Modify /system/etc/vold.fstab
dev_mount sdcard /mnt/sdcard 3 /devices/platform/mmci-omap-hs.0/mmc_host/mmc0
The red word was changed into ‘auto’.
But I do not why I must do this. Another problem is still existed.
That is that “ls /sdcard” can not see any files. But “ls /mnt/sdcard” can see the files in the sdcard.
P.S. sdcard and /mnt/sdcard have a link.