Sometimes you want to retrieve EC2 insntances' region information.
You can query that information through instance metadata(169.254.169.254).
$ curl --silent http://169.254.169.254/latest/dynamic/instance-identity/document
{
"privateIp" : "172.31.2.15",
"instanceId" : "i-12341ee8",
"billingProducts" : null,
"instanceType" : "t2.small",
"accountId" : "1234567890",
"pendingTime" : "2015-11-03T03:09:54Z",
"imageId" : "ami-383c1956",
"kernelId" : null,
"ramdiskId" : null,
"architecture" : "x86_64",
"region" : "ap-northeast-1", # <- region
"version" : "2010-08-31",
"availabilityZone" : "ap-northeast-1c",
"devpayProductCodes" : null
}
Response's JSON has a region key, so if you just want to get region, filter the key with jq.
$ sudo yum install -y jq
$ curl --silent http://169.254.169.254/latest/dynamic/instance-identity/document | jq -r .region
ap-northeast-1
Even if you launch an EC2 instance with IAM role, you can't run commands without supplying region info. Otherwise, you'll encounter errors as follows.
$ aws ec2 describe-vpcs
You must specify a region. You can also configure your region by running "aws configure".
Here's how to set aws-cli's region.
First, check the curren settings.
$ aws configure list
Name Value Type Location
---- ----- ---- --------
profile <not set> None None
access_key ****************GVKA iam-role
secret_key ****************bll+ iam-role
region <not set> None None
region is not set.
Now pass metadata's region to aws configure set region command.
$ aws configure set region `curl --silent http://169.254.169.254/latest/dynamic/instance-identity/document | jq -r .region`
$ aws configure get region
ap-northeast-1
$ aws configure list
Name Value Type Location
---- ----- ---- --------
profile <not set> None None
access_key ****************GVKA iam-role
secret_key ****************bll+ iam-role
region ap-northeast-1 config-file ~/.aws/config
$ cat ~/.aws/config
[default]
region = ap-northeast-1
To configure API region, just add following code to you UserData.
#!/bin/bash
yum install -y jq
REGION=`curl -s http://169.254.169.254/latest/dynamic/instance-identity/document | jq .region -r`
sudo -u ec2-user aws configure set region $REGION