如何通过Vagrant/VirtualBox安装Ruby和Rails？版本不符求助

尝试手动安装Ruby一周未果，改用Vagrant搭配VirtualBox的ubuntu/trusty64镜像，通过bootstrap.sh和Vagrantfile实现自动化安装。但明明配置了指定版本，却始终无法安装正确的Ruby和Rails版本。执行vagrant up、vagrant ssh后，在终端输入ruby -v和rails -v，结果与预期不符（附截图）。

以下是我的bootstrap.sh和Vagrantfile文件：

bootstrap.sh #

#!/usr/bin/env bash
# 升级系统
echo upgrading and updating the system
sudo apt-get update
sudo apt-get -y upgrade
# 安装node.js作为Rails的JS运行时及git
echo installing nodejs for ExecJS runtime and git
sudo apt-get install -y nodejs
sudo apt-get install -y git
# 安装RVM
echo installing RVM
gpg --keyserver hkp://keys.gnupg.net --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3 7D2BAF1CF37B13E2069D6956105BD0E739499BDB
\curl -sSL https://get.rvm.io | bash -s stable
source /home/vagrant/.rvm/scripts/rvm
rvm requirements
# 安装Ruby 2.3.1并设为默认版本
echo installing ruby
rvm install 2.3.1
rvm use 2.3.1 --default
# 安装Bundler和Rails 4.2.7
echo installing bundler and rails
gem install bundler --no-ri --no-rdoc
gem install rails -v 4.2.7 --no-ri --no-rdoc
# 安装PostgreSQL及依赖
echo installing psql and its dependencies
sudo apt-get install -y postgresql postgresql-contrib libpq-dev

Vagrantfile #

Vagrant.configure("2") do |config|
  config.vm.box = "ubuntu/trusty64"
  config.vm.network "forwarded_port", guest: 3000, host: 3000, host_ip: "127.0.0.1"
  config.vm.provision :shell, path: "bootstrap.sh", privileged: false
  config.vm.provider "virtualbox" do |vb|
    vb.customize ["modifyvm", :id, "--memory", "2048"]  
    vb.customize ["modifyvm", :id, "--cpus", "2"]  
  end
end

内容的提问来源于stack exchange，提问作者Keith Coye