How to create a symlink after I rooted my Samsung galaxy w GT-i8150? How do I create a symlink from my /sdcard/NaviSEA to point to /sdcard/external_sd/SD/NaviSEA?

Even after rooting my device I still get "Operation not permitted" error and I did allow with su in my script :

$ su
# ln -s /sdcard/external_sd/SD/NaviSEA /sdcard/NaviSEA


Why doesn't my script work?
Your external SD card is presumably (in pretty much every case) formatted as a FAT32 filesystem. FAT32 does not support symbolic links. Linking from a ext2/3/4 filesystem to a FAT32 filesystem would work, IIRC, but linking from FAT32 isn't possible.