Start Docker error message

I was trying to run “docker -d” command to start docker service and install dokku by myself, but I got an error message. Any idea? Thanks!

Environment: Ubuntu+Nginx+RoR+Unicorn

Error Message: <pre> [2758c589] +job serveapi(unix:///var/run/docker.sock) [2758c589] +job initserver() [2758c589.initserver()] Creating server [2758c589] +job init_networkdriver() 2014/06/14 02:19:41 Listening for HTTP on unix (/var/run/docker.sock) [2758c589] -job init_networkdriver() = OK (0) 2014/06/14 02:19:41 WARNING: Your kernel does not support cgroup swap limit. Error loading docker apparmor profile: exec: “/sbin/apparmor_parser”: stat /sbin/apparmor_parser: no such file or directory () [2758c589] -job initserver() = ERR (1) 2014/06/14 02:19:41 Error loading docker apparmor profile: exec: “/sbin/apparmor_parser”: stat /sbin/apparmor_parser: no such file or directory () </pre>