Add new section about how to run commands remotely.

bin/handbook-manifest.json

@@ -113,6 +113,12 @@
         "markdown_source": "https:\/\/github.com\/wp-cli\/handbook\/blob\/master\/release-checklist.md",
         "parent": null
     },
+    "running-commands-remotely": {
+        "title": "Running Commands Remotely",
+        "slug": "running-commands-remotely",
+        "markdown_source": "https:\/\/github.com\/wp-cli\/handbook\/blob\/master\/running-commands-remotely.md",
+        "parent": null
+    },
     "roadmap": {
         "title": "Roadmap",
         "slug": "roadmap",
@@ -347,4 +353,4 @@
         "markdown_source": "https:\/\/github.com\/wp-cli\/handbook\/blob\/master\/internal-api\/wp-cli-warning.md",
         "parent": "internal-api"
     }
-}
+}

index.md

@@ -8,6 +8,7 @@ Can’t find what you’re looking for? [Open an issue](https://github.com/wp-cl
 
 * **[Installing](https://make.wordpress.org/cli/handbook/installing/)** - Recommended and alternative installation mechanisms.
 * **[Quick start](https://make.wordpress.org/cli/handbook/quick-start/)** - Where to begin after you've installed WP-CLI for the first time.
+* **[Running commands remotely](https://make.wordpress.org/cli/handbook/running-commands-remotely/)** - Learn how to remotely control multiple servers at once. 
 * **[Commands cookbook](https://make.wordpress.org/cli/handbook/commands-cookbook/)** - The full 101 how commands work, writing your own, and sharing them with the world.
 * **[Common issues and their fixes](https://make.wordpress.org/cli/handbook/common-issues/)** - In case of fire, break glass.
 * **[External resources](https://make.wordpress.org/cli/handbook/external-resources/)** - Blog posts, slides and videos from users.

running-commands-remotely.md

@@ -0,0 +1,132 @@
+# Running Commands Remotely
+
+## Using an SSH connection
+
+WP-CLI accepts an `--ssh=<host>` global parameter for running a command against a remote WordPress install.
+
+Under the hood, WP-CLI proxies commands to the ssh executable, which then passes them to WP-CLI installed on the remote machine. Your syntax for `--ssh=<host>` can be any of the following:
+
+* Just the host (e.g. `wp --ssh=runcommand.io`), which means the user will be inferred from your current system user, and the path will be the SSH user’s home directory.
+* The user and the host (e.g. `wp [email protected]`).
+* The user, the host, and the path to the WordPress install (e.g. `wp [email protected]~/webapps/production`). The path comes immediately after the TLD of the host.
+* A known alias, stored in `~/.ssh/config` (e.g. `wp --ssh=rc` for the `@rc` alias).
+
+**Note: you need to have a copy of WP-CLI installed on the remote server, accessible as `wp`.**
+
+Futhermore, `--ssh=<host>` won’t load your `~/.bash_profile` if you have a shell alias defined, or are extending the `$PATH` environment variable. If this affects you, [here’s a more thorough explanation](https://make.wordpress.org/cli/handbook/running-commands-remotely/#making-wp-cli-accessible-on-a-remote-server) of how you can make `wp` accessible.
+
+## Aliases
+
+WP-CLI aliases are shortcuts you register in your `wp-cli.yml` or `config.yml` to effortlessly run commands against any WordPress install.
+
+For instance, when you are working locally, have registered a new rewrite rule and need to flush rewrites inside of your Vagrant-based virtual machine, you can run:
+
+```
+# Run the flush command on the development environment
+$ wp @dev rewrite flush
+Success: Rewrite rules flushed.
+```
+
+Then, once the code goes to production, you can run:
+
+```
+# Run the flush command on the production environment
+$ wp @prod rewrite flush
+Success: Rewrite rules flushed.
+```
+
+You don't need to SSH into machines, change directories, and generally spend a full minute to get to a given WordPress install, you can just let WP-CLI know what machine to work with and it knows how to make the actual connection.
+
+Additionally, alias groups let you register groups of aliases. If I want to run a command against both configured example sites, I can use a group like `@both`:
+
+```
+# Run the update check on both environments
+$ wp @both core check-update
+Success: WordPress is at the latest version.
+Success: WordPress is at the latest version.
+```
+
+Aliases can be registered in your project’s `wp-cli.yml` file, or your user’s global `~/.wp-cli/config.yml` file:
+
+```yaml
+@prod:
+  ssh: [email protected]~/webapps/production
+@dev:
+  ssh: [email protected]/srv/www/example.dev
+@both:
+  - @prod
+  - @dev
+```
+
+You can find more information about how to set up your configuration files in the [Config section](https://make.wordpress.org/cli/handbook/config/#config-files).
+
+## Running custom commands remotely
+
+If you want to run a custom command on a remote server, that custom command needs to be installed on the remote server, but it does not have to be installed on the local machine you're launching `wp` from.
+
+You can use the WP-CLI package manager remotely to install custom commands to remote machines.
+
+Example:
+
+```
+# The command is not installed on either local or remote machine
+$ wp db ack
+Error: 'ack' is not a registered subcommand of 'db'. See 'wp help db'.
+$ wp @dev db ack
+Error: 'ack' is not a registered subcommand of 'db'. See 'wp help db'.
+
+# To make the command work on the remote machine, we can install it remotely
+# through the WP-CLI package manager
+$ wp @dev package install runcommand/db-ack
+Installing package runcommand/db-ack (dev-master)
+Updating /home/vagrant/.wp-cli/packages/composer.json to require the package...
+Using Composer to install the package...
+---
+Loading composer repositories with package information
+Updating dependencies
+Resolving dependencies through SAT
+Dependency resolution completed in 0.311 seconds
+Analyzed 4726 packages to resolve dependencies
+Analyzed 162199 rules to resolve dependencies
+Package operations: 1 install, 0 updates, 0 removals
+Installs: runcommand/db-ack:dev-master aff8ccc
+ - Installing runcommand/db-ack (dev-master aff8ccc)
+Writing lock file
+Generating autoload files
+---
+Success: Package installed.
+
+# Now we can run the command remotely, even though it is not installed locally
+$ wp @dev db ack [email protected]
+wp_users:user_email
+9:[email protected]
+```
+
+## Making WP-CLI accessible on a remote server
+
+Running a command remotely through SSH requires having `wp` accessible on the `$PATH` on the remote server. Because SSH connections don’t load `~/.bashrc` or `~/.zshrc`, you may need to specify a custom `$PATH` when using `wp --ssh=<host>`.
+
+You can do so by hooking into the `before_ssh` hook, and defining an environment variable with the command you’d like to run:
+
+```php
+WP_CLI::add_hook( 'before_ssh', function() {
+
+    $host = WP_CLI\Utils\parse_ssh_url(
+        WP_CLI::get_runner()->config['ssh'],
+        PHP_URL_HOST
+    );
+
+    switch( $host ) {
+        case 'runcommand.io':
+            putenv( 'WP_CLI_SSH_PRE_CMD=export PATH=$HOME/bin:$PATH' );
+            break;
+    }
+} );
+```
+
+If you put the code above in a `pre-ssh.php` file, you can load it for your entire environment by requiring it from your `~/.wp-cli/config.yml` file:
+
+```yaml
+require:
+  - pre-ssh.php
+```