文档:
http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/vpc-dns.html段落:
we provide the instance with a public DNS hostname only if DNS hostnames are enabled for the VPC. By default, DNS hostnames are enabled only for default VPCs and VPCs that you create using the VPC wizard in the VPC console.
而我的 VPC 是在创建 EC2 instances 的时候“顺手”创建的,所以默认没开启
enableDnsHostnames
Indicates whether the instances launched in the VPC get DNS hostnames. If this attribute is true, instances in the VPC get DNS hostnames; otherwise, they do not. If you want your instances to get DNS hostnames, you must also set the enableDnsSupport attribute to true.
去 VPC 的控制面板,右键点那个 VPC ,然后菜单里选 Edit DNS hostnames ,在小窗口里开启该功能即可
不过 PTR 记录是依然没有的