Register DNS and variables from TAGS of instance

register-from-tags.sh

#! /bin/bash

# Last update 2018-06-21 v0.2
# Author: Tom R. 
#
# wishtrip-register-from-tags.sh -  Register DNS and variables from TAGS of instance
#       1) get tags into env and then register DNS
#       2) create /etc/rnt.conf with value of RNT_ENV from "Env" tag
#       3) Set the hostname from tag "Hostname"
#       4) Set the DNS in route53 from  tags "Host" and "Env"
#
# e.g. assuming the following tags:
#   Hostname    - bastion
#   Env         - dev
#
#   Creates the DNS:
#       bastion.dev.ext.wishtrip.com
#       bastion.dev.int.wishtrip.com
#
# Dependancies:
#   requires AWS CLI
#   requires working outgoing network
#   Requires AWS permissions: ec2:read tags, dns create & update
#   requires sudo permission (with no passwd) to update hostname
#            and create /etc/rnt.conf
#
# Can install as regular script
#    # sudo install  -D register-from-tags.sh  /opt/wishtrip/register-from-tags.sh
#
# Should be installed as startup script if you want the RNT_ENV set early
#       # update-rc.d  register-from-tags start  01 3 .
#

# debug
exec 1>/tmp/register-from-tags.log
exec 2>>/tmp/register-from-tags.log
set -x

logger -t wishtrip "Starting $0"

#
# Name - get-ec2-tag    <Tag_Name>
#
#  Returns - value of <Tag_Name>
#           - null if tag does not exist or any other error

get-ec2-tag()
{
    TAG_NAME=$1
    aws ec2 describe-tags --debug --filters "Name=resource-id,Values=$INSTANCE_ID" "Name=key,Values=${TAG_NAME}" --region=$EC2_REGION --output=text | cut -f5
}


# add /usr/local/bin to include AWS tools (when called from init script)
PATH=$PATH:/usr/local/bin

# If AWS not installed, abort
command -v aws >/dev/null 2>&1 || { echo >&2 "$0: aws CLI not installed. Aborting."; logger -t wishtrip "$0: aws CLI not installed. Aborting." exit 1; }


INSTANCE_ID=$(curl -s http://169.254.169.254/latest/meta-data/instance-id)
EC2_AVAIL_ZONE=$(curl -s http://169.254.169.254/latest/meta-data/placement/availability-zone)
EC2_REGION=$(echo $EC2_AVAIL_ZONE | sed 's/[a-z]$//')
#EC2_REGION=$(curl -s http://169.254.169.254/latest/dynamic/instance-identity/document|grep region|cut -d\" -f4)

[[ -z $EC2_REGION ]] && (echo  >&2 "Variable is unset";exit 1)

# make sure network and DNS are up before continuing
# test access to AWS EC2 endpoint
until nc -zw1 ec2.${EC2_REGION}.amazonaws.com  443; do echo "waiting for network"; sleep 1; done


# set RNT_ENV from Env tag
RNT_ENV=$(get-ec2-tag "Env")

if [[ -z $RNT_ENV ]]
then
    echo Error: Could not get tag Env
    exit 1
fi

# create /etc/rnt.conf
# put the "export" on a seperate line so the file is compatible with systemd EnvironmentFile=
sudo bash -c "echo -e RNT_ENV=$RNT_ENV \\\\nexport RNT_ENV > /etc/rnt.conf"

Host=$(get-ec2-tag "Hostname")

if [[ -z $Host ]]
then
    echo Error: Could not get tag  Host
    exit 1
fi

sudo hostname $Host.$RNT_ENV
sudo bash -c "echo $Host.$RNT_ENV > /etc/hostname"
sed -i 's/127.0.0.1.*/127.0.0.1\t'"localhost $Host.$RNT_ENV"'/g' /etc/hosts


#
# Register DNS
#

# Get the local and public IP Address that is assigned to the instance
#LOCAL_IPV4=$(ec2metadata  --local-ipv4)
#PUBLIC_IPV4=$(ec2metadata --public-ipv4)

LOCAL_IPV4=$(curl -s http://instance-data/latest/meta-data/local-ipv4)
PUBLIC_IPV4=$(curl -s http://instance-data/latest/meta-data/public-ipv4)

Domain=wishtrip.com
TTL=60

logger -t wishtrip "$0: About to add DNS: $Host.$RNT_ENV.int.$Domain A $LOCAL_IPV4"

# replace cli53 with aws cli
# Create a new or update the A-Records on Route53 with public and private IP address
#cli53 rrcreate --replace "$Domain" "$Host.$RNT_ENV.int $TTL A $LOCAL_IPV4"
#cli53 rrcreate --replace "$Domain" "$Host.$RNT_ENV.ext $TTL A $PUBLIC_IPV4"


domain-name2id()
{
# Description - converd DNS domain name to AWS Zone ID
# - input 1 - DNS name to convert
# output Zone ID

    [[ -z $1 ]] && (echo "$0 missing arg";exit 1)

    Domain=$1
    aws route53 list-hosted-zones  --output text |grep wishtrip.com|cut -f3|cut -d/ -f3
}

Zone=$(domain-name2id $Domain)


# Json template
Json_tpl='
{
  "Comment": "Update the A record set",
  "Changes": [
    {
      "Action": "UPSERT",
      "ResourceRecordSet": {
        "Name": "_NAME_._DOMAIN_",
        "Type": "A",
        "TTL": _TTL_,
        "ResourceRecords": [
          {
            "Value": "_IP_"
          }
        ]
      }
    }
  ]
}
'

# Update json template
TTL=60
Json=$Json_tpl
Json="${Json/_DOMAIN_/$Domain}"
Json="${Json/_TTL_/$TTL}"


# Update json template
NAME=$Host.$RNT_ENV.int
IP=$LOCAL_IPV4
Json="${Json/_NAME_/$NAME}"
Json="${Json/_IP_/$IP}"

aws route53 change-resource-record-sets --hosted-zone-id $Zone --change-batch "$Json"

# Register external IP if it exists
if [[ $PUBLIC_IPV4 != *xml* ]]
then


# Update json template
Json=$Json_tpl
Json="${Json/_DOMAIN_/$Domain}"
Json="${Json/_TTL_/$TTL}"

NAME=$Host.$RNT_ENV.ext
IP=$PUBLIC_IPV4
Json="${Json/_NAME_/$NAME}"
Json="${Json/_IP_/$IP}"

logger -t wishtrip "$0: About to add EXT DNS: $NAME$Domain A $LOCAL_IPV4"

aws route53 change-resource-record-sets --hosted-zone-id $Zone --change-batch "$Json"
fi

logger -t wishtrip "Finished $0"

TBD

• resolve.conf
  Also update /etc/resolve.conf by updated the "search to look at the local subdomain, e.g.
  search dev1.int.wishtrip.com