AWS error - sudo: unable to resolve host ip-10-0-xx-xx

You should enable the DNS hostnames on your VPC: http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/vpc-dns.html#vpc-dns-updating

If for some reason, you cannot enable it, you can still use the /etc/hosts to make it resolve, but this is definitely not the recommended solution

10.0.xx.xx ip-10-0-xx-xx

This worked for me:

Add the following line to /etc/hosts

127.0.0.1 ip-xxx-xx-x-xx

The ip thing is your private ip address

This issue is caused by not enabling enableDnsHostnames in your VPC configuration.

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.

http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/vpc-dns.html#vpc-dns-updating

Can patch easily from command line as follows:

sudo sed -i /etc/hosts -e "s/^127.0.0.1 localhost$/127.0.0.1 localhost $(hostname)/"

And checked that a reboot, or stop, then start the aws instance would preserve it. In case it is lost, can easily re-apply on boot, and can be added to any provision for new vms.

Example

Before:

ubuntu@ip-177-11-22-333:~$ sudo id
sudo: unable to resolve host ip-177-11-22-333
uid=0(root) gid=0(root) groups=0(root)

Fix:

ubuntu@ip-177-11-22-333:~$ sudo sed -i /etc/hosts -e "s/^127.0.0.1 localhost$/127.0.0.1 localhost $(hostname)/"
sudo: unable to resolve host ip-177-11-22-333

After:

ubuntu@ip-177-11-22-333:~$ sudo id
uid=0(root) gid=0(root) groups=0(root)
ubuntu@ip-177-11-22-333:~$