New comers to the Linux generally asks for what is the purpose and usage of the /etc/hosts
file. /etc
directory holds system and service related configuration. hosts
file is used to store host name or DNS to IP address resolution. It provides easy way to match a host or DNS name with an IP address.
List Current Host or DNS to IP Address Resolutions
We can easily read and print current content of the /etc/hosts
file. Its structure is very easy to read as we will examine it below.
$ cat /etc/hosts

Hostname
FQDN is structured naming of hosts in computer networks. You can read following tutorial to get more details about FQDN.
What is FQDN (Fully Qualified Domain Name) with Examples?
We can use FQDN is hosts
file but providing host and domain name like below. In this case we add host test
which is under lab.com
domain with IP address 192.168.1.100
192.168.1.100 test.lab.com
Alias
As a system administrator we generally prefer to use practical ways. If the host is in the same domain with us or domain is not important we can just provide the alias like below. In this example we will provide alias test
to the IP address 192.168.1.100
192.168.1.100 test
Alias with Hostname
hosts
file also provides the ability to use both single alias
or hostname. We will add them for the same IP address. Syntax is like below.
IPADDRESS HOSTNAME ALIAS
In this example the IP address is 192.168.1.100
alias is test
and hostname is test.lab.com
#IPADDRESS HOSTNAME ALIAS 192.168.1.100 test.lab.com test