How to install and configure inadyn on CentOS 6

Introduction

Inadyn is a command line utility for periodically checking and updating your ip address with DynDNS.

The guide will walk you through installing and configuring inadyn as a service on Centos 6.

All commands in this guide will either need to be run as the root user or with sudo.

Requirements

If you’re running CentOS x86_64 you’ll need to install the i686 version of glibc for inadyn to work.

yum install glibc.i686

Install Binary

First we need to download and install the binary. DynDNS makes the utility, along with the source code, available as a zip file which you can download from their website.

Let’s download and extract this zip file into /tmp.

cd /tmp
wget http://cdn.dyndns.com/inadyn.zip
unzip inadyn.zip

Next we’ll copy the binary into /usr/bin and make it executable.

cp inadyn/bin/linux/inadyn /usr/bin/inadyn
chmod 755 /usr/bin/inadyn

Create config file

When running inadyn you can specify your options on the command line but as we will be running it as a service we’re going to put all of our options in a config file.

Inadyn will check this config file automatically if you run it without options so we’ll open it for editing.

vi /etc/inadyn.conf

Enter the following options and update your username, password and alias.

# Basic configuration file for inadyn
#
# /etc/inadyn.conf
update_period_sec 600 # Check for a new IP every 600 seconds
username <username>
password <password>
dyndns_system dyndns@dyndns.org
alias <your dyndns domain>
background

As we’ve stored our password in plain text let’s ensure that only those who need to see it can.

chmod 640 /etc/inadyn.conf

Create init script

Next we’ll create an init script for inadyn so it can start automatically on boot.

vi /etc/init.d/inadyn

This is a modified version of the script provided by trendyserial here.

I’ve updated it to make it chkconfig friendly for CentOS and also added a status option so we can check if it is running. Copy it into your file.

#!/bin/bash
#
# inadyn				Startup script for the DynDNS update service
#
# chkconfig: 5 85 15
# description: inadyn updates DynDNS with the current ip address	\
#	             of the server.
# processname: inadyn
# config: /etc/inadyn.conf
# pidfile: /tmp/inadyn.pid
#
case "$1" in
  start)
    if [ -f /tmp/inadyn.pid ]; then
      PID=$(cat /tmp/inadyn.pid)
      kill -0 ${PID} &>/dev/null
      if [ $? = 0 ]; then
        echo "inadyn is already running."
      else
        /usr/bin/inadyn
        pidof inadyn > /tmp/inadyn.pid
        PID=$(cat /tmp/inadyn.pid)
        kill -0 ${PID} &>/dev/null
        if [ $? = 0 ]; then
          echo "inadyn started succesfully."
        else
          echo "Error starting inadyn"
        fi
      fi
    else
      /usr/bin/inadyn
      pidof inadyn > /tmp/inadyn.pid
      PID=$(cat /tmp/inadyn.pid)
      kill -0 ${PID} &>/dev/null
      if [ $? = 0 ]; then
        echo "inadyn started succesfully."
      else
        echo "Error starting inadyn"
      fi
    fi
  ;;

  stop)
    if [ -f /tmp/inadyn.pid ];then
      PID=$(cat /tmp/inadyn.pid)
      kill -0 ${PID} &>/dev/null
      if [ $? = 0 ]; then
        /bin/kill ${PID}
        kill -0 ${PID} &>/dev/null
        if [ $? = 1 ]; then
          echo "inadyn stopped succesfully."
        else
          echo "Error stopping inadyn"
        fi
      else
        echo "inadyn is already stopped."
      fi
    else
      echo "inadyn is already stopped."
    fi
  ;;

  status)
    PID=$(cat /tmp/inadyn.pid)
    if ps -p $PID > /dev/null
    then
      echo "inadyn is running"
    else
      echo "inadyn is not running"
    fi
  ;;

  reload|restart)
    $0 stop
    $0 start
  ;;

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

We also need to make the script executable so chkconfig can run it.

chmod +x /etc/init.d/inadyn

Add to chkconfig

We need to make chkconfig aware of the script and turn it on so that it starts on boot.

chkconfig --add inadyn
chkconfig inadyn on

We can check to make sure inadyn has been added to chkconfig

chkconfig --list inadyn
inadyn         	0:off	1:off	2:on	3:on	4:on	5:on	6:off

Start service

Then we need to start the service for the first time.

service inadyn start

You should get some output which looks like this

inadyn started succesfully.

If you want to see what inadyn is doing you can see its log messages in /var/log/messages.

If you check now you should see some messages similar to these

Jan  5 22:00:22 gateway INADYN[15973]: INADYN: Started 'INADYN version 1.96.2' - dynamic DNS updater.
Jan  5 22:00:22 gateway INADYN[15973]: I:INADYN: IP address for alias 'mydomain.dyndns.org' needs update to 'x.x.x.x'
Jan  5 22:00:23 gateway INADYN[15973]: I:INADYN: Alias 'mydomain.dyndns.org' to IP 'x.x.x.x' updated successful.

Uninstallation

To remove inadyn from your system for any reason simply run the following commands

service inadyn stop
chkconfig --del inadyn
rm /etc/init.d/inadyn /etc/inadyn.conf /usr/bin/inadyn