查看镜像分区情况：
[email protected]:/mnt/down $ fdisk -l 2018-03-13-raspbian-stretch-lite.img
2018-03-13-raspbian-stretch-lite.img1 8192 93802 85611 41.8M c W95 FAT32 (LBA)
2018-03-13-raspbian-stretch-lite.img2 98304 3629055 3530752 1.7G 83 Linux
利用 dd 命令 skip 跳过指定块写入到目标分区：
sudo dd if=2018-03-13-raspbian-stretch-lite.img of=/dev/sda2 bs=1M skip=48