Exploring the Boot Procedure

Change Grub Runtime Parameters

here you can see the regular kernal and rescue kernal

after pressing e:

• that means kernal can immedietely access your root directory even without using /etc/fstab
• ofcourse it doesn’t use /etc/fstab. because thats a file on the root volume
• remove rhgb quiet line and press ctrl+x

• this allow you to see what’s happening while booting

Change Grub Persistent Parameters

• how to decide you have a EFI system or mbr system?

lsblk | less

if your boot disk only has the boot disk without efi then you are running mbr

I’ll show you how to manipulate Grub2 runtime parameters.

So from the Grub2 boot menu,

you can press E to edit runtime boot options

to the line that starts with Linux.

Like for instance, systemd.unit is emergency.target

or systemd.unit is rescue.target.

Also, you can access a more advanced editor,

but it’s a little bit more complicated.

If you press C, then you enter the Grub2 command mode.

And from the command mode,

you can manually start everything yourself.

That’s pretty hard, but if you really want to try,

type help for an overview of available options.

Let me show you.

So here, we have the Grub boot menu.

In the first entry, we see the regular kernel.

The second line is for the rescue kernel.

That’s not what we need.

We need the regular kernels.

So, I’m pressing E to edit the regular kernel.

It is this Linux line that really matters,

because the Linux line defines

how the kernels should be booting.

So, it identifies the name of the kernel.

It identifies the name of the root volume.

And that means that the kernel can immediately access

your root directly even without using etc/fstab.

Of course, it doesn’t use etc/fstab,

because that’s a file on the root volume.

And before being able to access it,

kernel needs to know about the root volume.

So that’s why you see it here.

To the end of the line, we see rhgb quiet,

and that is really something annoying.

I would advise, take that out.

And then you use CTRL X to start,

and that allows you to see

what’s actually happening while booting.

Now, there’s so much more that you can do

to modify runtime parameters.

We’ll talk about it later.

For now, I am going to log in again,

so that in the next video,

I can show you how to change precision parameters.