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- In this video

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I'll tell you how to manage
persistent configuration

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for network interfaces.

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Now, this is a topic where
we have huge differences

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between the distributions.

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To start it, there is NetworkManager.

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NetworkManager is what you use

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for persistent interface configuration

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on Red Hat Family Linux

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and also indirectly on Ubuntu desktop.

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We'll talk more about
it in just a little bit.

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NetworkManager has two main
utilities, which are nmtui

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and nmcli, where nmtui
is a text user interface.

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It's a nice text user
interface where you can easily

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choose your options.

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And nmcli is a command line interface.

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On Ubuntu server as well as
desktop, there is Netplan

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and Netplan is used for persistent
interface configuration.

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Netplan provides a YAML
configuration abstraction

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for various back-ends.

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Based on this YAML file,

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back-end specific configuration
files are generated.

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And now here is the interesting thing.

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On Ubuntu server, systemd-networkd is used

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as the default back-end to Netplan.

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If you would want to use something else,

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there's a network renderer
option in your Netplan

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YAML file, which can be used
to specify another back-end.

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On Ubuntu desktop, NetworkManager is used

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as a default back-end.

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Why that difference?

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Well, because NetworkManager is very good

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at managing wifi connections,
which you typically find

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on desktops and not so much on servers.

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So on Ubuntu server, systemd-networkd

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is a standard back-end
for managing networking.

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It uses one or more YAML files

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which are provided by Netplan
for the network configuration.

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So etc Netplan whatever dot
YAML is where you need to go.

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And in this Netplan configuration,

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a renderer networkd

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is used to connect to systemd-networkd.

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On modern versions of Ubuntu server,

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this is a default
setting, so you might not

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specifically find this
renderer option anymore.

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If you don't find it,

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then you are safe and
systemd-networkd is used.

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The Netplan configuration files
need to be created manually

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for persistent network configuration.

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I have an example about
that on the next slide.

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And the front end for
querying network status

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is networkctl.

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Networkctl is a part of systemd-networkd.

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And like many of the other
system, the utilities,

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it has CTL at the end of the utility name.

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So you would use commands

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like networkctl status and
networkctl up and down.

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Now how can we provide Netplan
Static IP Configuration?

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Well, you create a configuration
file that would look

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like etc Netplan 99
underscore conflict dot YAML.

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And then you can use sudo
Netplan apply to activate

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and networkctl status to verify.

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And this is what the configuration
file might look like.

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Let me type that for you.

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So here we are on Ubuntu server

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where I'm going to use

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sudo vim etc Netplan

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99 dash config dot YAML.

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So, we need to define it.

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Network version two,

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renderer networkd,

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and then we have the ethernets.

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And in the ethernets, I'm defining ens 33.

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Addresses.

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And that's the list of IP
addresses that you want to assign.

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So 10.0.0.11/24, for instance,

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or whatever you want it to be.

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Then we have gateway four,

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and that will be 10.0.0.1.

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And we can insert the name servers.

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So the name servers typically
come with a search parameter.

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My domain, comma your domain,
or whatever you want it to be.

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This is a list by the way.

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The square bracket notation
is equivalent to using list

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and every item separately in the list.

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And addresses,

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that's where we specify the
addresses of the name server.

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And there we go.

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So now, I can use sudo Netplan apply.

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And okay, it's telling us
gateway four has been deprecated,

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use default routes instead,

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but it's a warning and deprecation,

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that means that it still works.

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So sudo networkctl status is showing

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the current configuration.

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And in the current configuration,

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you can see that we have
everything that was just set.

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Now, this is how you use Netplan
on an Ubuntu server system.

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Let's also have a look
at the centOS machine

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for NetworkManager.

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So NetworkManager, that is nmcli or nmtui.

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I would advise if you need
to do this on the exam,

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use mntui.

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Nmtui is text user interface.

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And as such, it is very intuitive.

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So in nmtui, we see the connection

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and the connection is a
configuration that is connected

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to a specific network card.

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So, you typically don't want
to add or delete connections.

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You just go to edit,

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and in this edit, you find
all the options that you want.

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So by default you don't see very much,

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and that's because everything
is obtained automatically

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through a DHCP server.

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You wanna change stuff, go
to the IPv4 configuration

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and make that manual,
and then you select show,

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and then you can enter all the information

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that you want to use.

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Now this is so intuitive
that I'm pretty confident

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that you will figure
this out for yourself.

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Only one thing to realize,

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after editing a connection,
you need to activate it.

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So go to activate, press
enter, press enter,

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and then the connection with
all the new settings is active.

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Last command is nmcli.

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Nmcli is a little bit hard,

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because it's a command line utility.

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But, nmcli is awesome tab completion.

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So, as we have just seen, nmcli
is working with connection.

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So I'm using nmcli connection.

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And I'm pressing the tab key twice

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and I see all the opposite
that are available.

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So if I want to edit, for instance,

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there we go, edit, tab, tab.

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And there we can see the
different connections.

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So, I want to edit ens33.

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Tab tab is not doing anything,
so I'm pressing enter.

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And here we get the nmcli editor.

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And that's also what makes
it a little bit complex,

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the nmcli utility.

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Nmcli is powerful.

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But I would say on the
exam, don't go use nmcli.

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And if you want to use it,
man nmcli dash examples.

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This is giving you a couple of examples

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where you can easily pick
out what you wanna do.

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As I told you,

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NetworkManager is very
much for wifi networks.

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On a server, you don't wanna do the wifi,

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but you see in the examples,
there are many wifi examples.

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What you probably want to do is something

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like what you see in example 11.

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I would say,

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try it for yourself, if you
wanna know more about it,

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but on the exam, please focus on nmtui.

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That's the difference
between spending one minutes

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or spending ten minutes
on the same assignment.