title: Can't connect to RDS through EC2
body: <p>I'm trying to access an RDS instance from an EC2 instance but with no luck. I'm able to connect to RDS from pgAdmin without any problem, but I'm try to connect to it from EC2 using psql I get the following error:</p>
  
  <pre><code>psql: could not translate host name "pgrds.cqvae2m3k8q9.us-west-2.rds.amazonaws.com" to address: Name or service not known
  </code></pre>
  
  <p>I have both instances running in the same VPC and using the same security group, which have all traffic open both ways. I've spent quite some time on this, and tried several solutions but none worked.</p>