Configure a static IP on Ubuntu Server 14.04

20151229113855At home I use Ubuntu Server 14.04 and have never had to set  static IP as I would configure a static IP/mac address mapping in my router’s DHCP settings so it would always get the same address . That was until last week when I had to look up the exact steps on Google. Needless to say,  the process is straight-forward, here are the steps to configure a static IP on Ubuntu Server 14.04:

The Steps

1. The first thing to mention is that the interface config file in Ubuntu looks a little weird if you are used to working with only RHEL/CentOS. By default Ubuntu Server enables DHCP on a network interface. To configure the interface you have to edit the /etc/network/interfaces file. Below I am opening it with vi editor:

admin@web01:~$ sudo vi /etc/network/interfaces file

You will see something similar to the below:

This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet dhcp

2. As you can see from the above eth0 is set to use DHCP and not a static IP. I want to set a static IP with the following info:

IP address10.10.10.50
Subnet Mask255.255.255.0
Default Gateway10.10.10.1
DNS Server 110.10.10.1
DNS Server 28.8.8.8

To achieve this, change iface eth0 inet dhcp to iface eth0 inet static. Then add the network parameters per the below:

This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet static
address 10.10.10.50
netmask 255.255.255.0
gateway 10.10.10.1
dns-nameservers 10.10.10.1 8.8.8.8

Save the changes and exit.

3. The next step is to update the /etc/hosts file by opening it with vi or any other editor of your choice:

admin@web01:~$ sudo vi /etc/hosts

You should see the lines below:

127.0.0.1   localhost
127.0.1.1   web01

Add a new line under the existing lines containing the static IP and relevant hostname(s):

127.0.0.1   localhost
127.0.1.1   web01
10.10.10.50     web01

Save the changes and exit the file.

4. To commit the changes made in the steps above you can either reboot the server or restart the network services. Restart the network services by running:

admin@web01:~$ sudo ifdown eth0 & sudo ifup eth0

Please note that in previous version of Ubuntu server you could run service networking restart to restart services. This no longer works in Ubuntu Server 14.04. You need to shut down the interface and then bring it back up per step 4 above.

After restarting the network services the operating system and all applications will recognise and use the new IP.

Please also note that restarting the network services will force an update to the /etc/resolve.conf file. It will automatically add the DNS servers we configured in step 2 above to the file. We can confirm this by reading the file:

admin@web01:~$ cat /etc/resolv.conf

The output is:

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 10.10.10.1
nameserver 8.8.8.8

That’s it! Your Ubuntu Server is now running using a static IP.

References:
Linux Basics – Set A Static IP On Ubuntu
Official Ubuntu Documentation > Network Configuration > Interfaces

Change hostname on Ubuntu Server 14.04

20151229113855Sometimes I forget some of the steps to changing the hostname on Ubtuntu as they vary slightly to other Linux distros such as RHEL or CentOS. The process is just as simple but there is a slight difference in that we need to amend the hostname file. So without further ado, here are the steps to change the hostname on Ubunutu Server 14.04:

The Steps

1. The first step is to run the hostname command followed by the new server name and hit Enter:

admin@web01:~$ sudo hostname web02

2. As you can see from the above the current hostname was web01, I changed it to web02. Running the hostname command on it’s own will show you the current and new hostname of web02:

admin@web01:~$ hostname
web02

The hostname has now been changed, however this change is not permanent. In other words if you reboot the server the changes will not survive, the hostname will revert back to its previous name. To make the hostname change permanent continue to step 3 below.

3. The next step is to update the /etc/sysconfig/network file by opening it with vi or any other editor of your choice:

admin@web01:~$ sudo vi /etc/hostname

4. Within the file you will see your old hostname, in my case web01:

web01

Simply change the hostname to the new name, in my case it is web02:

web02

Exit and save the changes to the file.

5. We have one final file to update, which is /etc/hosts. Edit it vi:

admin@web01:~$ sudo vi /etc/hosts

You should see the lines below, the bottom line showing your old hostname, in my case web01:

127.0.0.1   localhost
127.0.1.1   web01

Once again, change it to reflect the new desired hostname, in my case web02:

127.0.0.1   localhost
127.0.1.1   web02

Exit and save the changes to the file. The changes so far should be enough to ensure your system recognises the new hostname. I like to restart networking services to ensure that the new changes take effect, to do this proceed to step 6 below.

6. To commit the changes made in the network, hostname and hosts files above in steps 4 & 5 respectively you can either reboot the server or restart the network services. Restart the network services by running:

admin@web01:~$ sudo ifdown eth0 && sudo ifup eth0

Please note that in previous version of Ubuntu server you could run service networking restart to restart services. This no longer works in Ubuntu Server 14.04. You need to shut down the interface and then bring it back up per step 6 above.

After restarting the network services the operating system and all applications will use the new hostname.

References:
How to successfully restart a network without reboot over SSH?
How do I change the hostname without a restart?