How to get the instance Name from the instance in AWS? - bash

Question

I'm trying to set up a means to register an instance in route53 automatically when the instance is created, using salt and this article.
The article uses ec2-metadata to get the instance-id and and the hostname. I'm wondering if there is a way, using bash within the instance, to get the instance Name instead. ec2-metadata only seems to show the instance-id. Thanks in advance.

Answer 1

First, you need to get the instance-id.
AWS_INSTANCE_ID=`curl -s http://169.254.169.254/latest/meta-data/instance-id`
Than you can get the ec2 instance name using below command.
EC2_NAME=$(aws ec2 describe-tags --region $REGION --filters "Name=resource-id,Values=$AWS_INSTANCE_ID" "Name=key,Values=Name" --output text | cut -f5)
Please ensure that you have AWS Cli Installed.
I hope this helps.
Thanks!

Answer 2

First and foremost, the Amazon EC2 Instance Metadata Service also provides quite some other Names besides the instance-id, if these might be what you are looking for - see Instance Metadata Categories:
hostname - The private hostname of the instance. In cases where multiple network interfaces are present, this refers to the eth0 device (the device for which the device number is 0).
local-hostname - The private DNS hostname of the instance. In cases where multiple network interfaces are present, this refers to the eth0 device (the device for which the device number is 0).
public-hostname - The instance's public DNS. If the instance is in a VPC, this category is only returned if the enableDnsHostnames attribute is set to true.
If you are looking for the Name as exposed in the AWS Management Console though, you would indeed need to resort to using one of the Tools for Amazon Web Services to retrieve it - that Name is in fact just a regular tag with the key Name (see Tagging Your Amazon EC2 Resources), which happens to be used across most AWS services for the obvious purpose.
Here's how to get it with the AWS Command Line Interface for example (skipping region and credentials):
aws ec2 describe-tags \
--filters Name=resource-id,Values=i-abcd1234 Name=key,Values=Name \
--query Tags[].Value --output text
For more advanced CLI JSON output processing than what's possible with the built in --query option, you could resort to jq (a lightweight and flexible command-line JSON processor).
Overthink's answer provides an example based on the now legacy Amazon EC2 API Tools (please note the comments, which correctly point out that you'd nowadays deal with credentials differently, see Tell the CLI Tools Who You Are and IAM Roles for EC2 instances for details).

Answer 3

Not sure what it would look like with bash, but you could use an SDK from the instance itself if you can get the instance id. You would query the ec2 recourse and pass in the ec2 instance id. Using the ruby sdk it would look like:
i = ec2.instances["i-12345678"]
puts i.dns_name

Answer 4

Found that describe-tags not working in my config, failed with 'UnauthorizedOperation' error. Got this working with describe-instances:
aws ec2 describe-instances --filters Name=instance-id,Values=$(wget -qO- http://instance-data/latest/meta-data/instance-id) --query Reservations[].Instances[].Tags[].Value --output text
Command using region and access keys from current user's aws config file's [default] section: ~/.aws/config . If need to use another user's region/keys (can be found at AWS console's IAM dashboard), you can add them to another section in that file, for example [user2] and use in command like this:
aws --profile user2 ec2 describe-instances --filters Name=instance-id,Values=$(wget -qO- http://instance-data/latest/meta-data/instance-id) --query Reservations[].Instances[].Tags[].Value --output text

Answer 5

Use this command to show which metadata is available
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/
You can chain any one of the below file/folders to display the required info
ami-id
ami-launch-index
ami-manifest-path
block-device-mapping/
events/
hostname
iam/
identity-credentials/
instance-action
instance-id
instance-life-cycle
instance-type
local-hostname
local-ipv4
mac
metrics/
network/
placement/
profile
public-keys/
reservation-id
For eg. instance-type can be chained this to the above command as follows:
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/instance-type
Reference from AWS

Answer 6

ec2metadata tool is useful to get information about the EC2 server.
You can use the following;
ec2metadata --instance-id
in bash;
INSTANCE_ID=$(ec2metadata --instance-id)
You can also access other useful information like the following;
--ami-id
--ami-launch-index
--ami-manifest-path
--ancestor-ami-ids
--availability-zone
--block-device-mapping
--instance-action
--instance-id
--instance-type
--local-hostname
--local-ipv4
--kernel-id
--mac
--profile
--product-codes
--public-hostname
--public-ipv4
--public-keys
--ramdisk-id
--reserveration-id
--security-groups