Share files between Mac OS as host and CentOs as guest

Shared folder:
Host: Mac OS
Guest: centOs 5.6
1. Click Settings on VirtualBox, and then click Shared Folders.
2. Add Machine Folders (the shared folder on the host machine), setup a name as shared_folder and make it permanent.
3. In your Guest Linux Box, open a terminal and enter the following commands:
>sudo mkdir /mnt/share 
>sudo mount -t vboxsf shared_folder /mnt/share     [shared_folder is the name of your shared folder]
4. Make the mounted share permanent, you can make the shared folder mount automatically each time you start the CentOS guest, enter the following commands:
>sudo vim /etc/fstab
add a line at the bottom of the file, it looks like this:
shared_folder /mnt/share vboxsf rw,gid=100,uid=1000,auto 0 0
5. restart your guest system, and verfy your settings, it should work.