Ok, the next is best solution:
int date = (int) System.currentTimeMillis();
String source = "/system/etc/gps.conf";
String destination = "/system/etc/gps" + date + ".conf";
if(RootTools.remount("/system/etc/", "rw")){
RootTools.copyFile(source, destination, true, true);
}
The problem is that previously I pointed to /etc, but this location is a symlink, the real path is /system/etc. Obviously we can't change mount type of a symlink, so, the previous code that I just have posted, is the good answer.
Thanks.