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Dynamic Host Configuration Protocol, shortly known as DHCP, is very useful tool when it comes to networking with multiple computers in the network. It is a must have tool for an office network infrastructure. Of course, you can live without it, but it makes sysadmin’s life much more easier and let’s users just plug in their network cables and they are in the network. You can read more about DHCP here.

Ok, so let’s look at how we install DHCP in Ubuntu 6.06.1 LTS (Dapper Drake). I assume you did a clean install of Ubuntu Linux server edition or at least have a working Ubuntu running in your box.

So steps:

1. You should set your IP settings to static. You can do it by editing file/etc/network/interfaces config file. For the primary interface, usually it’s eth0, you will see following lines:

auto eth0
iface eth0 inet dhcp

You may set different IP settings here, in my case I change those lines to:

auto eth0
iface eth0 inet static
address 192.168.1.100
netmask 255.255.255.0
network 192.168.1.0
broadcast 192.168.1.255
gateway 192.168.1.1

2. Set your DNS Servers editing /etc/resolv.conf file.

3. sudo /etc/init.d/networking restart

4. sudo apt-get update

5. sudo apt-get install dhcp3-server

6. sudo vim /etc/defaults/dhcp3-server
Add your interface name in the settings file. ( INTERFACES=”eth0″ )
We know that right after installing dhcp3-server packages it tries to start it but fails. So now that we changed default interface it will listen to we try again to start the server by typing:

7. sudo /etc/init.d/dhcp3-server start
8. All the logs from dhcp server is sent to syslog, we check it:

arstan@ubuntu:~$ sudo tail -f /var/log/syslog
Jul  6 13:03:24 ubuntu dhcpd: Wrote 0 leases to leases file.
Jul  6 13:03:24 ubuntu dhcpd:
Jul  6 13:03:24 ubuntu dhcpd: No subnet declaration for eth0 (192.168.1.100).
Jul  6 13:03:24 ubuntu dhcpd: ** Ignoring requests on eth0.  If this is not what
Jul  6 13:03:24 ubuntu dhcpd:    you want, please write a subnet declaration
Jul  6 13:03:24 ubuntu dhcpd:    in your dhcpd.conf file for the network segment
Jul  6 13:03:24 ubuntu dhcpd:    to which interface eth0 is attached. **

So why is it still not starting up? After doing some digging in /etc/init.d/dhcp3-server start script I found that it has the following lines:

# Allow ltsp to override
if [ -f /etc/ltsp/dhcpd.conf ]; then
CONFIG_FILE=/etc/ltsp/dhcpd.conf
break
fi

Since we don’t need ltsp configs in this case, let’s just comment them out. You can do so by adding # at the beginning of each line.

Let’s restart the server by typing:

sudo /etc/init.d/dhcp3-server start

That’s all about it! You know have DHCP server configured in Ubuntu Linux.

Have fun!

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