Systemd Overview

Video Activity
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Time
21 hours 25 minutes
Difficulty
Intermediate
CEU/CPE
21
Video Transcription
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>> Hello there Cybrarians, and welcome back to
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the Linux plus course here at Cybrary.
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I'm your instructor Rob Goelz.
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>> In today's lesson,
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>> we're going to do an overview of systemd.
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>> Upon completion of this lesson,
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you're going to be able to understand
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the purpose of systemd.
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We're going to see how systemd really underpins
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the modern Linux operating system
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as its initialization method.
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Then we're going to use the information
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>> that we cover here to
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>> understand the rest of the module content
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that's related to systemd.
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systemd, what is it?
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Well, really systemd picks up
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>> where we left off in module 1
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>> where we were talking about
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>> the Linux boot phases in the Linux boot process,
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because systemd represents the initialization phase
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on Linux boot in modern Linux operating systems.
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systemd is a replacement for SysVinit,
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and that was the previous system
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initialization method that are used
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in older Linux distros like CentOS 6 and older.
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SysVinit is something that we will talk
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about later in this module.
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Now the purpose of an initialization daemon
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like systemd is to startup operating system services
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>> and it's going to handle which
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>> services are started and in
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what order are those services get started.
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One of the really great things about
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systemd and one of the improvements of systemd
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over SysVinit is that it
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allows for parallel booting of services.
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When you're booting things in parallel,
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that's going to allow for the operating system
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to boot faster.
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Now, the kernel phase load systemd
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during Linux boot and that kicks off initialization,
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and the systemd init process or
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daemon is always assigned a process ID or PID of 1.
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The systemd daemon is linked to from /sbin/init.
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What happens now? Well, systemd
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then launches all the other processes.
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This is part of the initialization phase,
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and it comes up and it launches all of
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these processes as child processes.
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systemd launches the processes that are
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explicitly enabled to boot automatically.
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We'll talk a little bit more about
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that as we go through this module.
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But these next processes,
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these child processes that boot from systemd get a PID
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randomly from any available numbers
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that are in the operating systems table.
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You're not going to necessarily see
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that any service is
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going to have the same PID every time.
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It's going to come up randomly as a system comes up,
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the only thing that you can rely upon having
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the same PID every time is going to be systemd,
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which has a PID of 1.
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Now in modern Linux distros systemd as
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a service manager as well as the initialization method.
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When we're talking about managing services,
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we're going to use the systemctl tool as
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a command line tool to control systemd.
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We can also use systemd-analyze
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and that's a tool that we use to find
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errors in systemd configuration and
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view state information about the systemd system.
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These components are going to be covered in
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detail over the next few lessons.
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But with that, we've reached the end of this lesson.
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In this lesson, we covered an overview of systemd,
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and the initialization phase using systemd,
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and then we get a chance to talk a little bit about
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the components of systemd.
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Thank you so much for being here,
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>> and I look forward to seeing you in our next lesson.
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