system.img这个文件，显示找不到有效的文件系统超级块.这个文件我烧录到EMMC的一个分区，mount时就提示没有发现超级块。请问有知道的解释一下，怎么操作才好。
CMD='make_ext4fs -s -l 268435456 -a system out/target/product/beagleboard/obj/PACKAGING/systemimage_intermediates/system.img out/target/product/beagleboard/system'
+ echo make_ext4fs -s -l 268435456 -a system out/target/product/beagleboard/obj/PACKAGING/systemimage_intermediates/system.img out/target/product/beagleboard/system
make_ext4fs -s -l 268435456 -a system out/target/product/beagleboard/obj/PACKAGING/systemimage_intermediates/system.img out/target/product/beagleboard/system
+ make_ext4fs -s -l 268435456 -a system out/target/product/beagleboard/obj/PACKAGING/systemimage_intermediates/system.img out/target/product/beagleboard/system
Creating filesystem with parameters:
Size: 268435456
Block size: 4096
Blocks per group: 32768
Inodes per group: 8192
Inode size: 256
Journal blocks: 1024
Label:
Blocks: 65536
Block groups: 2
Reserved block group size: 15
Created filesystem with 1046/16384 inodes and 44826/65536 blocks
+ '[' 0 -ne 0 ']'
Running: mkuserimg.sh -s out/target/product/beagleboard/system out/target/product/beagleboard/obj/PACKAGING/systemimage_intermediates/system.img ext4 system 268435456
Install system fs image: out/target/product/beagleboard/system.img
out/target/product/beagleboard/system.img+ maxsize=274053120 blocksize=4224 total=181460636 reserve=2770944
make -C kernel ARCH=arm CROSS_COMPILE=arm-eabi- uImage
make[1]: 正在进入目录 `/work/mt3730/android4.1/jorjin_bsp/kernel'
make[1]:正在离开目录 `/work/mt3730/android4.1/jorjin_bsp/hardware/ti/wlan/mac80211/compat_wl12xx'
root@wqx-desktop:/work/mt3730/android4.1/jorjin_bsp# dumpe2fs out/target/product/beagleboard/system.img
dumpe2fs 1.41.11 (14-Mar-2010)
dumpe2fs: Bad magic number in super-block 当尝试打开 out/target/product/beagleboard/system.img 时
找不到有效的文件系统超级块.