error: no sdcard inserted on pcduino

when you insert the micro sdcard to the pcduino, and try to

1, backup to sd card, 

2, Backup NAND to a SD card, and boot from SD card

there maybe an error "no sdcard inserted"

then try the following command 

$ sudo apt-get update
$ sudo apt-get install -y dosfstools
$ sudo apt-get install -y rsync

and then 

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/mmcblk0p2   15G  1.4G   13G  10% /

you could found the sdcard is mounted to /dev/mmcblk0p2

for more information, you could visit:

https://www.the-greathouses.net/blog/2013/03/pcduino-u-boot-part-2/comment-page-1/