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- In this video, I will show
you how to work with systemD.

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So I have a couple of commands
that I want to show you.

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And here, we can see the commands.

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Let me just show you.

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So, as I mentioned, systemD
is managing many things.

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We use systemCTL, which is the main

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systemD management command minus T help.

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That will show you the
different unit types

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that it can manage.

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And amongst these unit types,

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you have the service
as the most important.

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But it can mount file systems.

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It can take care of devices.

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It can open network sockets.

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It can do so much more.

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If you wanna get an
impression of everything

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that it is doing, use systemCTL.

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And before we do anything else,

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let's do the tab completion.

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Here you can see all
the different commands

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that you can use with systemCTL,

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including list-unit-files, for instance.

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What is that doing?

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Well, that's showing all
the different unit files

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that are used on your system
and their current status.

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Nice to see what systemD is managing.

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But we should not explore
this in much detail right now,

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because, as you can see,
382 unit files in total.

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That's kind of impressive.

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If you wanna know what
is happening right now,

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then systemCTL list-units is
the best way to figure out.

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That is showing the
units currently loaded.

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And as you can see,

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it starts with a bunch of devices.

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After the devices you have the mounts.

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And yes, that is true systemD
is taking over the work

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of etc fstab, it's taking
care of the mounts.

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And here we can see the services.

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Now let's take the cups service,

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just a random service as an example.

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We can see that the service is loaded,

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it is active and it is running.

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So loaded means that systemD
is aware of the configuration.

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And active means that
it is currently active

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And running means that
the state is running.

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That's not always the same

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because you can also have
a service that is active,

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but in a state of exited,

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as if the service has done its work

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and it's already done with it.

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Now, the most important things

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in systemD is service management.

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And in order to show you,

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I'm going to install a software package.

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So sudo, DNF install minus Y HTTPD.

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That's installing the HTTP web server.

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I don't care about the
HTTPD web server here,

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but I need an example.

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So I just installed the web server

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and I'm going to use sudo
systemCTL status on HTTPD

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to figure out the status of this server.

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Now, what do we see here?

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We see that the service is loaded.

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Loaded means that systemD is aware

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of the configuration file.

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The configuration file

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is usr/lib/systemD/system/HTTPD.service.

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It is disabled, which means
that it is not enabled

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for automatic start at system boot.

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And we also can see that
it's inactive and dead.

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Now let's change this and
let's do a start on HTTPD.

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Now I'm using status again.

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And what do we see?

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A whole lot more information.

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We can see that it is active.

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We can see information
about the documentation,

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but also information
about the process IDs,

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about the memory that it's using,

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and even information from the logs.

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This is what makes systemD so cool.

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Services write the log
information directly to systemD.

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And if you use systemCTL
status to get information

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about your service, you
automatically see that.

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One more thing to be noticed.

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And that is that the
service is still disabled,

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which means that it's
not going to be started

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automatically at system start.

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And if you don't like that,
well, we are just going to use

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systemCTL enable on the service.

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Enable means that the service is added

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to its default environment.

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And this default environment is a target.

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The target defines the state
that the system is starting in.

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And here we can see multi-user
target to which it is added.

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We will talk about it later in just a bit.

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If you use systemCTL
status on HTTPD again,

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now we can see that
everything is configured.

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The service is enabled,
the service is active

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and it is running and we are all good.

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Now you can also do the opposite,

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and that will be sudo
systemCTL stop on HTTPD.

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You can probably guess what
is happening if you do that.

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And that's right, we just stopped it.

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Now, by stopping it we can still see

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the relevant information,
including log information,

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because after all this
thing has been active.

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And that is quite kind of useful.

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You don't have to explore
any log files anymore.

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All the information that
you need is right here.

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Now, this is a very important
part of working with systemD,

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management of these services.

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There is more, and we will
find out more about it

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in the next couple of videos.