xdebug on vagrant

Outside the VM
  In PHPStorm,
    Run => Start Listening for PHP Connections
    Run => Break at first line in PHP scripts

Inside the VM
  Navigate to docroot and run:
  XDEBUG_CONFIG="idekey=phpstorm remote_host=`netstat -rn | grep "^0.0.0.0 " | tr -s ' ' | cut -d " " -f2`" php -dzend_extension=xdebug.so -d xdebug.remote_enable=1 ../vendor/bin/drush st
    
    Sets the XDEBUG_CONFIG environment variable. The value has two components:
      idekey - not clear if this is needed
      remote_host - The value is the IP address of the host machine. This tells the VM's PHP how to connect back to your PHPStorm. The value is dynamically figured out by netstat. See this Stack Overflow post.
    Calls php with options that load xdebug extension (already present in the VM) and enables xdebug's remote debugging.
    Pass the drush script as first argument to php. In this example, we run Drush's st command.