Instructor: In this lesson,
we're going to talk about boot issues.
Now, when your computer first starts up,
it's going to go through its power on self-test.
And once that successfully completes,
it's going to look for a boot device.
This boot device could be an internal storage drive
such as a solid state device, or an internal hard drive,
or it could be removable media
such as a USB flash drive or a CD or DVD.
In addition to this,
you can also boot up over the network.
And so, all of these are different ways
you can boot up your system.
But what is important
is that if your system cannot find a bootable device,
it's going to actually cause an error
because it doesn't have an operating system to load.
When this occurs, you're going to get an error to the screen
that says bootable device not found.
So, how can you solve this?
Well, there's a couple of different things
you need to look at in order to solve this boot issue.
First, you can go into the UEFI or BIOS
and look at your boot order.
Inside of your UEFI or BIOS, you're going to dictate exactly
how you want the devices to boot and in which order.
For example, the order I just presented in this lesson
is actually a pretty common order
where it's going to look for an internal storage device first
like a solid state device or an internal hard disc,
then it's going to look for any kind of removable storage
such as a USB flash drive or an optical disc drive
or even an old school floppy disc drive.
And then it will look to the network
as its final boot option.
You can change this order
based on the priority you assign it
inside of the UEFI or BIOS.
Then you should check and make sure those storage devices
are being recognized by your computer
inside the UEFI or BIOS.
If they're not being recognized by the UEFI or BIOS,
this could indicate that the storage device
isn't properly connected to the motherboard
or does not have the proper amount of power
being applied to it.
So, you want to make sure you check the connections
on that storage device
and make sure it is properly cabled and connected.
Once you validate that the UEFI or BIOS
is recognizing the storage device,
then it may indicate that you have a boot sector issue.
Now, the boot sector is the first area
on that storage device that's going to be read from
by the UEFI or BIOS when you're booting up the system.
This helps the system determine
what the partitions are on that given storage device,
so it can then assign drive letters to it
and interact with those partitions.
Now, there are two different ways
that you can format your storage device
and be able to provide that boot information.
This is known as the Master Boot Record or the GPT
or GUID Partition Table.
The Master Boot Record, also called the MBR,
is a legacy method of providing the boot information.
When you're using the MBR,
this is going to be stored in the first sector
of the first partition of that storage device.
Now, when I talk about a partition on a storage device,
I'm talking about taking an entire drive
such as a one terabyte SSD or hard disc drive
and splitting it up into multiple logical parts.
Each of these parts is called a partition.
Now, you can have a single partition
or you can have multiple partitions.
It just depends on how you want to configure your system.
If you're using Windows,
most of the time you're going to have a single partition
but if you're using a Linux system,
you may have multiple partitions
that are separating out the system files
versus the data files and things like that.
Now when you're using this legacy Master Boot Record format,
it's going to store information about all the partitions
in that first sector of the storage device
as well as some information
that's going to point to the location
of the first bootable partition,
which is going to have the active boot sector.
So, when your system tries to boot up,
if you're using a Master Boot Record type system,
it's going to read that first sector,
get the information about the partitions,
figure out where that active boot sector is,
and then move over to that active boot sector
to be able to find and load an operating system
using a boot loader.
Now, depending on what operating system you're going to use,
you're going to be using a different boot loader.
If you're using Windows,
you're going to be using the Boot Configuration Data,
also known as the BCD,
to be able to store the information
about a Window systems and how to boot it up.
If you're using a Linux operating system,
you'll most likely be using GRUB
or LILO as your boot loader.
Either way, though, the concept is the same.
We're going to boot up the system, find a storage device,
read the first sector on that storage device
which contains your Master Boot Record,
and then point to the boot sector on the active partition
to be able to load up a boot loader
and load that operating system.
Now, the second way you can format your storage devices
with boot information
is actually what we use in modern systems,
and this is known as GPT or the GUID Partition Table.
Now, GUID stands for the Globally Unique ID
and the GUID Partition Table is a specialized boot scheme
that has a lot of modern advantages
over the MBR or Master Boot Record.
For example, you can have larger size partitions
and you don't have to necessarily boot
from the first partition
like you do with the Master Boot Record.
When you're dealing with the GPT boot schema,
you're instead not restricted to that single sector
but you can actually save that boot information
on any of the different partitions that you want
and be able to have a different way
of identifying the partitions.
And instead, you can move that boot information
to other sectors on the hard drive.
But the idea is the same.
We still need to be able to identify
the different partitions on that storage device
and then find an operating system to boot
using an operating system boot loader
on one of those active partitions.
So, when you're looking at a storage device,
if it's being detected by the UEFI or the BIOS properly
but you're not able to find a bootable device,
that usually indicates that there's a problem
with the Master Boot Record
or the GUID Partition Table known as the GPT.
Most commonly, you'll see the error message
as bootable device not found but in some cases,
you may see it say OS or operating system not found
or even invalid drive specification.
All of these tend to indicate the same thing.
There is some kind of a problem
with the boot sector on that storage device.
Now as a technician,
when you have one of these type of issues
with the boot sector that is corrupted,
you're going to have to understand
how to correct that boot sector
and be able to restore the operating system.
Now, because that is specific
to a specific operating system version,
we're going to save that type of troubleshooting
for Core 2 of the A+ exam because here in Core 1,
we are focused more on the hardware
and not the operating systems.
Instead, you just need to be able to identify
that the boot sector is corrupted
and then in Core 2,
we'll figure out how to solve that problem
based on the different operating systems
that you may be using.
All right, now that we've talked all about
boot sectors and the Master Boot Record
and the GUID Partition Table,
let's take a look at another type of boot issue
you might experience.
I mentioned earlier that your UEFI and BIOS
is going to set a prioritized boot order
based on what you've set in its configurations.
Normally, it's going to look at your internal disc first
but if you have those priority orders changed up,
you may be looking at removable storage media first
like a CD, DVD, or USB thumb drive,
or even the network first
and then going to your internal storage drive.
Now, this can cause a lot of problems for your users
because if you have the prioritized order set incorrectly
and you have it set for something
like your optical disc drive first
and somebody left a DVD in there
with a live Linux distribution, if you reboot that system,
it's going to boot from that DVD first
and load up Linux instead of Windows
that they're expecting from the internal hard disc.
So, you need to keep this in mind as well
because if you have the boot priority incorrectly set,
you can actually boot from an external device
or the network instead of the internal disc
and that can load up an operating system
that your user is not expecting.
Now, the final thing I want to mention
when you're troubleshooting boot issues
is that you always want to be able to see
if your internal storage device
is actually operating properly
by looking, listening and feeling
if that device is in motion.
Now, what do I mean when I talk about looking,
listening, and feeling that storage device?
Well, if you look at the front of your computer,
there's going to be an LED activity light.
And when you power on the system,
you should see drive activity
and that LED should be blinking
any time data is being accessed
to or from that internal disc drive,
whether that's a hard disc drive or a solid state drive.
That's what I mean by looking.
Now, when I talk about listening and feeling,
this will not work
when you're dealing with a solid state device
but it will work with a traditional hard disc.
When you're using a traditional hard disc
and you're reading or writing information,
you can actually put your hand on the case
next to where that hard disc is
and you'll be able to feel if that disc is actually moving
because that disc is going to spin
when data is being read or written to it.
Again, you can also listen for this
because you'll hear that worrying sound
of that hard disc drive moving around
as the seek head is trying to read information
from different parts of the disc.
So, when you boot up the computer,
if you're not hearing that hard drive spinning
or you're not feeling the vibrations
when you touch the case,
this can be an indication
that that drive is not being properly recognized
or properly powered by the system.
And so in this case, you might need to shut down the system,
open up the case,
and verify that it is properly cabled and connected
to the motherboard and the power supply
to ensure that hard disc drive is ready for use
and you'll be able to boot your operating system from it.