Setting the shared folder for VirtualBox between Ubuntu guest and Mac host is a very common need, but it spent me much to make it work! The following is the method I learned.
Guest Additions installation
The (by ozz314) gave me the first class:
You’ll need the latest version of VirtualBox (1.6) with Guest Additions installed in Ubuntu.
With the Virtual Machine powered off and selected in VirtualBox, go to:
Machine > Settings… > Shared Folders
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