I tried to follow the rosbag tutorial (http://wiki.ros.org/ROS/Tutorials/Recording%20and%20playing%20back%20data), but when i arrive at the rosbag record -a command, the bag file isn't created. The only problem I may see is that the tutorial doesn't tell you where to exactly create the "bagfiles" directory.Apart from that, I don't know what else to do to make it work.