What is a Bootloader?

You may have heard that you can root an Android phone. You have also been asked to unlock the bootloader before rooting a phone. You may not have heard. Let everyone know, today we will talk about Bootloader.

First of all, Bootloader is not only available on Android phones. Any computer with an operating system has this bootloader. Computers include smartphones, tablets, laptops, and desktops.

When you activate the Power button on a computer, the first process called Power On Self Test takes place. The Power On Self Test is done to check if the computer hardware is working properly. After that, check to see if there is any bootable media on the computer. A CD? A bootable pen? A bootable hard disk? This type of search usually detects the MBR (Master Boot Record) or GUID (Globally Unique Identifier) ​​stored in the computer’s secondary memory (usually the hard drive). This MBR or GUID data is stored in the first 512 bits of bootable media.

The MBR / GUID partition tables mentioned above contain two very important information.

Partition Table
Note: In Android, the bootloader is actually stored in the / boot partition. We will post more about that later.

A bootloader is a very small program. This takes the data from the secondary memory and loads the operating system into the main memory (RAM).

Let us see some examples of bootloaders in Linux based operating systems. If you want to find out more, do an online search.

GNU Grub
If your computer only has the Windows operating system, you may not see this bootloader. However, if you have more than one Linux operating system or dual boot operating system installed, you can check the interface of this bootloader. In cases where there is more than one operating system, this bootloader will ask the user which operating system needs to be loaded into RAM. This is followed by loading the user-selected operating system into RAM and booting the computer with the appropriate operating system.

So far we have not talked about the bootloader in general on almost every computer, next we will see what the special bootloader on an Android phone looks like.

On Android phones, we can get the interface of this bootloader and do some work through it. Let’s see what this interface looks like.

If we want a key combination of the phone you can get the bootloader interface. This key combination varies from phone to model. Normally, after turning off the phone, you can boot into the bootloader by pressing two buttons at the same time like power + volume up. If you want to find this key combination, do a little search on the internet with your phone model. Will be able to find.

On an Android phone, the user will boot into bootloader mode automatically, without booting into bootloader mode manually, unless something like this happens here.

As soon as an Android phone is turned on, this bootloader checks the phone’s memory, especially the / boot partition. If you do not have the kernel when you check the bootloader, then go to / / recovery partition and check (if there is any data in / recovery, the phone will boot into recovery mode, we will talk about this recovery mode later.) For some reason. If there is no / recovery, the bootloader will not check the / system partition, because it is useless to check, because the kernel must be run before loading the OS in the / system partition.

There is no way to do that, because there is no data in the / boot partition. That’s when the phone goes into Fastboot mode. Or boots automatically into Bootloader mode or Download mode. All of these are called the same thing.

The image below shows the bootloader interface of a typical Android phone. But that interface takes a different look from model to mobile. But if done the same kind of work.

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