$ sudo -u postgres psql postgres
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
	LANGUAGE = "en_US:en",
	LC_ALL = (unset),
	LC_PAPER = "fi_FI.UTF-8",
	LC_ADDRESS = "fi_FI.UTF-8",
	LC_MONETARY = "fi_FI.UTF-8",
	LC_NUMERIC = "fi_FI.UTF-8",
	LC_TELEPHONE = "fi_FI.UTF-8",
	LC_IDENTIFICATION = "fi_FI.UTF-8",
	LC_MEASUREMENT = "fi_FI.UTF-8",
	LC_TIME = "fi_FI.UTF-8",
	LC_NAME = "fi_FI.UTF-8",
	LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
psql: could not connect to server: No such file or directory
	Is the server running locally and accepting
	connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?