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Bootloader: What and what is it for?

Surely you have read or heard of this word: expressions like bootloader locked, unlock bootloader, etc ,. They are common in tutorials, but what is the bootloader for? For newcomers to the Android world and for everyone who has not yet delved into the theme, we unravel the mystery below.

Let's start from the beginning. The bootloader is a program that goes into action whenever we start our device, activating the right operating system. The bootloader is therefore not something unique to Android.

It is present on all operating system devices: tablets, smartphones and PCs. A computer, for example, can have two different operating systems (dual boot). In this case, the bootloader has the task of starting either according to the user's preference, or automatically.

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Unlock bootloader the first step to root the device / AndroidPIT

The same principle also applies to Android devices, except that in this case the operating system in question is only one. It is the bootloader that will determine when to run Android or when to enter Recovery Mode, the operating system independent operating environment located in another partition of internal memory.

Recovery Mode

Through Recovery Mode it is possible to clear the cache (the memory area where a temporary copy of data stored on a slower access medium is maintained in order to speed up data recovery) or to restore factory data without having to start the system. (A useful solution if your device has stopped responding to commands).

The bootloader is developed and supplied directly by the device manufacturer and, given its importance, is located in a memory location that cannot be easily modified by users. When wishing to modify an Android device, one of the biggest hurdles is the locked bootloader.

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Custom Recovery Example (TWRP) / AndroidPIT

What does that mean? A locked bootloader only loads operating systems authorized by a signed digital signature. Almost all smartphone makers decide to block their device's bootloader, allowing only their Android versions to load, and preventing the installation of any other custom ROMs. To give an example, with the Galaxy J7 bootloader will be loaded only the versions of Android that Samsung developed for the device.

A ROM is a compilation of the operating system that runs on your device with basic applications like calendar, calendar, camera, etc. Custom ones are those that aren't officially designed for a device, but made for it by interested people.

As you may already know, for every obstacle on Android there is a solution. To run custom ROMs like LineageOS (one of the most famous, formerly CyanogenMod), you will need to unlock the bootloader, which can then also boot "unauthorized" operating systems.

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LineageOS is one of the most famous ROMs you can install by unlocking the bootloader / AndroidPIT

For unlocking the bootloader each manufacturer chooses a method, ranging from sending a simple command via USB connection from the PC to downloading a program especially for the task. Always good to note: Just because unlocking the bootloader allows you to install unauthorized software, this operation invalidates the warranty of your device.

Attention: unlocking the bootloader may require enabling root permissions on your device. Not sure how to get them or what? Find out in the articles below:

AndroidPIT Android recovery update
This picture shows that you are messing with something delicate on your Android / AndroidPIT

Be careful not to confuse root with the bootloader unlock. Sometimes the latter may be a prerequisite of the former, but some devices may be rooted with the bootloader locked, thanks to a few tricks from the Android community.

Already had trouble unlocking the bootloader? How did you solve them?

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