Time
8 hours 30 minutes
Difficulty
Beginner
CEU/CPE
10

Video Transcription

00:02
all right. Hello and welcome to module 102 dot to we talk a little bit about
00:07
boot managers
00:09
now, historically, the grub
00:12
a grand unified boot loader
00:15
was links, uh, was legs default boot loader
00:19
grub to came along a little bit later and was a replacement with some nice new features.
00:25
So we'll talk about both these a little bit
00:27
and see some of their configuration steps.
00:31
And we'll also review some of the comedians that are needed in order to make changes to the loader configuration so that you can have multiple kernels to choose from and do some other customers Asians.
00:45
And when you're booting Olynyk system, you might want to specify alternate boot locations.
00:51
You can do this by creating a bootable image on the thumb drive.
00:55
So using the D D command, as we see here,
00:59
you can actually transfer the ice so image to a thumb drive and then boot from that once the system is reset.
01:07
That's a nice, huh?
01:08
We have a portable method of building new systems out on the floor and that kind of thing,
01:15
but it's also nice because you can have alternate
01:18
boot images that you wanted to select from when you're
01:22
doing different kinds of trouble shooting and so on.
01:25
Once I've got more than one colonel configured, I can then
01:30
choose them from the grub menu, and we'll see a little bit more details on how that set up here shortly.
01:36
But this again is another nice feature. If I build a new colonel
01:38
that I want to test some settings, for instance, I can configure grub to have that available to me as an alternate choice when I boot.
01:46
This way, if the new colonel doesn't work, I can always revert to the previous one and get back to a operable system.
01:55
Now you should know a little bit about legacy grub
01:59
and grub, too, of course.
02:00
But what is the boot loader actually do
02:04
in politic sense for grub and grub to what happens is the boot loader is in two pieces. First, we, uh, the BIOS loads. The first stage,
02:13
which we can see here, is a very small amount of data, only 512 bytes.
02:17
But that's enough information to get the second stage loaded, which actually
02:21
loads the Colonel and begins to a low. The operating system into memory.
02:27
Now, when this,
02:29
uh, boot loader is installed,
02:31
it coordinates all of these actions for the two different stages and begins the process of trying to get the root file system mounted.
02:40
Now, as you'll see on the right side here, we have several different choices for boot loaders
02:46
for the purposes of the exam grub grub to are the main ones that you should be aware of.
02:52
But there's also the legacy of bloat er of Lilo.
02:55
There's even a lie low, which is for ah, you fi systems. Slightly different hardware characteristics
03:01
are available there,
03:04
and then system commander insist Lennox, and there's probably a handful of others that that might also exist. But there is some of the main ones that you would expect to encounter
03:14
now, if we look at some of the steps
03:16
for configuring grub
03:20
now, grub is no longer support it. Uh, you can't even get the files from repositories. There might be some websites that still have a legacy repositories,
03:30
so you should know a couple of details
03:31
about installing this,
03:34
and we see the basic steps here so
03:37
you can investigate this slash Boots last grab menu
03:40
and that will show you some of the configuration options if you had rub installed
03:46
or ah, underneath slash boot grub. We have the grub dot com file
03:52
and you'll see that there's a lot of similarity with
03:53
the previous version of grub in the new version as faras follow naming and so on.
03:58
And then we can simply just run the grub, install command
04:01
for the drive in question.
04:03
Uh, typically Dev sda scuzzy disc A.
04:10
So because this is no wonder supported, there's probably not much need for
04:15
using grow many longer, since grub to is the better replacement has been redesigned,
04:19
and
04:21
the install an update process is very similar.
04:25
In this case, the configuration file is boot group to grub duck and fig,
04:30
and the first partition number changes from 0 to 1
04:34
minor minor differences. Really,
04:38
you can also
04:40
select for multiple Colonel's using grew up, too, just like you can with regular grub
04:46
and the convict files can be I didn't manually,
04:48
and then we can see how that
04:50
how some changes we would make there could be exported to new config file so that you can reboot and
04:57
huh
04:58
see those changes in the fact for your system.
05:02
Now grab Legacy has some
05:09
coming options for how you want the menu to look how you want to operate.
05:14
For instance, you can specify a title for different kernels that you've configured. This could be handy.
05:19
Instead of trying to scrutinize some small difference in a configuration of the colonel,
05:26
you know the numeric portion of the name.
05:30
Why not give it a label or title to make it easier to figure out which one it is that you want to select? It could also pick your own customized image during during the boot process.
05:40
You could even set a password to protect the grub. Man, you protect the booting process.
05:45
That's pretty good if you want to tighten security,
05:47
Uh, and you and you probably can find some procedures to do that,
05:51
you're more interesting the security aspect of
05:55
controlling your system.
05:58
But as we saw in the previous screen, the install commands very simple, straightforward,
06:03
and then we can just run the grub, make config command, as we see here
06:09
to generate the new CONFIG file,
06:12
and one second Vic Falls is created. We can go look at it and see what changes
06:16
are evident
06:20
by focusing for a moment more on grub, too.
06:25
We're going to go to the process of looking at the convict file here and updating the configuration with some some changes that are possible and then
06:33
look at the evidence of that update.
06:38
So go ahead and switch.
06:46
Okay,
06:47
So first, let's look at our
06:50
config file
06:53
and what we can see here. I've actually added a few lines just to show some of the options that you might wantto modify one of the things that people like to change. Typically as the time out,
07:02
five seconds is a little bit short,
07:04
so I'm gonna change that to 10 seconds.
07:09
Now the group default is the colonel.
07:12
That's the last saved version. That's what specified right now. When you see that
07:16
thought
07:17
default is equal to saved,
07:19
that's typically what you want. But I could also a sign, uh,
07:25
in America value like zero through five or whatever it is
07:29
by specifying a number here. So grab default equals zero up. Defaulting was one and so on
07:35
mind. My third option is to actually use a label like New Colonel or,
07:41
you know, when you're when you're making colonel changes as I mentioned a few minutes ago. It's always a good idea to
07:47
label it or make some other kind of notations. You know, this is the new colonel, and then you can easily revert to the previous one, have needed for some reason.
07:57
And then we have the actual command line that's used were in the system boots.
08:01
So it tells our system to automatically save Colonel crash information
08:07
where my logical value manager details are also the fact that I want my system to be booting and quiet moment, which means on Lee show me critical colonel related messages.
08:20
Souls. Convict changes are pretty pretty basic, uh, things that you can do
08:28
gonna save that fall
08:33
And now, once, Once I've edited the config file,
08:37
I want to verify a couple things before I build a new colonel. One is two.
08:43
I want to look at my
08:46
grub config file.
08:52
I'm sorry I'm not the config file, but the device map.
08:56
And when I'm sure that it points to the correct disc cells, we can see here.
08:58
Grubs now
09:01
configure at what was already configured. But I'm just verifying That's configured for Dev Scuzzy disc A. That's what I want.
09:09
Now I can run the install command
09:11
on that disk
09:16
and finished with no error. So that's good.
09:18
And lastly, I can update my convict fall. So now I run grub to make config
09:26
supposed to find the output.
09:33
Yeah, there we go.
09:37
So now my my conflict files updated. You can see all the details of that new current line just generated,
09:43
um,
09:45
and start the new grub conflict that I just generated.
09:46
Now, I didn't change anything important, but, you know, adding 10 are changing the menu 10 seconds. Maybe making some other kernels available with label might be something really useful.
09:58
Now, if I look at
10:01
I can't talk today,
10:07
I can see that that file has just been updated
10:09
about a minute ago.
10:13
So very easy to want to deal with.
10:16
And
10:18
once we're done with that, we may want to also think a little bit about how the boot loader interaction works. And it will demonstrate this here in a moment since I've changed the menu, I want to be able to reboot and see those changes.
10:28
But once I'm in that man, you have got my 10 seconds to interact with screen I can use my arrow keys or I can click a name if it's a virtual machine
10:37
and the Iraqis like to go up and down and select the colonel that you want to work with
10:41
or I can use eat out of the configuration if I need to make some changes. There's some things you don't want to do there for recovery purposes, for instance,
10:50
and I can get into the command prompt.
10:52
So let's go ahead and see what that looks like.
11:00
So do a shut down
11:03
miners are. No.
11:07
I shall do this differently than I do in a Net six.
11:13
It's an alternate way to reboot.
11:16
Good to know that all the different options
11:20
All right, so now this you'll notice that the counter You might have seen it very quickly, but at the bottom of that menu, you should have seen the counter. It started on a 10 seconds and started counting backwards down to zero.
11:33
So this is the latest colleges created. I still have a rescue colonel here,
11:37
and you notice that I can
11:41
and eat at it.
11:43
This particular line
11:45
and it's a very simple editor of kind of like note pad you just move your cursor around with your arrow keys
11:50
and
11:52
make your appropriate changes.
11:56
So I see some insert kernel module commands here.
12:05
There's also the line that shows the actual colonel being loaded. So there's
12:11
that makes 16 and all the different parameters specifying where route lives
12:16
or the crash colonel settings are, and so on.
12:22
Now. I could escape to discard my edits, so don't want to save anything there.
12:26
I could also had seating in my command prompt
12:31
and escape. Get you back out of
12:35
the grub shell.
12:37
I want another group shell. I've got a lot of different options here.
12:41
I just talked. Helped Thio see what some of the commands are that are available to me.
12:48
It's quite a few options there,
12:56
and I can do this for a single command. If I want Thio,
13:01
see how it actually operates Aiken boot operating system from different images that I might have available.
13:07
I've got up
13:09
other options to think about here, like
13:13
making changes to my time and date in case that I'm in the motor ride. That's the most important way for me to do this in the safe way to do this
13:22
I can also define
13:24
different colonel settings different characteristics that I want to
13:28
to use.
13:30
But just knowing how to get into the shell is the main thing as faras
13:35
what you're, uh,
13:37
doing with the colonel for the exam purposes.
13:41
Now, to get out of this menu, I can just escape.
13:46
I can also get a I can also just hit enter here and go ahead and boot from that colonel.
13:54
So it's important to play around the settings. There's a little bit of customization as we saw
14:01
and know how to use the
14:05
It is the Legacy Command to install the Colonel
14:07
stall group crab rather or to install grub too.
14:11
So we saw making fig install command
14:16
and also verified that we can write those changes to an output file convict file reboot, and then see that they're actually effective.
14:24
All right, so that gets us to the end of the boom Andrew section. I'll see you in the next module.
14:31
102.3. What? We talk about sharing libraries.
14:33
Thank you.

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