Steps to remember, in case .vdi corrupts (again). Such a painful process!
Before installing GuestAdditions you should run these, otherwise shared folder and clipboard may not work.
sudo apt update && upgrade -y
reboot
sudo usermod -a -G vboxsf henryThese are for installing packages behind corporate proxy.
export http_proxy=http://192.168.10.15:8080
sudo echo 'Acquire::http::Proxy "http://192.168.10.15:8080"' >> /etc/apt/apt.conf
sudo apt install zlib1g-dev ruby-dev git gcc ake
sudo gem install bundler --http-proxy http://192.168.10.15:8080
bundle install