My ISP provider allows an interface with their DNS via ddclient protocol. We will use the ddclient on the server to update DNS every time the external IP changes.

Install the ddclient

sudo apt-get install ddclient

At the installation questions choose

Other

Dynamic DNS server

www.ovh.com

Protocol

dyndns2

Username

scottworld.net-solaris

You can answer through the questions…. check the /etc/ddclient.conf file for settings below.

Edit the /etc/ddclient.conf

sudo nano /etc/ddclient.conf

daemon=600                  # check every 600 seconds
syslog=yes                  # log update msgs to syslog
mail=mark@scottworld.net                   # mail all msgs to root
mail-failure=mark@scottworld.net           # mail failed update msgs to root
pid=/var/run/ddclient.pid   # record PID in file.
cache=/tmp/ddclient.cache   # Cache file

### Select one of these options to determine your IP address

## via hardware interface (if you don't have a router/firewall)
#use=if, if=eth0

## via our CheckIP server
use=web, web=www.scottworld.net/ip.php, web-skip='IP Address'
#use=web, web=checkip.dynu.com/, web-skip='IP Address'


## from the status page for a linksys router/firewall
#use=linksys, fw=linksys, fw-login=admin, fw-password=admin

## from a FW status page
#fw-login=admin, fw-password=XXXXXX
#use=fw, fw=192.168.1.254/status.htm, fw-skip='IP Address'


## Enter your Ovh DynHost username and password here

login=XXXXXXXX        # your Ovh DynHost username
password=XXXXXXXX     # your Ovh DynHost password


## This section requires no changes unless you need to set a default proxy server
## or you need to bypass your proxy server (because it interferes with the updates)

protocol=dyndns2                    # default protocol
server=www.ovh.com           # default server
#server=members.dyndns.org:8245     # default server (bypassing proxies)
#proxy=fasthttp.sympatico.ca:80     # default proxy


## Default options for Dynamic/Static DNS Hosts

#mx=             # default MX host (leave undefined by default)
#backupmx=NO     # MX host is primary MX? (leave undefined by default)
#wildcard=YES     # add wildcard CNAME?

## Dynamic DNS hosts go here
solaris.scottworld.net

## Static DNS hosts go here
#static=yes, your-static-host.dyndns.org,another-static-host.dyndns.org

## Custom DNS hosts go here
#custom=yes, your-domain.top-level,your-other-domain.top-level

We then mount a file on the web “ip.php” (this returns your external ip address) This is pointed to in the ddclient config file via the entry use=web, web=www.scottworld.net/ip.php, web-skip='IP Address'

The WEB file contains this php / HTML to return the external IP remote address.

<?php
$ipaddress = "Current IP Address: ".$_SERVER['REMOTE_ADDR'];
echo $ipaddress;
?>