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Dynamic DNS on Raspberry Pi

03 Jun 2016

How are web requests processed?

When a user visits a web site, they use the site’s domain name to address the site. Their browser then sends a request to a DNS server to translate the domain name into an IP address. Once the browser has the site’s IP address, it sends a request to the server.

There are two problems with this:

  • 1. the external IP address of your home network can change at any time, and
  • 2. your Pi is behind a firewall and can’t be accessed directly from the internet.

Dynamic DNS

The first problem can be solved by using a dynamic DNS service. These services act as DNS servers that update automactically if your IP address changes. There are numerous dynamic DNS services available. Most of them provide a free service where you can choose a subdomain name.

You need to install a small piece of software on your Pi. This software is supplied by your dynamic DNS provider, and it monitors the external address of your router. If that address changes, the software sends a message to the dynamic DNS server to update its records.

Port forwarding

When a user on the internet wants to see your web site, their browser can get the IP address of your home network from your dynamic DNS service. But requests still need to find a way through your router’s firewall.

By default web servers listen for connections on port 80. When a user’s request to see a page on your site reaches your router, the router must forward that request to your Pi’s IP address. You don’t want to forward all incoming traffic to your Pi, just the traffic for the web server which is on port 80. Most routers allow you to set up port forwarding so that any traffic on port 80 will be sent to your Pi.

To create a domain name that always points to your home ip:

Goto www.noip.com > create an account

  1. Sign in to your noip account > goto Add Host> create your host name with one of the offered domain names (mpmendespt.ddns.net)
  2. Keep the Host type as DNS Host A ( If your ISP blocks Port 80 for example, and you’re trying to run a webserver or other service on port 80, then you can choose Port 80 Redirect (at that point you’ll be asked to specify the port to use for the redirection)
  3. In the field marked IP Address: you should already see your current IP address.
  4. The next two options aren’t used for a basic account setup so leave them as they are.
  5. click the “Add Host” button at the bottom of the page to save it.

Install No-IP’s Dynamic Update Client

Create a directory for the client software:

mkdir /home/pi/noip

Download the client software:

wget https://www.noip.com/client/linux/noip-duc-linux.tar.gz

Extract the archive:

tar zxvf noip-duc-linux.tar.gz

Compile and install:

sudo make

sudo make install

After typing “sudo make install” you will be prompted to login with your No-IP account username and password.

After logging into the DUC answer the questions to proceed. When asked how often you want the update to happen you must choose 5 or more. The interval is listed in minutes, if you choose 5 the update interval will be 5 minutes. If you choose 30 the interval will be 30 minutes.

Please enter an update interval:[30] 10

Do you wish to run something at successful update?[N] (y/N) \^M

New configuration file ‘/tmp/no-ip2.conf’ created.

mv /tmp/no-ip2.conf /usr/local/etc/no-ip2.conf

The Dynamic Update client is started by running:

sudo /usr/local/bin/noip2

To confirm that the service is working properly you can run the following command:

sudo noip2 -S

To start the client when the system reboots.

We write a start up script:

sudo nano /etc/init.d/noip2

with the following lines:

#! /bin/sh
# /etc/init.d/noip2

# Supplied by no-ip.com
# Modified for Debian GNU/Linux by Eivind L. Rygge <eivind@rygge.org>
# Updated by David Courtney to not use pidfile 130130 for Debian 6.
# Updated again by David Courtney to "LSBize" the script for Debian 7.

### BEGIN INIT INFO
# Provides:     noip2
# Required-Start: networking
# Required-Stop:
# Should-Start:
# Should-Stop:
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Start noip2 at boot time
# Description: Start noip2 at boot time
### END INIT INFO

# . /etc/rc.d/init.d/functions  # uncomment/modify for your killproc

DAEMON=/usr/local/bin/noip2
NAME=noip2

test -x $DAEMON || exit 0

case "$1" in
    start)
    echo -n "Starting dynamic address update: "
    start-stop-daemon --start --exec $DAEMON
    echo "noip2."
    ;;
    stop)
    echo -n "Shutting down dynamic address update:"
    start-stop-daemon --stop --oknodo --retry 30 --exec $DAEMON
    echo "noip2."
    ;;

    restart)
    echo -n "Restarting dynamic address update: "
    start-stop-daemon --stop --oknodo --retry 30 --exec $DAEMON
    start-stop-daemon --start --exec $DAEMON
    echo "noip2."
    ;;

    *)
    echo "Usage: $0 {start|stop|restart}"
    exit 1
esac
exit 0

Then give it executable permissions and update the rc.d scripts:

sudo chmod +x /etc/init.d/noip2
sudo update-rc.d noip2 defaults

Now it automatically update it’s ip on boot.

References

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