I’m pretty sure I installed Drush 8 correctly on Windows 10. I ran the command window as administrator. I changed to my Drupal directory, but I get “Command pm-update needs a higher bootstrap level to run – you will need to invoke drush from a more functional Drupal environment to run this command. The drush command ‘pm-update’ could not be executed. Drush was not able to start (bootstrap) the Drupal database. Following are all the messages & commands I entered.

ColorConsole [Version 2.4.2000 ] Microsoft Windows [Version 10.0.14393] (c)        2016 Microsoft Corporation. All rights reserved. C:UserssamstDownloads>cd C:xampphtdocsD8 C:xampphtdocsD8>drush status Drupal version : 8.2.4 Site URI : http://default Database driver : mysql Database hostname : localhost Database port : Database username : root Database name : d8 PHP configuration : C:xamppphpphp.ini PHP OS : WINNT Drush script : C:/Users/samst/AppData/Roaming/Composer/vendor/drush/drush/drush.php Drush version : 8.1.5 Drush temp directory : C:UserssamstAppDataLocalTemp Drush configuration : Drush alias files : Drupal root : C:xampphtdocsD8 Drupal Settings File : sites/default/settings.php Site path : sites/default Sync config path : sites/default/files/config_zKz1ApBZ7jZluMMX-WwnTZyMM0eVUEH6DkWwb6HxM_V0Y0izLCsKyaGVKs7EDZiAE FFWlaSJ4g/sync C:xampphtdocsD8>drush drush pm-update The drush command 'drush pm-update' could not be found. Run drush cache-clear drush to clear the [error] commandfile cache if you have installed new extensions. Drush was not able to start (bootstrap) the Drupal database. [error] Hint: This may occur when Drush is trying to: * bootstrap a site that has not been installed or does not have a configured database. In this case you can select another site with a working database setup by specifying the URI to use with the --uri parameter on the command line. See drush topic docs-aliases for details. * connect the database through a socket. The socket file may be wrong or the php-cli may have no access to it in a jailed shell. See http://drupal.org/node/1428638 for details. Drush was attempting to connect to: Drupal version : 8.2.4 Site URI : http://default Database driver : mysql Database hostname : localhost Database port : Database username : root Database name : d8 PHP configuration : C:xamppphpphp.ini PHP OS : WINNT Drush script : C:/Users/samst/AppData/Roaming/Composer/vendor/drush/drush/drush.php Drush version : 8.1.5 Drush temp directory : C:UserssamstAppDataLocalTemp Drush configuration : Drush alias files : Drupal root : C:xampphtdocsD8 Drupal Settings File : sites/default/settings.php Site path : sites/default Sync config path : sites/default/files/config_zKz1ApBZ7jZluMMX-WwnTZyMM0eVUEH6DkWwb6HxM_V0Y0izLCsKy aGVKs7EDZiAEFFWlaSJ4g/sync C:xampphtdocsD8>drush cache-clear drush 'drush' cache was cleared. [success] C:xampphtdocsD8>drush pm-update Command pm-update needs a higher bootstrap level to run - you will need to invoke drush from a more [error] functional Drupal environment to run this command. The drush command 'pm-update' could not be executed. [error] Drush was not able to start (bootstrap) the Drupal database. [error] Hint: This may occur when Drush is trying to: * bootstrap a site that has not been installed or does not have a configured database. In this case you can select another site with a working database setup by specifying the URI to use with the --uri parameter on the command line. See drush topic docs-aliases for details. * connect the database through a socket. The socket file may be wrong or the php-cli may have no access to it in a jailed shell. See http://drupal.org/node/1428638 for details. Drush was attempting to connect to: Drupal version : 8.2.4 Site URI : http://default Database driver : mysql Database hostname : localhost Database port : Database username : root Database name : d8 PHP configuration : C:xamppphpphp.ini PHP OS : WINNT Drush script : C:/Users/samst/AppData/Roaming/Composer/vendor/drush/drush/drush.php Drush version : 8.1.5 Drush temp directory : C:UserssamstAppDataLocalTemp Drush configuration : Drush alias files : Drupal root : C:xampphtdocsD8 Drupal Settings File : sites/default/settings.php Site path : sites/default Sync config path : sites/default/files/config_zKz1ApBZ7jZluMMX-WwnTZyMM0eVUEH6DkWwb6HxM_V0Y0izLCsKy aGVKs7EDZiAEFFWlaSJ4g/sync C:xampphtdocsD8> 

I am running D8 with XAMPP on Windows 10. I’ve spent a significant amount of time searching the web for a solution. I tried changing the ‘host’ line in settings.php. That did not help.