adding Vagrant Virtualbox to install mac page

Author: vsoch

pages/docs/install/install-mac.md

@@ -7,22 +7,46 @@ folder: docs
 
 This recipe demonstrates how to run Singularity on your Mac via Vagrant and Ubuntu. The recipe requires access to `brew` which is a package installation subsystem for OS X. This recipe may take anywhere from 5-20 minutes to complete.
 
+## Setup
+
+First, install brew if you do not have it already.
+
 ```bash
-# Install Brew if you do not have it installed already
 /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
+```
 
-# The next commands will install Vagrant and the necessary bits
+Next, install Vagrant and the necessary bits.
+
+```bash
 brew cask install virtualbox
 brew cask install vagrant
 brew cask install vagrant-manager
+```
 
-# Create a working directory for the Vagrant configuration and
-# generate a template Vagrantfile for "bento/ubuntu-16.04"
+## Option 1: Singularityware Vagrant Box
+
+We are maintaining a set of Vagrant Boxes via <a href="https://atlas.hashicorp.com/" target="_blank">Atlas</a>, one of <a href="https://www.hashicorp.com/#open-source-tools" target="_blank">Hashicorp</a> many tools that likely you've used and haven't known it. The <a href="https://atlas.hashicorp.com/singularityware/boxes/singularity-2.2.99" target="_blank">Singularity Box</a> is for version 2.2.99, and will be updated appropriately with the release of 2.3. To use this box, you can simply create a folder, and then do the following:
+
+```bash
+mkdir singularity-vm
+cd singularity-vm
+vagrant init singularityware/singularity-2.2.99
+vagrant ssh
+```
+
+## Option 2: Vagrant Box from Scratch
+
+If you want to use a different version of Singularity, or want to get more familiar with how Vagrant and VirtualBox work, you can build your own Vagrant Box from scratch.  In this case, we will use the Vagrantfile for `bento/ubuntu-16.04`, however you could also try any of the <a href="https://atlas.hashicorp.com/bento" target="_blank">other bento boxes</a> that are equally delicious. As before, you should first make a separate directory for your Vagrantfile, and then init a base image.
+
+```bash
 mkdir singularity-vm
 cd singularity-vm
 vagrant init bento/ubuntu-16.04
+```
 
-# Build and start the Vagrant hosted VM
+Next, build and start the vagrant hosted VM, and you will install Singularity by sending the entire install script as a command (with the `-c` argument). You could just as easily shell into the box first with vagrant ssh, and then run these commands on your own. To each bento, his own.
+
+```bash
 vagrant up --provider virtualbox
 
 # Run the necessary commands within the VM to install Singularity
@@ -36,11 +60,12 @@ vagrant ssh -c /bin/sh <<EOF
     make
     sudo make install
 EOF
+```
 
-# Singularity is installed in your Vagrant Ubuntu VM! Now you can
-# use Singularity as you would normally by logging into the VM
-# directly
+At this point, Singularity is installed in your Vagrant Ubuntu VM! Now you can use Singularity as you would normally by logging into the VM directly
+
+```bash
 vagrant ssh
 ```
 
-Remember that the VM is running in the background because we started it via the command `vagrant up`. You can shut the VM down using the command 'vagrant halt' when you no longer need it.
+Remember that the VM is running in the background because we started it via the command `vagrant up`. You can shut the VM down using the command `vagrant halt` when you no longer need it.