Drupal Console provides two types of commands, stand alone and container aware commands.
Stand alone commands: These commands can run outside of a Drupal 8 site root.
Container aware commands: These commands must be run within a Drupal 8 site root.
You can run Drupal Console form any directory on your system by using the --root option to define the Drupal root to be use in the command execution.
$ drupal --root=/var/www/drupal8.dev cr all
NOTE: Possible messages when executing Drupal Console outside a Drupal site root and no --root option provided.
When running the project outside of a Drupal 8 site root, the following message will be shown.
In order to list all of the available commands, you should run this inside a drupal root directory.
When running the project within of a Drupal 8 site root, but site is not yet installed, the following message will be shown.
In order to list all of the available commands you should install drupal first.