What exactly do the Vagrant commands do?

I agree with you that documentation at vagrantup is on the shorter side.

Some information can be gleaned from command help system.

1. For example: gem command.

   Just type the command without arguments: vagrant gem -h and it produces the information that you may need.

   vagrant gem is used to install Vagrant plugins via the RubyGems
   system. In fact, vagrant gem is just a frontend to the actual gem
   interface, with the difference being that Vagrant sets up a custom
   directory where gems are installed so that they are isolated from your
   system gems.

2. Vagrant ssh-config:

   Under the hood, when you execute vagrant ssh to ssh into VM. It is utilizing it’s well known ssh key. The information on this key is provided by vagrant ssh-config. This is useful in case you want to change the well know key to your own private key and prepare boxes to use that.

   Also some times, you may want to use ssh based automation with your VMs. In that case, knowing which key is being used is useful. You could do use normal ssh command – ssh -i keyfile ..

3. vagrant status <vmname>

   This command is a wrapper which provides the information on the status of vm. It could be running, saved and powered off.

4. vagrant reload

   If you make any changes to the configuration in vagrantfile which needs to take effect. You may want to reload the VM. It re-runs the provisioning defined in the vagrantfile unless you ask it not too.

   It does not destroy the VM you have created from a base box. That means all the changes you have made to your VM, like say created a folder in your user directory will be there after reload.

   It is like reboot where it powers off your VM and then applies certain configuration change which can be applied only when VM has been powered off. and then power it on. Example: like attaching another SATA Virtual Disk.

5. vagrant up

   This reads your configuration file – vagrantfile and then creates a VM from base box. Base Box is like a Template. You can create many VMs from it.

   Similarly, vagrant destroy destroys your VM. In this case all changes you made when inside it will be lost. But thats the cool idea that you can start from a base predefined state when you create a new VM.

I really like using it and have blogged about it.

In summary, it is a good wrapper over VirtualBox APIs and Commands. You can have a look at the VirtualBox commands to understand some of the capabilities better.