Bootloader Phase: GRUB Bootloader
Video Activity
Join over 3 million cybersecurity professionals advancing their career
Sign up with
Required fields are marked with an *
or
Already have an account? Sign In »
Video Transcription
00:00
>> Hello Cybrarians, and welcome back to
00:00
the Linux plus course here at Cybrary.
00:00
I'm your instructor Rob Gills.
00:00
Today, we're going to be discussing
00:00
the bootloader phase,
00:00
and particularly, we're going to be discussing GRUB.
00:00
Upon completion of the lesson,
00:00
you'll be able to explain
00:00
>> how the GRUB bootloader works.
00:00
>> Now, GRUB actually stands for GRand Unified Bootloader.
00:00
It's not the little creepy crawly
00:00
you see over on the left-hand side.
00:00
It is the legacy bootloader that
00:00
is used to bring up a Linux OS.
00:00
The purpose of GRUB and all bootloaders is to load
00:00
the Linux system kernel GRUB operates in stages.
00:00
Those stages are stage 1 and then is where
00:00
that Bootstrap we saw
00:00
finds GRUB on the master boot record,
00:00
and it points to either stage 1.5 or stage 2.
00:00
Now, GRUB may go to stage 1.5,
00:00
right after that master boot record sector,
00:00
before the first partition if it needs
00:00
specific file system drivers.
00:00
If you're loading something wackier,
00:00
you're using an older version of Linux
00:00
>> that doesn't have the drivers that you need to
00:00
>> boot up that particular file system,
00:00
you're going to go to stage 1.5, do not pass go,
00:00
do not go to stage 2 before you get that loaded.
00:00
From there, you will go to stage 2,
00:00
which is stored on that first partition,
00:00
and that presents the text menu we
00:00
saw a couple of times now like
00:00
a new bootloader menu and that gives
00:00
us options for selecting a kernel image.
00:00
Now, the GRUB menu is configured.
00:00
What we see in them and use
00:00
configured from one of two files,
00:00
could be in grub.conf, or menu.lst.
00:00
The default configuration file
00:00
is actually /boot/grub/menu.lst,
00:00
but some distributions actually use
00:00
>> /boot/grub/grub.conf.
00:00
>> GRUB still thinks it's using menu.lst,
00:00
but really it's linked to grub.conf.
00:00
We can see in the right-hand side here,
00:00
if you've seen the blue menu.lst,
00:00
there's arrow point to grub.conf
00:00
>> that's known as assembly.
00:00
>> We'll get into that later as we go through the course.
00:00
But that is pretty much what we need to
00:00
know about the menu from here.
00:00
We're going to cover the grub.conf
00:00
file in depth in a few lessons later.
00:00
Now, the GRUB system allows
00:00
>> you to boot up interactively,
00:00
>> allows you to go in and change the way that
00:00
you're going to boot into the system.
00:00
The way that you can do that is by when you get to
00:00
that GRUB boot menu, hit Escape.
00:00
Then from there you can hit
00:00
the arrow keys to move down in between your lines,
00:00
hit Enter to select the current line,
00:00
and do all those wonderful things over there.
00:00
I want to enumerate all of them
00:00
here to save you some time,
00:00
but hit pause, look over those.
00:00
If you have time on your own system,
00:00
please go ahead and play around with it.
00:00
But with that being said in today's lesson,
00:00
we cover the GRUB bootloader.
00:00
Thank you for being here,
00:00
and I look forward to seeing you in the next lesson.
Up Next
Instructed By
Similar Content
