Add docs for action hooks

Fixes GH-6271

website/docs/source/layouts/layout.erb

@@ -269,6 +269,7 @@
 								<ul class="sub unstyled">
 									<li<%= sidebar_current("plugins-usage") %>><a href="/v2/plugins/usage.html">Usage</a></li>
 									<li<%= sidebar_current("plugins-development-basics") %>><a href="/v2/plugins/development-basics.html">Plugin Development Basics</a></li>
+									<li<%= sidebar_current("plugins-action-hooks") %>><a href="/v2/plugins/action-hooks.html">Action Hooks</a></li>
 									<li<%= sidebar_current("plugins-commands") %>><a href="/v2/plugins/commands.html">Commands</a></li>
 									<li<%= sidebar_current("plugins-configuration") %>><a href="/v2/plugins/configuration.html">Configuration</a></li>
 									<li<%= sidebar_current("plugins-guests") %>><a href="/v2/plugins/guests.html">Guests</a></li>
@@ -277,7 +278,7 @@
 									<li<%= sidebar_current("plugins-hostcapabilities") %>><a href="/v2/plugins/host-capabilities.html">Host Capabilities</a></li>
 									<li<%= sidebar_current("plugins-providers") %>><a href="/v2/plugins/providers.html">Providers</a></li>
 									<li<%= sidebar_current("plugins-provisioners") %>><a href="/v2/plugins/provisioners.html">Provisioners</a></li>
-									<li<%= sidebar_current("plugins-packaging") %>><a href="/v2/plugins/packaging.html">Packaging & Distribution</a></li>
+									<li<%= sidebar_current("plugins-packaging") %>><a href="/v2/plugins/packaging.html">Packaging &amp; Distribution</a></li>
 								</ul>
 								<% end %>
 

website/docs/source/v2/plugins/action-hooks.html.md

@@ -0,0 +1,100 @@
+---
+page_title: "Plugin Development Basics - Action Hooks"
+sidebar_current: "plugins-action-hooks"
+---
+
+# Action Hooks
+
+Action hooks provide ways to interact with Vagrant at a very low level by
+injecting middleware in various phases of Vagrant's lifecycle. This is an
+advanced option, even for plugin development.
+
+<div class="alert alert-warn">
+  <p>
+    <strong>Warning: Advanced Topic!</strong> Developing plugins is an
+    advanced topic that only experienced Vagrant users who are reasonably
+    comfortable with Ruby should approach.
+  </p>
+</div>
+
+
+## Public Action Hooks
+
+The following action hooks are available in the core of Vagrant. Please note
+that this list is not exhaustive and additional hooks can be added via plugins.
+
+- `environment_plugins_loaded` - called after the plugins have been loaded,
+  but before the configurations, provisioners, providers, etc. are loaded.
+
+
+- `environment_load` - called after the environment and all configurations are
+  fully loaded.
+
+
+- `environment_unload` - called after the environment is done being used. The
+  environment should not be used in this hook.
+
+
+- `machine_action_boot` - called after the hypervisor has reported the machine
+  was booted.
+
+
+- `machine_action_config_validate` - called after all `Vagrantfile`s have been
+  loaded, merged, and validated.
+
+
+- `machine_action_destroy` - called after the hypervisor has reported the
+  virtual machine is down.
+
+
+- `machine_action_halt` - called after the hypervision has moved the machine
+  into a halted state (usually "stopped" but not "terminated").
+
+
+- `machine_action_package` - called after Vagrant has successfully packaged a
+  new box.
+
+
+- `machine_action_provision` - called after all provisioners have executed.
+
+
+- `machine_action_read_state` - called after Vagrant has loaded state from
+  disk and the hypervisor.
+
+
+- `machine_action_reload` - called after a virtual machine is reloaded (varies
+  by hypervisor).
+
+
+- `machine_action_resume` - called after a virtual machine is moved from the
+  halted to up state.
+
+
+- `machine_action_run_command` - called after a command is executed on the
+  machine.
+
+
+- `machine_action_ssh` - called after an SSH connection has been established.
+
+
+- `machine_action_ssh_run` - called after an SSH command is executed.
+
+
+- `machine_action_start` - called after the machine has been started.
+
+
+- `machine_action_suspend` - called after the machine has been suspended.
+
+
+- `machine_action_sync_folders` - called after synced folders have been set up.
+
+
+- `machine_action_up` - caled after the machine has entered the up state.
+
+
+## Private API
+
+You may find additional action hooks if you browse the Vagrant source code, but
+only the list of action hooks here are guaranteed to persist between Vagrant
+releases. Please do not rely on the internal API as it is subject to change
+without notice.