How to fix Android ADB push error: Directory not empty

I am trying to put a .so file in /system/lib folder of 开发者_如何学JAVAemulator by using $ adb push /home/username/Development/newdroid/filename.so /system/lib

but it gives me error: failed to copy '/home/sudhir/Development/newdroid/libnfc_ndef.so' to '/system/lib/libnfc_ndef.so': Directory not empty

How do I fix this error?

try this command

mount -o rw,remount /dev/block/mtdblock3 /system