Creating a Mongodb replicaset in an AWC VPC

Question

I'm creating my mongo cluster inside a VPC. The issue I have is that the privately assigned hostname is unresolvable.

An instance is assigned an ip address 10.0.10.20. Its hostname will be ip-10-0-10-20.

[ec2-user@ip-10-0-10-20 ~]$ ping ip-10-0-10-20
ping: unknown host ip-10-0-10-20

If I add an entry to /etc/hosts (127.0.0.1 ip-10-0-10-20):

ping ip-10-0-10-20
PING ip-10-0-10-20 (127.0.0.1) 56(84) bytes of data.
64 bytes from localhost (127.0.0.1): icmp_seq=1 ttl=64 time=0.027 ms

However, each of my nodes are built from the same AMI. I would need to customise each node as it is created with that nodes ip address in the /etc/hosts file.

There's a possibility of putting a command into a launch script but I can't seem to get it to work. The command line equivalent of adding a line to the end of a file keeps giving me permission problems:

[ec2-user@ip-10-0-10-20 ~]$ sudo echo 127.0.0.1 ip-10-0-10-20 >> /etc/hosts -bash: /etc/hosts: Permission denied

I'm not even sure this is the right approach for Mongo inside a VPC.

Any help appreciated.

Answer 1

see "Updating DNS Support for Your VPC" at http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/vpc-dns.html

It's likely your VPC was created before the DNS Hostname support flag was available. Set it to True.