add new cli alias documentation

website/source/docs/cli/aliases.html.md

@@ -0,0 +1,74 @@
+---
+layout: "docs"
+page_title: "Aliases - Command-Line Interface"
+sidebar_current: "cli-aliases"
+description: |-
+  Custom Vagrant commands can be defined using aliases, allowing for a simpler,
+  easier, and more familiar command line interface.
+---
+
+# Aliases
+
+Inspired in part by Git's own
+[alias functionality](https://git-scm.com/book/en/v2/Git-Basics-Git-Aliases),
+aliases make your Vagrant experience simpler, easier, and more familiar by
+allowing you to create your own custom Vagrant commands.
+
+Aliases can be defined within `VAGRANT_HOME/aliases` file, or in a custom file
+defined using the `VAGRANT_ALIAS_FILE` environment variable, in the following
+format:
+
+```
+# basic command-level aliases
+start = up
+stop = halt
+
+# advanced command-line aliases
+eradicate = !vagrant destroy && rm -rf .vagrant
+```
+
+In a nutshell, aliases are defined using a standard `key = value` format, where
+the `key` is the new Vagrant command, and the `value` is the aliased command.
+Using this format, there are two types of aliases that can be defined: internal
+and external aliases.
+
+## Internal Aliases
+
+Internal command aliases call the CLI class directly, allowing you to alias
+one Vagrant command to another Vagrant command. This technique can be very
+useful for creating commands that you think _should_ exist. For example,
+if `vagrant stop` feels more intuitive than `vagrant halt`, the following alias
+definitions would make that change possible:
+
+```
+stop = halt
+```
+
+This makes the following commands equivalent:
+
+```
+vagrant stop
+vagrant halt
+```
+
+## External Aliases
+
+While internal aliases can be used to define more intuitive Vagrant commands,
+external command aliases are used to define Vagrant commands with brand new
+functionality. These aliases are prefixed with the `!` character, which
+indicates to the interpreter that the alias should be executed as a shell
+command. For example, let's say that you want to be able to view the processor
+and memory utilization of the active project's virtual machine. To do this, you
+could define a `vagrant metrics` command that returns the required information
+in an easy-to-read format, like so:
+
+```
+metrics = !ps aux | grep "[V]BoxHeadless" | grep $(cat .vagrant/machines/default/virtualbox/id) | awk '{ printf("CPU: %.02f%%, Memory: %.02f%%", $3, $4) }'
+```
+
+The above alias, from within the context of an active Vagrant project, would
+print the CPU and memory utilization directly to the console:
+
+```
+CPU: 4.20%, Memory: 11.00%
+```

website/source/docs/other/environmental-variables.html.md

@@ -14,6 +14,11 @@ Vagrant has a set of environmental variables that can be used to
 configure and control it in a global way. This page lists those environmental
 variables.
 
+## `VAGRANT_ALIAS_FILE`
+
+`VAGRANT_ALIAS_FILE` can be set to change the file where Vagrant aliases are
+defined. By default, this is set to `~/.vagrant.d/aliases`.
+
 ## `VAGRANT_DEBUG_LAUNCHER`
 
 For performance reasons, especially for Windows users, Vagrant uses a static

website/source/layouts/docs.erb

@@ -44,6 +44,7 @@
           <li<%= sidebar_current("cli-validate") %>><a href="/docs/cli/validate.html">validate</a></li>
           <li<%= sidebar_current("cli-version") %>><a href="/docs/cli/version.html">version</a></li>
           <li<%= sidebar_current("cli-nonprimary") %>><a href="/docs/cli/non-primary.html">More Commands</a></li>
+          <li<%= sidebar_current("cli-aliases") %>><a href="/docs/cli/aliases.html">Aliases</a></li>
           <li<%= sidebar_current("cli-machinereadable") %>><a href="/docs/cli/machine-readable.html">Machine Readable Output</a></li>
         </ul>
       </li>