Find region from within an EC2 instance

Question

Is there a way to look up the region of an instance from within the instance?

I\'m looking for something similar to the method of finding the instance id.

Answer 1

If you are looking to get region using JS, this should work :

meta.request("/latest/meta-data/placement/availability-zone",function(err,data){
        if(err)
                console.log(err);
        else{
                console.log(data);
                str = data.substring(0, data.length - 1);
                AWS.config.update({region:str});
                ec2 = new AWS.EC2();
            }
     });

This was the mapping found from AWS DOCS, in response to metadata API call, just trim the last character should work.

  eu-west-1a :eu-west-1
  eu-west-1b :eu-west-1
  eu-west-1c :eu-west-1
  us-east-1a :us-east-1
  us-east-1b :us-east-1
  us-east-1c :us-east-1
  us-east-1d :us-east-1
  ap-northeast-1a :ap-northeast-1
  ap-northeast-1b :ap-northeast-1
  us-west-1a :us-west-1
  us-west-1b :us-west-1
  us-west-1c :us-west-1
  ap-southeast-1a :ap-southeast-1
  ap-southeast-1b :ap-southeast-1

Answer 2

If you are OK with using jq, you can run the following:

curl -s http://169.254.169.254/latest/dynamic/instance-identity/document | jq .region -r

I guess it's the cleanest way.

Answer 3

very simple one liner

export AVAILABILITY_ZONE=`wget -qO- http://instance-data/latest/meta-data/placement/availability-zone`
export REGION_ID=${AVAILABILITY_ZONE:0:${#AVAILABILITY_ZONE} - 1}

Answer 4

Thanks to https://unix.stackexchange.com/a/144330/135640, with bash 4.2+ we can just strip the last char from the availability zone:

$ region=`curl -s 169.254.169.254/latest/meta-data/placement/availability-zone`
$ region=${region::-1}
$ echo $region
us-east-1

This assumes AWS continues to use a single character for availability zones appended to the region.