/etc/postgresql/9.5/main/pg_hba.conf:
# Database administrative login by Unix domain socket
local all postgres peer
# TYPE DATABASE USER ADDRESS METHOD
# "local" is for Unix domain socket connections only
local all all peer
# IPv4 local connections:
host all all 10.10.30.50/32 md5
host all all 127.0.0.1/32 md5
# IPv6 local connections: