I added as root user
/etc/rc.d/rc.local
/root/mount-vboxsf.sh
then
chmod +x /etc/rc.d/rc.local
and the sample script /root/mount-vboxsf.sh
(set your own the uid and gid options)
modprobe -a vboxguest vboxsf vboxvideo
mount -t vboxsf NAME_SHARED_DIRECTORY /media/sf_NAME_SHARED_DIRECTORY -o rw,uid=0,gid=0
you need add
chmod + /root/mount-vboxsf.sh