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In this lesson, you'll learn about the name service switch.

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The name service switch is in the file etcnsswitch.conf, or better, etcnsswitch.conf, because after

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all it's a name service switch.conf.

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So it's used to define the order in which hostname resolution should happen.

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And it has a content like hosts, files, DNS, myhostname, meaning that it will first check

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files, which is etchost, then DNS, then myhostname.

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In this file, you can use a couple of items.

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And these are files.

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Files, in this example, has the highest precedence.

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It tries to resolve static hostnames in etchosts first.

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And if it matches, it looks no further.

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Then there is DNS, which is using DNS as specified in etcresolve.conf.

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And in this example, we have myhostname, which is using the local kernel hostname.

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Now, there's something funny about it.

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And let me show you.

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So first, I want to have a look at it, etcnsswitch.conf, where we see what?

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Well, we see hosts.

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This is the line I'm looking for.

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So hosts, files, DNS, myhostname.

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And you know what that means.

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It means that if I'm going to define etchosts, and I'm calling it 192.168.29.111,

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no, not dummyexample.com, but let's call it google.com.

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And then I'm going to ping to google.com.

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And look what happens.

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It's pinged 192.168.29.111.

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So that is funny.

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You might think it's confusing, but some people are using this to make sure that some internet-based

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hosts can never be directly accessed.