Should /etc/hosts Contain Domain Name or FQDN?

dnshostsinternetnetworking

If I want to add an entry to /etc/hosts to resolve all traffic for example.com to 1.2.3.4, do I need to add

1.2.3.4    example.com
1.2.3.4    www.example.com
1.2.3.4    smtp.example.com
1.2.3.4    pop.example.com
...

Or will just adding

1.2.3.4    example.com

suffice?

Best Answer

You will need to specify each and every subdomain. If that is not what you want, you should look into installing a real DNS server (e.g. bind9).

This is rather easy to check by first adding just example.com to /etc/hosts and then do 

ping -c 2 example.com
ping -c 2 www.example.com

The first will succeed with the provided IP address. The second will go to 93.184.216.119 (the IP address in the internet for www.example.com)

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