The following works on CentOs / Fedora / redhat etc…
Logon to your distro. The packages you need are the kernel-devel.i686, kernel.i686 (if not the latest), and gcc.i386 (complier)
yum -y install kernel.i686 gcc.i386
reboot as the kernel needs to load, then logon again install the kernel dev;
yum -y install kernel-devel.i686
Now you want to present the virtualbox additions to the cdrom drive on your distro. Click “install additions” on the virtualbox guest console.
then back on the box mount the cdrom to a directory (make one if you dont have one avail)
mkdir /mnt/cdrom
mount /dev/cdrom /mnt/cdrom
Now go to the newly mounted cdrom drive and find the installation;
cd /mnt/cdrom
Execute the installer, and if all goes well reboot. Services should auto start and sync your time etc.
./VBoxLinuxAdditions-x86.run
reboot
logon and check your time;
date
Done.