CODEWITHSUNDEEP
amazon-ec2cloud-init
SimonH
SimonH

Reputation: 984

Is there anyway to access values from the EC2 tags in cloud-init

I know I can access the tags via the metadata and cli tools, but is there anyway to access them whilst running cloud-init? Ideally I'd like to look for a tag called hostname and use it to set the machine host name.

Thanks

Upvotes: 3

Views: 1894

Answers (3)

MATTHEW SILVEUS
MATTHEW SILVEUS

Reputation: 21

As mentioned in a previous answer by tgoodhart AWS has enabled the ability to get tags from the meta data store on an EC2 instance. However in order to have access to this, you will have to launch the EC2 instances with "InstanceMetadataTags" metadata option enabled. Otherwise the EC2 instance will not publish the tags to its meta data store and cloud init will not be able to read the tags. This link gives more information on how to enable this metadata option. https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/Using_Tags.html#work-with-tags-in-IMDS

Upvotes: 1

tgoodhart
tgoodhart

Reputation: 3266

In more recent versions of cloud-init, metadata is available via jinja templates. EC2 also recently started exposing tags via the EC2 instance metadata store. Taken together, you can use this information to retrieve tags as part of your cloud-init.

Example:

cloud-init query -f "{{ds.meta_data.tags.instance}}"

As part of the user data:

## template: jinja
#cloud-config

final_message: |
  My name is {{ds.meta_data.tags.instance.Name}}

Upvotes: 4

Chad Smith
Chad Smith

Reputation: 146

This command can be run from userdata (or any time, really) to access the instance ID from the metadata, and use it to pull the tag called "hostname". You could assign this to a variable, or use the output to directly set the hostname of the instance.

aws ec2 describe-instances --output text --query 'Reservations[*].Instances[*].Tags[?Key==`hostname`].Value' --instance-id `curl -s http://169.254.169.254/latest/meta-data/instance-id`

Upvotes: 2

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