PDOException SQLSTATE[HY000] [2002] No such file or directory

I believe that I've successfully deployed my (very basic) site to fortrabbit, but as soon as I connect to SSH to run some commands (such as `php artisan migrate` or `php artisan db:seed`) I get an error message: [PDOException] SQLSTATE[HY000] [2002] No such file or directory At some point the migration must have worked, because my tables are there - but this doesn't explain why it isn't working for me now.