/etc/hosts: Explanation & Insights

Maps hostnames to IP addresses

The /etc/hosts file is a plain text file in Linux (and other operating systems) that maps hostnames to IP addresses. When a user tries to access a hostname, the operating system checks the hosts file first to see if there is an entry for that hostname. If there is, the operating system uses the corresponding IP address to establish a connection to the host. If there is no entry in the hosts file for the hostname, the operating system will use the Domain Name System (DNS) to resolve the hostname to an IP address.

It is a useful tool for system administrators and developers to test network configurations and resolve hostnames locally without the need to use a DNS server.

Here is an example of the contents of a hosts file:

127.0.0.1       localhost
192.168.1.100   myserver

In this example, the hostname localhost is mapped to the loopback IP address 127.0.0.1, and the hostname myserver is mapped to the IP address 192.168.1.100.

To add or modify entries in the hosts file, you can use a text editor such as vi or nano. You will need to have root privileges to edit the file, so you may need to use the sudo command.

For example, to add a new entry to the hosts file using nano, you would enter the following command:

sudo nano /etc/hosts

This will open the hosts file in the nano text editor. You can then add or modify entries as needed, and save the file when you are finished.

It is important to note that the hosts file is only used to resolve hostnames to IP addresses on the local system. It is not used to resolve hostnames for other systems on the network. To resolve hostnames for other systems, you will need to use a DNS server.