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- In this video we'll
talk about host names.

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So how do you manage them?

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Well, first let's talk
about resolving host names.

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DNS is commonly used
for host name resolving.

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It's a worldwide standard and it's

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like you use all the times.

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But there is also etc host.

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Etc host is used to maintain local list

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of host names and matching IP addresses.

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Now the interesting question is,

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how does etc host relate to DNS?

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Well, the order for
host name resolution is

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in /etc/nsswitch.conf.

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So you, need to check out /etc/nsswitch.

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It's a name service switch

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and it is used to define the order

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in which host name
resolution should happen.

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And the line that you see
here might be what you find

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in it. Depends on your distribution.

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Now the important part is
that hosts defines the order

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and as long as files comes before DNS,

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then etc host is always going to win,

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and can be used to
override if you want to.

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/Etc/resolv.conf is the old standard

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for configuring DNS name servers.

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And on network manager
systems the file can be

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written directly, or it is
managed by network manager.

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And on systemd-networkd systems,

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a different approach is used.

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Here the file is managed
with systemd-resolved.

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And etc resolved is a symbolic link to

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/run/systemd/resolve/stub-resolv.conf

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for automatically managing it.

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Let's check out how the simulation works

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between etc hosts and DNS.

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So here we are on the
center s machine and let me

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use ping.google.com. And there we go,

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We are getting an answer from

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142.250.69.238.

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Now if I would use etc
hosts. And in etc host,

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I am setting 192.168.29.2

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and I call it google.com.

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And then we repeat ping.google.com.

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There we can see that
google.com is now 192.168.29.2.

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Which is obviously not the
real Google, but this is just

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showing that etc host is always winning

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from the DNS configuration.

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And that is because of /etc/nsswitch.conf

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in which we can find this
host's line. Let's look it up.

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And in this host's line we
have files DNS myhostname.

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I'm going to comment it out.

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I like commenting it out if
I'm playing with configuration

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files so that it's easy to
get back to the previous

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configuration. And now
I'm setting to DNS files.

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(keyboard clicking)

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And what is going to happen now,

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if we ping google.com, there you go.

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The internet is winning.

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So everything because
of /etc/nsswitch.conf.

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Before continuing, I
do advise you to revert

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to the original situation.

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(keyboard clicking)

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There we go. Now it should be working.

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Just to avoid some nasty
surprises later on.