I've been reading the guides on linode about setting up a server to host websites. One concept that bothers me most is FQDN. From what I've read, FQDN is very important and it MUST be set. In my actual case, I've been running 2 linode servers for years, for one of them I just set it with my name shenkwen shenkwen

for the other I leave it as the default       ubuntu.members.linode.com       ubuntu

For these 2 servers, I've never encountered any problem regarding not properly setting FQDN. So I don't understand why setting a FQDN is important and when I am going to regret that I didn't set one properly.

Also I am reading this guide on github, it says

Hostnames are also important because they form part of a computer's Fully Qualified Domain Name (FQDN). Assigning a FQDN to a computer makes it reachable via the public Domain Name System (DNS), i.e. the Internet.

I am really confused by why the computer is reachable by just setting a FQDN. I mean I can set FQDN to anything, for example stackoverflow.com, but how can internet reach to my computer by this "FQDN"?

  • I don't understand why this question is getting so many downvotes, I clearly describe the question and show my approach to learning. Is asking a little help with understanding a basic concept too much? – shenkwen Aug 21 '18 at 14:40

What is more important than a FQDN is the server has a sense of self-identity and it can confirm it. So /etc/hostname should have a simple hostname in there (I have multiple linode machines, so I use node1, node2, etc). That same name should have a pointer to or in /etc/hosts

You'll need a real DNS-level FQDN if you want to use DNS to access your box, get SSL certs, etc. Good thing is linode GIVES you a FQDN - in the form of liNN-NNN.members.linode.com where the Ns are numbers (and may be more of them). You can see it in your control panel under "remote access" or contact the support folk.

If you start configuring services - mail, http/https, etc - then each service will have a config file (or files) and you can specify in that what hostname/FQDN to respond to. As long as DNS is pointing that hostname/FQDN to your IP, stuff will work.

Depending on what you do with your machine - for example, if you set up a mail server it MIGHT pull your hostname, etc. in to create its own config on initial install.

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