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Understanding Linux name resolution
In 
Chapter 11
, 
Setting Up Network Services
, we'll have a discussion on setting up a DNS 
server for local name resolution for your network. But before we get to that, it's also 
important to understand how Linux resolves names in the first place. Most of you 
are probably aware of the concept of a 
Domain Name System
 (
DNS
), which matches 
human-understandable domain names to IP addresses. This makes browsing your 
network (as well as the internet) much easier. However, a DNS isn't always 
the first 
thing that your Linux server will use when resolving names.
For more information on the order in which Ubuntu Server checks resources to 
resolve names, feel free to take a look at the 
/etc/nsswitch.conf
 file. There's a line in 
this file that begins with the word 
hosts
. Here is the output of the relevant line from 
the file on my server:
hosts:          files dns 
In this case, the server is configured to first check local files, and then the DNS 
if the request isn't found. This is the default order, and I see little reason to make 
any changes here (but you certainly can). Specifically, the file the server will check 
is 
/etc/hosts
. If it doesn't find what it needs there, it will move on to the DNS 
(basically, it will check the DNS server we configured earlier with Netplan, or the 
default server provided by DHCP).
There are many other lines in the 
nsswitch.conf
 file, but I won't 
discuss them here as they are out of scope of the topic of this 
section.

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Chapter 10