What is Fastboot?

Fastboot is a communication protocol used primarily with Android devices. It is implemented in a command-line interface tool of the same name and as a mode of the bootloader of Android devices. The tool is included with the Android SDK package and used primarily to modify the flash filesystem via a USB connection from a host computer. It requires that the device be started in Fastboot mode. If the mode is enabled, it will accept a specific set of commands, sent through USB bulk transfers. For More info, research on Fastboot

What do i need?

Open your terminal (CMD on Windows) "windows key + R" and type cmd and click enter. Run "./adb devices" (for Windows Users) while your device is powered on and unlocked. Accept the token confirmation and run again so it"ll be authorised. Linux users may need to add "sudo" for it to work. Next run "./adb reboot recovery" or ./adb reboot bootloader" or ./adb reboot fastboot and wait.

Bootloader Commands

Tip: In bootloader, you use "fastboot" instead of "adb" as the applicable name is "fastboot". Your Flashing operations here are mostly for disabling vbmeta, boot verification, flashing boot.img, logo.bin etc.

Fastbootd

Not to be confused with "fastboot", fastbootd is completely different as you flash mostly image files to their respective partitions such as vendor.img, super.img, product.img etc. You will end up here very often!

Unlocking Bootloader: YOU WILL LOOSE YOUR DATA

You can not customize your device with mods without unlocking your bootloader as this is where the device carries out it"s verification and file integrity checks. Hence, you have to unlock it, but you must also disable vbmeta. More on that later. Please make a backup of your important data before doing this!.

To unlock your bootloader, you first run ./adb devices to be sure your device is recognized, now run ./adb reboot bootloader to boot straight in to the bootloader. Note: some devices need you to reboot to recovery first and manually select bootloader before they can be recognized. Now run ./fastboot devices just to be sure. Following that, run fastboot flashing unlock and use your volume button to select "yes". In some cases, ./fastboot oem unlock also does the job. Some devices require ./fastboot flashing unlock_critical to get it unlocked. Congrats! your bootloader has been unlocked. The device will erase /data as a security protocol and boot into system. This process requires atleast 5-10 mins. Please exercise patience as the device boots up for the first time.

Overview

Device will wipe data and reboot!