Create a concept of "base" modules that are always installed.

These will not appear in the farmOS modules form, but can be uninstalled
manually if a more customized deployment is desired.

farm.install

@@ -53,6 +53,9 @@ function farm_install_tasks_alter(&$tasks, $install_state) {
  */
 function farm_install_modules(array &$install_state) {
 
+  // Load the list of farmOS core modules.
+  $all = farm_modules();
+
   // Load the list of modules that should be installed.
   // If provided, use the modules defined in farm_install_modules.module
   // profile arguments. We assume this is an array of module machine names,
@@ -62,16 +65,18 @@ function farm_install_modules(array &$install_state) {
     $modules_arg = $install_state['forms']['farm']['modules'];
     if ($modules_arg === 'all') {
       $all = farm_modules();
-      $modules = array_merge(array_keys($all['default']), array_keys($all['optional']));
+      $modules = array_merge(array_keys($all['base']), array_keys($all['default']), array_keys($all['optional']));
     }
     else {
       $modules = Json::decode($modules_arg);
     }
   }
 
   // Use the state set by the \Drupal\farm\Form\FarmModulesForm submit method.
+  // Merge base modules into it.
   else {
     $modules = \Drupal::state()->get('farm.install_modules') ?: [];
+    $modules = array_merge(array_keys($all['base']), $modules);
   }
 
   // If this is running in the context of a functional test, do not install any

farm.profile

@@ -9,12 +9,17 @@
  * Define farmOS modules that can be installed.
  *
  * @return array
- *   Returns an array with two sub-arrays: 'default' and 'optional'. Default
- *   modules will be selected for installation by default, and optional modules
- *   will require the user to select them for installation.
+ *   Returns an array with three sub-arrays: 'base', 'default' and 'optional'.
+ *   Base modules will always be installed, but can be uninstalled. Default and
+ *   optional modules will appear as options during farmOS installation and in
+ *   a form available to admins. During initial farmOS installation, default
+ *   modules will be selected by default, and optional modules will require the
+ *   user to select them for installation.
  */
 function farm_modules() {
   return [
+    'base' => [
+    ],
     'default' => [
       'farm_land' => t('Land assets'),
       'farm_plant' => t('Plant assets'),