Here we look at changing the hostname and resolving the fully qualified domain name.
First open up the network script in a text editor
$ sudo /etc/sysconfig/network
Change the hostname value to your preferred name and then save and exit the file, if you want to rename the server to centosbox it will appear as
Avoid capitals and irregular characters when naming the host, use only apha-numeric characters under 63 characters in length.
Now confirm the settings for the server in order to complete the Fully Qualified Domain Name or FQDN. An FQDM consists of a hostname and the DNS-based domain name, so in order to do this we will need to open and edit the hosts file
$ sudo vi /etc/hosts
Now confirm the correct order and set the correct values with the intention of making the file look similar to the following.
Replace the values of the second line with something more appropriate, so if the server is called centosbox with an IP address of 192.168.0.100 and a domain name of centosbox.com then the final file will look like below.
If the server is on a local network, it is advisable to use a non-Internet based address. For example, you could use .local or .lan or .home.
By using these references you will avoid any confusion with the typical .com, .co.uk or .net domain names.
When done, save the file and reboot the server to allow the changes to take effect immediately.
Om rebooting, you can now check your new hostname by typing the following command and waiting for the response
To confirm the hostname type the following command and wait for the response
$ hostname -f
Or, as an alternative to the preceding method, to confirm the Fully Qualified Domain Name (FQDN), you can type the following command and wait for the response
$ hostname -fqdn
So, by changing the values in the two system configuration files /etc/sysconfig/network and /etc/hosts and rebooting the server we can easily change the hostname.
The hosts file is used by Centos to map hostnames to IP addresses and is often found to be incorrect on a new, un-configured or recently installed server. For this reason we first reorganise the references shown in order to support both the relevent IPv4 and IPv6 values as well as the hostname and domain name reference. So we rewrite the file to reflect the newly assigned values.
So to conclude we can say that we have not only renamed the server, but we have also dispelled the myths associated with hostnames as opposed to hostnames.
A server is not only known by the use of the shorter single word base name, it also consists of the three values separated with a period. The domain name remains distinct from the hostname because it is determined by the resolver system, and it is only by putting them both together that the server will give the Fully Qualified Domain Name or FQDN of the system.