Customize EC2 hostname

ec2-custom-name.sh

#!/usr/bin/env bash
# set hostname to current name with the last 4 chars of instance id
#
id=$(ec2metadata --instance-id)
myname=${HOSTNAME}-${id:(-4)}
hostnamectl set-hostname $myname
sed -i "s/${HOSTNAME}/${myname}/g" /etc/hosts
echo "New hostname is $myname"

ec2-tag-name.sh

#!/usr/bin/env bash
#
# Set EC2 tag Name to the current HOSTNAME of the instance
#
# Required policy:
#
# {
#    "Version": "2012-10-17",
#    "Statement": [
#        {
#            "Sid": "VisualEditor0",
#            "Effect": "Allow",
#            "Action": [
#                "ec2:DeleteTags",
#                "ec2:DescribeTags",
#                "ec2:CreateTags"
#            ],
#            "Resource": "*"
#        }
#    ]
# }
#
# Add this to the IAM Role of the EC2 host and this script will run smoothly!
#

# set -ex

if [[ -z $HOSTNAME ]]; then
  echo "ERROR, cannot procede without a valid HOSTNAME"
  exit 1
fi

region=$(http http://169.254.169.254/latest/dynamic/instance-identity/document | jq -c -r .region)
if [[ -z $region ]]; then
  echo "ERROR, cannot get region info from metatags, am I an EC2 instance? Are httpie and jq installed?"
  exit 2
fi

id=$(http http://169.254.169.254/latest/meta-data/instance-id)

if [[ ! -f ~/.aws/config ]]; then
  [[ ! -d ~/.aws ]] && mkdir ~/.aws

  echo -e "[default]\nregion = $region\n" > ~/.aws/config
  echo "* Configured aws-cli with default region '$region'"
fi

echo "* Getting current tags..."
echo 
if aws ec2 describe-tags --filters "Name=resource-id,Values=$id"; then
  echo 
else
  echo "ERROR, cannot list tags on instance '$id', is there a policy that allow action ec2:DescribeTags in the instance ROLE?"
  exit 3
fi

if aws ec2 delete-tags --resource "$id" --tag Key=Name; then
  echo "* Removed tag Name"
else
  echo "ERROR, cannot remove tag Name from instance '$id', is there a policy that allow action ec2:DeleteTags in the instance ROLE?"
  exit 4
fi

if aws ec2 create-tags --resources "$id" --tag Key=Name,Value="$HOSTNAME"; then
  echo "* Added tag Name=$HOSTNAME"
else
  echo "ERROR, cannot add tag Name to instance '$id', is there a policy that allow action ec2:CreateTags in the instance ROLE?"
  exit 5
fi

echo 
echo "==> Finished successfully!"