I finally got my gentoo vagrant box up and running. There was a bug in vagrant which I was able to find a workaround. I also had to make sure that the vboxsf module is loaded on boot. Otherwise, I got and error:
Failed to mount folders in Linux guest. This is usually because the "vboxsf" file system is not available. Please verify that the guest additions are properly installed in the guest and can work properly. The command attempted was: mount -t vboxsf -o uid=`id -u vagrant`,gid=`getent group vagrant | cut -d: -f3` vagrant /vagrant mount -t vboxsf -o uid=`id -u vagrant`,gid=`id -g vagrant` vagrant /vagrant The error output from the last command was: /sbin/mount.vboxsf: mounting failed with the error: No such device
To fix this add
to the file /etc/conf.d/modules.
I was able to package the box after following another fix but I won’t be able to release the package until the above problems are fixed in the original vm.