Name Server (Demo)

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Time
21 hours 25 minutes
Difficulty
Intermediate
CEU/CPE
21
Video Transcription
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>> Hey Cybrarians and welcome back to
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the Linux plus course here at the Cybrary.
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I'm your instructor Rob Goelz and in today's lesson,
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we're going to be discussing Name Servers.
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Upon completion of this lesson,
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you are going to be able to explain
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the importance of name servers,
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describe at a high level how a name server works.
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Then we're going to perform a basic installation of
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the name server role in both CentOS and Ubuntu.
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All of us probably know that we can get to
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Google by going to www.google.com.
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But who knows the IP address or range of
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IP addresses that are used to get to google.com?
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The answer is none of us. None of us know.
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>> We don't need to.
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>> We use the Domain Name Servers or DNS,
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and that translates the IP address to the host name.
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We go to google.com and we get
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the IP address from DNS. No worries.
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One important thing to know,
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DNS uses port 53.
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This is another one of these ports that's
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probably going to be asked about on the exam.
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It's a commonly used port, DNS port 53.
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In Linux, when we're talking about DNS,
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we're generally talking about the Berkeley Internet
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Name Domain or BIND package.
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BIND is used to provide DNS name server
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services when we're in Linux and BIND is pretty old.
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It's been around since the 80s.
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It came around with the first BSD release,
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or rather one of the earliest ones, BSD 4.3.
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A name server in this case has authority over
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a space or portion of
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a domain and that's known as the zone.
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For example, a name server may
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have authority over cybrary.com.
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Clients are configured to use the name server
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>> when they wanted to host name resolution.
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>> If we want to get the IP address of a host name,
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we go to a name server,
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and these are generally stored in the etc/resolv.conf.
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Those entries next to resolv.conf just
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point to a server that is running
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a BIND package or something like that.
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Now host name request to the name server are
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resolved for requests in the zone.
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In other words, if that name server
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>> handles cybrary.com,
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>> it's going to answer for any requests that we have
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about host names that are in cybrary.com.
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But if we're trying to query
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the hosts or the host name server,
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we're trying to get host names from
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the name server for cybrary.com,
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and we're saying, "Hey, cybrary.com,
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name server we want to know about Google."
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It doesn't know about Google. It has to go to
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another name server that's called a referral.
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But with that, let's go ahead and see how a name server
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is installed with some demo time.
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Here we are in our demo environment.
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In first of all, we're going to get started in CentOS.
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In order to install,
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BIND in CentOS, it's real easy.
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We do DNF, install,
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BIND, B-I-N-D, and there we are.
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We'll go ahead and install
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this package and once it's installed,
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let's do the same thing we've been
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doing the past couple times.
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Let's take a look at all of the files that installs.
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Then hit Control L to clear the screen.
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Then we're going to do an RPM QL
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on BIND and pipe that to less.
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Now we can see that quite a bit of files
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get installed with BIND when you're in CentOS.
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Now the configuration file that we
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want to look at when we're talking about
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BIND its CentOS is
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fc/named.com because the domain for BIND,
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is actually called named.
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If we look in here,
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probably the most important thing we're
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going to see is listen on port 53.
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As I said, DNS uses port 53.
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There are a ton of configuration options
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>> available here.
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>> But going through this named.com
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files beyond the scope of Linux plus exam.
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Let's go ahead and just quit out of
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that and we'll move over to Ubuntu.
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Here we are in our Ubuntu environment.
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It's just a little bit different.
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Here in Ubuntu, obviously we're going to
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use app instead of using DNF,
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but also to install BIND,
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there's quite a few things we have to install here.
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I'm just going to copy and paste this
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in from my side of things here,
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just to save us some time,
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we're going to be installing BIND9,
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>> BIND9-doc and DNSutils.
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>> Let's hit Enter on that and now
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we're going to download and install that stuff.
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In this case, it's already installed on the system.
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We're good to go there.
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Let's take a look at what's been installed.
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We did a Dpkg,
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L, for BIND9,
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and then pipe that to less and
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we can see all of the stuff that's
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installed for BIND on the Ubuntu system.
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Again, keep in mind when you're talking
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about installing on CentOS,
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you just install BIND.
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When you're talking about installing on Ubuntu,
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you install BIND 9,
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BIND9 utils package,
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BIND9-docs and DNSutils
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>> to get everything installed there.
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>> Let's take a look at the configuration file in Ubuntu.
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That is found at etc/bind/named.com.
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But look at this, this file
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actually references three other files.
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Hopefully by now you're noticing this is
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part for the course when you're talking about Ubuntu,
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they like to store a different configuration
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>> in lots of different files
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>> throughout the operating system.
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>> Let's quit out of here,
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and let's take a look at one of those.
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We'll look at etc/bind,
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and we'll look at named.conf.options and there we are.
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In this file we can see that the server is listening
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on IPV6 really for any DNS requests.
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Again, in all of these files,
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you can go through each one of
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these files individually if
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you have the time and inclination to do so.
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But these files have
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a ton of configuration options available,
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and that's beyond the scope of Linux plus exam.
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With that, we've reached the end of this lesson.
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In this lesson, we covered
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the importance of name servers.
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We talked a little bit about how a name server works,
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and then we did a basic BIND installation
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in CentOS and Ubuntu.
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Thanks so much for being here and I look
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forward to seeing you in the next lesson.
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