AWS EC2: set a node's hostname to it's tagged name

ec2_set_hostname_from_tag.sh

#!/bin/bash
set -ex

# Sanity check
hostname="$(hostname --fqdn)"
if [[ "$hostname" != ip-*.internal ]]; then
    echo hostname already updated
    exit 0
fi

# Install requirements
apt update
apt install -y --no-install-recommends jq python3-pip python3-wheel
pip3 install awscli

# Configure awscli
export AWS_DEFAULT_REGION="$(hostname --fqdn | cut -d. -f2)"

# Get tagged hostname
current_hostname="$(hostname --fqdn)"
instanceid="$(aws ec2 describe-instances --filter Name=private-dns-name,Values="$current_hostname" | jq -r .Reservations[0].Instances[0].InstanceId)"
new_hostname="$(aws ec2 describe-tags --filters Name=resource-id,Values="$instanceid" | jq -r '.Tags[] | select(.Key == "Name") | .Value')"
if [ -z "$new_hostname" ]; then
    echo new hostname not found
    exit 1
fi

# Update hostname
hostname "$new_hostname"
echo "$new_hostname" >/etc/hostname