cubieboard3 如何扩展系统空间？

Question

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