setup your VirtualBox guest to export a folder to you host Mac

nfs-setup.sh

if [[ $(uname -a) = *Darwin* ]]; then
    echo "Run this from your Linux guest, not your Mac";
else
sudo apt-get install nfs-kernel-server
sudo mkdir /export
sudo chmod a+rwx /export
mkdir /export/devel
sudo mount --bind $HOME/devel /export/devel
cat <<EOF | sudo tee -a /etc/fstab

# added per https://help.ubuntu.com/community/SettingUpNFSHowTo
$HOME/devel	/export/devel	none	bind	0	0
EOF

cat <<EOF | sudo tee -a /etc/default/nfs-kernel-server

# added per https://help.ubuntu.com/community/SettingUpNFSHowTo
NEED_SVCGSSD=no # no is default
EOF

cat <<EOF | sudo tee -a /etc/default/nfs-common

# added per https://help.ubuntu.com/community/SettingUpNFSHowTo
NEED_IDMAPD=yes
NEED_GSSD=no # no is default
EOF

cat <<EOF | sudo tee -a /etc/exports

# added per https://help.ubuntu.com/community/SettingUpNFSHowTo
/export       192.168.56.0/24(rw,fsid=0,insecure,no_subtree_check,async)
/export/devel 192.168.56.0/24(rw,nohide,insecure,no_subtree_check,async,anonuid=1000,anongid=1000,all_squash)
EOF

sudo /etc/init.d/nfs-kernel-server restart
cat << EOF
Now you can mount your devel folder on your Mac in either of the following ways:
    via Finder:
        Cmd-K and mount nfs://192.168.56.101/export/devel
    via CLI:
        sudo mount -t nfs -o hard,intr -o -P 192.168.56.101:/export/devel /Network
EOF
fi