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In this video I'll tell you how you can enter boot
parameters to change the way how Linux starts. Boot parameters can be

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entered on the grip prompt and to access the grip prompt
while booting, you can press the escape key at the right moment.

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Finding the right moment is not always easy by the
way, but keep on trying. I'm sure you will get there.

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As an alternative, if a
system boot was not completed successfully,

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the next boot will automatically
show the Grub boot menu.

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So if ever you wanted to access the
Grub boot prompt and you don't succeed, just reset

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your machine while it is booting to automatically
see the boot prompt when it comes up again.

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All of the boot arguments that are entered while
booting are non persistent and mainly used for troubleshooting.

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And the main boot arguments that you can
use is systemd unit followed by the systemd

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unit unit that you want to use. Emergency
Target is for hardcore troubleshooting. Rescue Target is

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bringing you a little bit further Multi user
Target is a complete operational environment and graphical

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target is what you normally start when
you boot a graphical Linux operating system.

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Let me show you how you
can interact with this Grub boot menu.

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So I need to
start by rebooting my system.

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This is where I
need to pay attention.

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My trick is you will see a cursor
appearing when you see the cursor appearing and you

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press Escape at that moment and normally you
are all right, but that might depend on your

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distribution. No guarantees here. Again, if you can't
access the grip boot menu, just reset the virtual

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machine while it is rebooting. Here we
have all the different options for booting.

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I'm going to select Centos Stream and press Enter
E for Edit to get access to the different

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boot options. And the line that matters here is
the line that starts with Linux. That is the

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line that starts the Linux kernel. This Linux kernel
is the VM Linus file that you can see.

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Now all of these parameters are
quite okay. I don't like RHGB

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and quiet so that is already
a good start to remove them.

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And next I'm going to
use systemd unit is Emergency target.

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Now we have seen this before. If you want to start
Emergency target on a Red hat based system, you must have

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the root password set otherwise it won't work. So I'm
using Control X and then we can see what is happening.

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The problem is that this Emergency target is loading
a program with the name Sulogin which is super useful

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login. That's an additional level of protection and that
command won't work if you don't have a root password.

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From here you can do
whatever kind of troubleshooting you want.

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I happen to be not interested at all in troubleshooting, so I'm going
to reboot and I want to show you what it looks like on Ubuntu.

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Back on Ubuntu I'm also
going to use sudo reboot.

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Did you see that the cursor appeared? I
pressed escape and now I'm in my boot

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menu. Now I am going to use E
again to edit this grub boot menu there.

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We also have a line that starts
with Linux so that is looking okay.

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Well there's one thing that doesn't look okay and
that is this Quiet and splash. I really don't

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like this quiet and splash because that is
hiding what is going on while you are booting.

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I really like to see what is going on
while booting. That makes troubleshooting easier if that is required.

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Now I wanted to show you
systemd unit is emergency target because you

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need to understand how that works
on Ubuntu. As in Ubuntu the root

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user has no password by default,
so will that fail as well?

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Look at that. Ubuntu is prompting Press enter
to maintenance. The difference is at the end of

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the emergency target in Ubuntu there is no
SU login program. So I'm pressing enter and then

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I'm here in my root shell even if
the root user does not have a password.

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So that
works perfectly.