Bootloader Phase: GRUB2 Bootloader

Video Activity
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Time
21 hours 25 minutes
Difficulty
Intermediate
CEU/CPE
21
Video Transcription
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>> Hello Cybrarians.
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>> Welcome back to the Linux+ course here at Cybrary,
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>> I'm your instructor, Rob Goelz.
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In today's lesson, we'll be learning
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about the GRUB2 Bootloader.
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Upon completion of this lesson you'll be able
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to explain how the GRUB2 bootloader works.
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Now, GRUB2 is a grand unified bootloader version
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2, catchy name.
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It is the replacement for GRUB.
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Any version that is newer than 1.98 is GRUB2.
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You can find out what version of GRUB you're
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using by running one of the following commands.
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You can see on the right-hand side here we
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have Ubuntu prompt and a CentOS prompt.
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You can run grub dash install space dash capital V
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on Ubuntu and it will return
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the result as to what
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version of GRUB that you're running.
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But if you're on CentOS,
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you use GRUB2 dash install space dash V.
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This will be one of the most fun things
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that you have to deal with when you work with Linux.
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How do you find out what version of GRUB you're running?
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It depends.
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Get used to these two words,
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it depends, you're going to hear them a lot.
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But you can use one of
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these two commands to determine what version
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of GRUB you're running depending
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upon what distribution you're using,
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whether you're using Ubuntu or
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CentOS or some other Linux distribution.
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In our case, we can see that both of these are
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running 2.04 or 2.03,
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that's higher, 1.98,
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so we're running GRUB2.
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Now, GRUB2's menu is a
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little bit different to configure.
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There are actually two places that
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GRUB2's menu is configured.
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The first one is SE default GRUB,
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which controls configuration variables
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, so GRUB time out.
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How long does that mean you stand for,
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five seconds in this case.
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We can also display things about
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the command line that you see on the Linux system,
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whether or not you can recover grub.
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Then you also get into the GRUG directory.
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That's where you can build customization around
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that GRUB menu and there are scripts in there
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that are used to build the GRUB menu by default.
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Now, if you wanted to change
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GRUB2 what you would do is you can
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edit SE default GRUB
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and you can make the modifications in there.
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You can also create a custom script,
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as I discussed previously in that /etc/grub.
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d directory.
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But once you make changes to GRUB2,
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it'll get you to save them and everything is hunky-dory.
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You have to go and execute
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a command and that command is called GRUB2-mkconfig.
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Once that's run, the changes get picked
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up and when you get rebooting,
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again, you'll see those changes in the next boot cycle.
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We will go deeper into these files in the next lesson.
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Now, just like we saw with GRUB,
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GRUB2 has an interactive boot.
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When you get to that splash and hit
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Escape and get in and modify
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things as need be and you can see
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all those lovely commands that I've noted there.
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Go ahead and feel free to pause and read through those,
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but we can go ahead and move on and get moving forward.
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In today's lesson, we covered the GRUB2 bootloader.
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Thank you for being here and I look
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forward to seeing you in the next lesson.
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