刷了debian到cubieboard3的nand中， 现在还有一张8G的SD卡。 准备扩展/usr的空间大小
网站查了很久，查到两种方法：
1. 动态调整大小 （没弄懂）
2. 格式化SD卡 ，把/usr上的文件移动到SD上 ，然后挂载SD卡到/usr。
有点晕了求指导！
状态：
root@pc1:~# df -lh
Filesystem Size Used Avail Use% Mounted on
rootfs 4.0G 1.8G 2.1G 46% /
/dev/root 4.0G 1.8G 2.1G 46% /
devtmpfs 913M 0 913M 0% /dev
tmpfs 183M 508K 183M 1% /run
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 366M 0 366M 0% /run/shm
tmpfs 913M 4.0K 913M 1% /tmp
tmpfs 913M 0 913M 0% /var/tmp
root@pc1:~# fdisk -l
Disk /dev/nand: 7700 MB, 7700742144 bytes
255 heads, 63 sectors/track, 936 cylinders, total 15040512 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/nand doesn't contain a valid partition table
Disk /dev/nanda: 67 MB, 67108864 bytes
255 heads, 63 sectors/track, 8 cylinders, total 131072 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
Disk /dev/nandb: 4294 MB, 4294967296 bytes
255 heads, 63 sectors/track, 522 cylinders, total 8388608 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/nandb doesn't contain a valid partition table
Disk /dev/nandc: 3321 MB, 3321888768 bytes
255 heads, 63 sectors/track, 403 cylinders, total 6488064 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xffffffff
Disk /dev/nandc doesn't contain a valid partition table
Disk /dev/mmcblk0: 8054 MB, 8054112256 bytes
49 heads, 29 sectors/track, 11070 cylinders, total 15730688 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
/dev/mmcblk0p1 8192 15730687 7861248 b W95 FAT32