Dynamic DNS using Digital Ocean DNS

update_record.sh

#!/bin/bash
# Short script using the digital ocean API to update an A record with an IPV4 address
# from a specificed device. 
#
# I simply have cron run this every 30m. Ideally I wanted to have it run when openvpn
# had to reconnect and either (a) change device or (b) change IP.
#
# Pre-requisites:
# 1. DNS set up through Digital Ocean for this domain
# 2. API Token created with write access
# 3. Create a DNS record for this host ahead of time, you need the record ID to update
#    a record.

DO_TOKEN=__API__WRITE__ACCESS__
DOMAIN_NAME=dyn.example.com #FQDN you are putting your host under
HOST_NAME=drop-ovpn #Host name for the record
RECORD_ID=1111 #ID of the host record
DEV=$(ip tuntap show | cut -d: -f1) #Change to ETH0/ETH1 etc. This was for a VPN adapter
IF_IP=$(ip address show $DEV | awk ' FNR==3 {print substr($2,0, length($2) - 3) }')

# Run this to get record_ids for your DOMAIN_NAME from above.
#curl -X GET "https://api.digitalocean.com/v2/domains/$DOMAIN_NAME/records" -H "Authorization: Bearer $DO_TOKEN"

curl -X PUT "https://api.digitalocean.com/v2/domains/$DOMAIN_NAME/records/$RECORD_ID" \
        -H "Content-Type: application/json" \
        -H "Authorization: Bearer $DO_TOKEN" \
        -d "{\"type\":\"A\",\"name\":\"$HOST_NAME\",\"data\":\"$IF_IP\"}"
echo