How to Edit the Hosts File in Linux
What is the Hosts File?
The hosts file is a simple text file that allows you to map hostnames to IP addresses directly on your computer. It acts as a local DNS (Domain Name System) resolver, giving you control over how domain names are translated to IP addresses.
Key Purposes of the Hosts File
- Block Websites: Redirect unwanted domains to localhost (127.0.0.1)
- Override DNS Resolutions: Specify custom IP mappings
- Local Development and Website Migrations: Point domain names to local development servers. It can also be used to temporarily point the website to be migrated to the new server IP pre-migration before making the changes go live
- Improve Security: Block ads or malicious websites
Editing the Hosts File
Editing the hosts File in Linux is simple. It is located in /etc and can be directly opened through the Terminal. So use nano or vi or any of your favorite text editors. This example uses nano.
Important: Before changing the hosts file, as with most system related tasks, it is better to first backup the original. You can do that with the cp command:
sudo cp /etc/hosts /etc/hosts.bak
This will copy the contents of the original hosts file into a new file named hosts.bak (backup). Next, edit the original file using nano.
sudo nano /etc/hosts
The hosts file follows this format:
IP_ADDRESS hostname [optional_aliases]
So, first add the IP address followed by the hostname or domain to which it would point to.
Then save and exit. (In nano: Press Ctrl+O,� then Enter and for vi it would be :wq).
You can verify these host file changes by pinging the domain or opening it in the browser. It should be served over the added IP address from the hosts file.�
To roll back the changes, add a # in front of the entries in the file.
Important Considerations
- Changes take effect immediately
- Requires root/sudo privileges
- Modifications can impact system networking
- Be careful when editing to avoid breaking system resolving
Best Practices
- Always backup the original hosts file
- Use comments to explain your modifications
- Only make changes you fully understand
All done.
