Running Drupal Multisite on Lando

Drupal multisite is a feature of Drupal that allows you to run multiple Drupal installs off of a common codebase. It's common in universities and other settings where you might want to share themes and modules between a collection of many websites.

Configuring Lando

To run Drupal multisite you need to do several things:

1. Your .lando.yml will need proxies for each multisite in the appserver array
2. The settings.local.php file within your subsite directory (ex: docroot/sites/site1/) needs settings to connect to the appropriate Lando-hosted database.
3. You need Drush aliases pointing to your local. If you use Drupal console, you'll need to specify your uri (ex: drupal --uri=http://site1.lndo.site cr all).

1. Configure .lando.yml

Create proxies for each multisite in the appserver array in your .lando.yml file. Ex:

proxy:
  appserver:
    - site1.lndo.site
    - site2.lndo.site
services:
  site1:
    type: mysql:5.7
    portforward: 33068
    config:
      confd: .lando/mysql/conf.d
  site2:
    type: mysql:5.7
    portforward: 33069
    config:
      confd: .lando/mysql/conf.d

2. Configure each subsite's settings.local.php

Configure each subsite to include the default Lando config to connect to the database, along with specifying the appserver name you defined in .lando.yml. For example, in docroot/sites/site1/settings/settings.local.php you would include...

/**
 * Database configuration.
 */
$databases['default'] = array (
  'default' => array (
    'driver' => 'mysql',
    'database' => 'database',
    'username' => 'mysql',
    'password' => 'password',
    'prefix' => '',
    'port' => 3306,
  )
);
// The only thing to add from the out-of-the-box Lando db is the special host for each subsite
$databases['default']['default']['host'] = 'site1';

If you're on Acquia...

You must specify $_SERVER['PWD']=DRUPAL_ROOT if you use Drush 9 on Acquia (this may apply to some other hosts as well). Update your main sites/default/settings.php to tell our local Drupal to use the /settings/settings.local.php within each subsite:

if (!key_exists('AH_SITE_ENVIRONMENT', $_ENV)) {
  $environment_settings = __DIR__  . '/settings/settings.local.php';
  if (file_exists($environment_settings)) {
    include $environment_settings;
  }
}
// Temporary fix because drush9 blocks superglobals
$_SERVER['PWD']=DRUPAL_ROOT;

3. Define Drush aliases for each subsite

Finally you'll need some Drush aliases so Drush can find your subsite installs. Here docroot is where our Drupal root is. For example, in site_root/drush/sites/site-aliases/site1.site.yml we would define...

local:
  uri: 'https://site1.lndo.site'
  paths:
  - files: /path_to_your_local_site/site_root/docroot'
dev:
  host: 'site1dev.ssh.prod.acquia-sites.com'
  user: 'site1.dev'
  root: '/var/www/html/site1.dev/docroot'
  uri: 'site1dev.prod.acquia-sites.com'
  ac-site: 'site1'
  ac-env: 'dev'
  ac-realm: 'prod'
  paths:
    drush-script: 'drush8'
test:
  root: '/var/www/html/site1.test/docroot'
  ac-site: 'site1'
  ac-env: 'test'
  ac-realm: 'prod'
  uri: 'site1stg.prod.acquia-sites.com'
  host: 'site1stg.ssh.prod.acquia-sites.com'
  user: 'site1.test'
  paths:
    drush-script: 'drush8'
prod:
  root: '/var/www/html/site1.prod/docroot'
  ac-site: 'site1'
  ac-env: 'prod'
  ac-realm: 'prod'
  uri: 'site1.prod.acquia-sites.com'
  host: 'site1.ssh.prod.acquia-sites.com'
  user: 'site1.prod'
  paths:
    drush-script: 'drush8'

I'm using drush8 against the cloud here by specifying that in the drush-script, since I've had issues trying to use drush9 and have no defined drush9 aliases, but that's purely a concern of working with Acquia Cloud.