The Android OS is built on top of the Linux kernel with some architectural changes made by Google. Linux was chosen as it is a portable platform that can be compiled easily on different hardware. The Linux kernel is positioned at the bottom of the software stack and provides a level of abstraction between the device hardware and the upper layers. It also acts as an abstraction layer between the software and hardware present on the device. To understand this better, consider the case of a camera click. What actually happens when you take a photo using the camera button on your mobile device? At some point, the hardware instruction (pressing a button) has to be converted into a software instruction (to take a picture and store it in the gallery). The kernel contains drivers that can facilitate this process. When the camera button click is detected, the instruction goes to the corresponding driver in the kernel, which sends the necessary commands to the camera hardware, similar to what occurs when a key is pressed on a keyboard. In simple terms, the drivers in the kernel control the underlying hardware. As shown in the previous screenshot, the kernel contains drivers related to Wi-Fi, Bluetooth, USB, audio, display, and so on.

All of the core functionalities of Android, such as process management, memory management, security, and networking are managed by the Linux kernel. Linux is a proven platform when it comes to both security and process management. Android has leveraged the existing Linux open source OS to build a solid foundation for its ecosystem. Each version of Android has a different version of the underlying Linux kernel. Currently, Google requires devices shipped with the Android 8.0 Oreo OS to have at least Linux kernel version 4.4.