Android: make the system partitions on the device read-write

From the SDK's tools directory, run adb shell. In the
prompt run the following:

# su
# mount -o rw,remount -t yaffs2 /dev/block/mtdblock4 /system
# chmod 777 /system (Or any subdirectory you want to push to inside system)
# exit
adb push

and eventually you should restore the original directory permissions by:
# chmod 755 /system (Or any subdirectory you modified permissions to)

Make sure you knew the mount point for system by running #
# cat /proc/mtd
dev: size erasesize name
mtd0: 00500000 00020000 "boot"
mtd1: 04000000 00020000 "cache"
mtd2: 00500000 00020000 "recovery"
mtd3: 00060000 00020000 "splash"
mtd4: 0f500000 00020000 "system"
mtd5: 002c0000 00020000 "lgdrm"
mtd6: 08b80000 00020000 "userdata"
mtd7: 00080000 00020000 "usd"
mtd8: 005a0000 00020000 "pkg"
mtd9: 1cfc0000 00020000 ""