A simple script to start an AWS EC2 instance and update an associated R53 DNS record. The policy files should setup minimum permissions to allow these actions.

aws-manage.sh

#!/bin/bash
# Dependencies: awscli - see https://aws.amazon.com/cli/
# Some of this is pilfered from
# https://github.com/awslabs/aws-codedeploy-samples
#
# How to use:
# ./aws-manage.sh <instance id> <dns-record> <dns-type> <up|down>
#
# For example:
# ./aws-manage.sh i-7337 xntrik.wtf A up
#


DEBUG=true          #print messages
AWS_CLI="aws"       #in case you need more CLI options? 
WAITER_ATTEMPTS=24  #how many times the wait_for_state tries
WAITER_INTERVAL=5   #and how long we wait each try
TTL=300             #DNS TTL

msg() {
    local message=$1
    $DEBUG && echo $message 1>&2
}

error_exit() {
    local message=$1
    echo "[FATAL] $message" 1>&2
    exit 1
}

instance_status() {
    local instance_id=$1

    local state=$($AWS_CLI ec2 describe-instances --instance-ids $instance_id \
        --query 'Reservations[0].Instances[0].State.Name' \
        --output text)
    if [ $? != 0 ]; then
        return 1
    else
        echo $state
        return 0
    fi
}

wait_for_state() {
    local service=$1
    local instance_id=$2
    local state_name=$3

    local instance_state_cmd
    if [ "$service" == "ec2" ]; then
        instance_state_cmd="instance_status $instance_id"
    else
        msg "Cannot wait for instance state; unkonwn service type, '$service'"
        return 1
    fi

    msg "Checking $WAITER_ATTEMPTS times, every $WAITER_INTERVAL seconds for instance $instance_id to be in $state_name"

    local instance_state=$($instance_state_cmd)
    if [ $? != 0 ]; then
        msg "Couldn't get initial state"
        return 1
    fi

    local count=1

    while [ "$instance_state" != "$state_name" ]; do
        if [ $count -ge $WAITER_ATTEMPTS ]; then
            local timeout=$(($WAITER_ATTEMPTS * $WAITER_INTERVAL))
            msg "Instance failed to reach state, $state_name within $timeout"
            return 1
        fi

        sleep $WAITER_INTERVAL

        instance_state=$($instance_state_cmd)
        count=$(($count + 1))
        msg "Instance is currently in state: $instance_state"
    done

    return 0
}

stop_instance() {
    local instance_id=$1

    msg "Checking instance state"

    local instance_state=$(instance_status $instance_id)
    if [ $? != 0 ]; then
        msg "Unable to get instance state"
        return 1
    fi

    if [ "$instance_state" != "running" ]; then
        msg "Instance is not running, therefore we can't stop"
        return 1
    fi

    msg "Instance is ready to stop.."

    $AWS_CLI ec2 stop-instances --instance-ids $instance_id

    if [ $? != 0 ]; then
        msg "Failed to stop instance"
        return 1
    fi

    msg "Waiting for instance to be stopped"

    wait_for_state "ec2" $instance_id "stopped"

    if [ $? != 0 ]; then
        msg "Instance didn't appear to stop in time"
        return 1
    fi

}

start_instance() {
    local instance_id=$1

    msg "Checking instance state"

    local instance_state=$(instance_status $instance_id)
    if [ $? != 0 ]; then
        msg "Unable to get instance state"
        return 1
    fi

    if [ "$instance_state" != "stopped" ]; then
        msg "Instance is not stopped, therefore we can't start"
        return 1
    fi

    msg "Instance is ready to start.."

    $AWS_CLI ec2 start-instances --instance-ids $instance_id

    if [ $? != 0 ]; then
        msg "Failed to start instance"
        return 1
    fi

    msg "Waiting for instance to be started"

    wait_for_state "ec2" $instance_id "running"

    if [ $? != 0 ]; then
        msg "Instance didn't appear to start in time"
        return 1
    fi

}

get_ipaddress() {
    local instance_id=$1

    local state=$($AWS_CLI ec2 describe-instances --instance-ids $instance_id \
        --query 'Reservations[0].Instances[0].PublicIpAddress' \
        --output text)
    if [ $? != 0 ]; then
        return 1
    else
        echo $state
        return 0
    fi
}

fetch_hosted_zone() {
    local dnsname=$1

    if [ "${dnsname: -1}" != "." ]; then
        dnsname="${dnsname}."
    fi

    zones=$($AWS_CLI route53 list-hosted-zones --output text \
            --query "HostedZones[*].[Id,Name]")

    while IFS= read -r line; do
        local testdnsname=$(echo $line|cut -f 2 -d " ")
        if [ "$testdnsname" == "$dnsname" ]; then
            local value=$(echo $line|cut -f 1 -d " ")
            value=$(echo $value|cut -f 3 -d "/")
            echo $value
            return 0
        fi
    done <<< "$zones"

    echo "No $2 DNS Name Found"
    return 1
}

fetch_dns_record() {
    local hostedzone=$1
    local recordtype=$2

    records=$($AWS_CLI route53 list-resource-record-sets --hosted-zone-id $1 \
        --query "ResourceRecordSets[*].[Type,ResourceRecords[0].Value]" \
        --output text)

    while IFS= read -r line; do
        local testrecordtype=$(echo $line|cut -f 1 -d " ")
        if [ "$testrecordtype" == "$recordtype" ]; then
            local value=$(echo $line|cut -f 2 -d " ")
            echo $value
            return 0
        fi
    done <<< "$records"

    echo "No $2 Record Found"
    return 1
}

update_ipaddress() {
    local ip=$1
    local action=$2
    local name=$3
    local recordtype=$4
    local comment=$5
    local hostedzone=$6

    local temp_file=$(mktemp)

    cat >${temp_file} << EOL
{
    "Comment": "${comment}",
    "Changes": [
        {
            "Action": "${action}",
            "ResourceRecordSet": {
                "Name": "${name}",
                "Type": "${recordtype}",
                "TTL": ${TTL},
                "ResourceRecords": [
                    {
                        "Value": "${ip}"
                    }
                ]
            }
        }
    ]
}
EOL

    $AWS_CLI route53 change-resource-record-sets --hosted-zone-id $hostedzone \
        --change-batch file://$temp_file

    rm ${temp_file}

    return 0
}

if [ $# -ne 4 ]; then
    error_exit "Params: instance-id dns-record dns-type <up|down>"
fi

INSTANCE_ID=$1
DNSNAME=$2
RECORDTYPE=$3
ACTION=$4

if [ $ACTION == "up" ]; then

    msg "Starting instance and waiting for it to be in running state" 
    
    instance_started=$(start_instance $INSTANCE_ID)
    
    if [ $? != 0 ]; then
        error_exit "We couldn't start the instance properly, so we stopped"
    fi
    
    msg "Updating the A record"

    hz=$(fetch_hosted_zone $DNSNAME)
    if [ $? != 0 ]; then
        error_exit "We couldn't get the hosted zone for: $DNSNAME"
    fi
    
    ip=$(get_ipaddress $INSTANCE_ID)
    if [ $? != 0 ]; then
        error_exit "We couldn't get the IP address of our instance: $ip"
    fi

    msg "Instance has the IP: $ip"
    
    updated_ip=$(update_ipaddress $ip "UPSERT" $DNSNAME $RECORDTYPE \
        "This is a comment" $hz)
    
    fetch_a=$(fetch_dns_record $hz $RECORDTYPE)
    if [ $? != 0 ]; then
        error_exit "We didn't update the $RECORDTYPE record properly: $fetch_a"
    fi
    
    msg "The $RECORDTYPE record for $DNSNAME is now: $fetch_a"

elif [ $ACTION == "down" ]; then

    msg "Stopping instance"

    ip=$(get_ipaddress $INSTANCE_ID)
    if [ $? != 0 ]; then
        error_exit "We couldn't get the IP address of our instance: $ip"
    fi

    instance_stopped=$(stop_instance $INSTANCE_ID)

    if [ $? != 0 ]; then
        error_exit "We couldn't stop the instance properly, so we quit.."
    fi

    msg "Removing the $RECORDTYPE record ($ip) from $DNSNAME"

    hz=$(fetch_hosted_zone $DNSNAME)
    if [ $? != 0 ]; then
        error_exit "We couldn't get the hosted zone for: $DNSNAME"
    fi

    removed_ip=$(update_ipaddress $ip "DELETE" $DNSNAME $RECORDTYPE \
        "Delete" $hz)

fi

ec2-iam-example-policy.json

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": "ec2:DescribeInstances",
            "Resource": "*"
        },
        {
            "Effect": "Allow",
            "Action": [
                "ec2:StopInstances",
                "ec2:StartInstances"
            ],
            "Resource": [
                "arn:aws:ec2:<region>:<account id>:instance/<instance id>"
            ]
        }
    ]
}

r53-iam-example-policy.json

{
    "Version": "2012-10-17",
   "Statement":[
      {
         "Action":[
            "route53:ChangeResourceRecordSets",
            "route53:GetHostedZone",
            "route53:ListResourceRecordSets"
         ],
         "Effect":"Allow",
         "Resource":[
            "arn:aws:route53:::hostedzone/<hosted zone id>"
         ]
      },
      {
         "Action":[
            "route53:ListHostedZones"
         ],
         "Effect":"Allow",
         "Resource":[
            "*"
         ]
      }
   ]
}