Query EC2 tags from within instance

You can alternatively use the describe-instances cli call rather than describe-tags:

This example shows how to get the value of tag 'my-tag-name' for the instance:

aws ec2 describe-instances \
  --instance-id $(curl -s http://169.254.169.254/latest/meta-data/instance-id) \
  --query "Reservations[*].Instances[*].Tags[?Key=='my-tag-name'].Value" \
  --region ap-southeast-2 --output text

Change the region to suit your local circumstances. This may be useful where your instance has the describe-instances privilege but not describe-tags in the instance profile policy

I have pieced together the following that is hopefully simpler and cleaner than some of the existing answers and uses only the AWS CLI and no additional tools.

This code example shows how to get the value of tag 'myTag' for the current EC2 instance:

Using describe-tags:

export AWS_DEFAULT_REGION=us-east-1
instance_id=$(curl -s http://169.254.169.254/latest/meta-data/instance-id)
aws ec2 describe-tags \
  --filters "Name=resource-id,Values=$instance_id" 'Name=key,Values=myTag' \
  --query 'Tags[].Value' --output text

Or, alternatively, using describe-instances:

aws ec2 describe-instances --instance-id $instance_id \
  --query 'Reservations[].Instances[].Tags[?Key==`myTag`].Value' --output text

A variation on some of the answers above but this is how I got the value of a specific tag from the user-data script on an instance

REGION=$(curl http://instance-data/latest/meta-data/placement/availability-zone | sed 's/.$//')

INSTANCE_ID=$(curl -s http://instance-data/latest/meta-data/instance-id)

TAG_VALUE=$(aws ec2 describe-tags --region $REGION --filters "Name=resource-id,Values=$INSTANCE_ID" "Name=key,Values='<TAG_NAME_HERE>'" | jq -r '.Tags[].Value')

Using the AWS 'user data' and 'meta data' APIs its possible to write a script which wraps puppet to start a puppet run with a custom cert name.

First start an aws instance with custom user data: 'role:webserver'

#!/bin/bash

# Find the name from the user data passed in on instance creation
USER=$(curl -s "http://169.254.169.254/latest/user-data")
IFS=':' read -ra UDATA <<< "$USER"

# Find the instance ID from the meta data api
ID=$(curl -s "http://169.254.169.254/latest/meta-data/instance-id")
CERTNAME=${UDATA[1]}.$ID.aws

echo "Running Puppet for certname: " $CERTNAME
puppet agent -t --certname=$CERTNAME 

This calls puppet with a certname like 'webserver.i-hfg453.aws' you can then create a node manifest called 'webserver' and puppets 'fuzzy node matching' will mean it is used to provision all webservers.

This example assumes you build on a base image with puppet installed etc.

Benefits:

1) You don't have to pass round your credentials

2) You can be as granular as you like with the role configs.

Jq + ec2metadata makes it a little nicer. I'm using cf and have access to the region. Otherwise you can grab it in bash.

aws ec2 describe-tags --region $REGION \
--filters "Name=resource-id,Values=`ec2metadata --instance-id`" | jq --raw-output \
'.Tags[] | select(.Key=="TAG_NAME") | .Value'

No jq.

aws ec2 describe-tags --region us-west-2 \
--filters "Name=resource-id,Values=`ec2-metadata --instance-id | cut -d " " -f 2`" \
--query 'Tags[?Key==`Name`].Value' \
--output text

Starting January 2022, this should be also available directly via ec2 metadata api (if enabled).

curl http://169.254.169.254/latest/meta-data/tags/instance

https://aws.amazon.com/about-aws/whats-new/2022/01/instance-tags-amazon-ec2-instance-metadata-service/

The Metadata tool seems to no longer be available, but that was an unnecessary dependency anyway.

Follow the AWS documentation to have the instance's profile grant it the "ec2:DescribeTags" action in a policy, restricting the target resources as much as you wish. (If you need a profile for another reason then you'll need to merge policies into a new profile-linked role).

Then:

aws --region $(curl -s http://169.254.169.254/latest/meta-data/placement/availability-zone  | sed -e 's/.$//') ec2 describe-tags --filters Name=resource-type,Values=instance Name=resource-id,Values=$(curl http://169.254.169.254/latest/meta-data/instance-id) Name=key,Values=Name |
perl -nwe 'print "$1\n" if /"Value": "([^"]+)/;'

Well there are lots of good answers here but none quite worked for me exactly out of the box, I think the CLI has been updated since some of them and I do like using the CLI. The following single command works out of the box for me in 2021 (as long as the instance's IAM role is allowed to describe-tags).

aws ec2 describe-tags \
--region "$(ec2-metadata -z | cut -d' ' -f2 | sed 's/.$//')" \
--filters "Name=resource-id,Values=$(ec2-metadata --instance-id | cut -d " " -f 2)" \
--query 'Tags[?Key==`Name`].Value' \
--output text

For those crazy enough to use Fish shell on EC2, here's a handy snippet for your /home/ec2-user/.config/fish/config.fish. The hostdata command now will list all your tags as well as the public IP and hostname.

set -x INSTANCE_ID (wget -qO- http://instance-data/latest/meta-data/instance-id)
set -x REGION (wget -qO- http://instance-data/latest/meta-data/placement/availability-zone | sed 's/.$//')

function hostdata
    aws ec2 describe-tags --region $REGION --filter "Name=resource-id,Values=$INSTANCE_ID" --output=text | sed -r 's/TAGS\t(.*)\t.*\t.*\t(.*)/\1="\2"/'
    ec2-metadata | grep public-hostname
    ec2-metadata | grep public-ipv4
end

AWS has recently announced support for instance tags in Instance Metadata Service: https://aws.amazon.com/about-aws/whats-new/2022/01/instance-tags-amazon-ec2-instance-metadata-service/

If you have have the tag metadata option enabled for an instance, you can simply do

$ TOKEN=`curl -X PUT "http://169.254.169.254/latest/api/token" -H "X-aws-ec2-metadata-token-ttl-seconds: 900"`
$ curl -H "X-aws-ec2-metadata-token: $TOKEN" -v http://169.254.169.254/latest/meta-data/tags/instance

It is possible to get Instance tags from within the instance via metadata.

First, allow access to tags in instance metadata as explained here

Then, run this command for IMDSv1, Refer

curl http://169.254.169.254/latest/meta-data/tags/instance/Name

or this command for IMDSv2

TOKEN=`curl -X PUT "http://169.254.169.254/latest/api/token" -H "X-aws-ec2-metadata-token-ttl-seconds: 21600"` \
&& curl -H "X-aws-ec2-metadata-token: $TOKEN" -v http://169.254.169.254/latest/meta-data/tags/instance