initrd-2.6.9-5.EL.img
解压
gzip -dc initrd-2.6.9-5.EL.img |cpio -div
压缩
find xxx yyy | cpio -ov -H crc |gzip -9> zz.cgz
解压缩 .cgz文件
cpio -divm <**.cgz

打开initrd.img文件
mv initrd.img initrd.gz
gzip -d initrd.gz
mount -o loop initrd /dir

gzip
 
   -d  decompress
   -c  write on standard output, keep original files unchanged
   -9  compress better

cpio

   -d  Create leading directories where needed
   -i   Extract files from an archive (run in copy-in mode)
   -v  Verbosely list the files processed
   -m  Retain previous file modification times when creating files
   -o   Create the archive (run in copy-out mode)
   -H  --format=FORMAT        Use given archive FORMAT