Unified Extensible Firmware Interface is a specification that defines the architecture of the platform firmware used for booting the computer hardware and its interface for interaction with the operating system. Examples of firmware that implement the specification are AMI Aptio, Phoenix SecureCore, TianoCore EDK II, InsydeH2O. UEFI replaces the BIOS which was present in the boot ROM of all personal computers that are IBM PC compatible, although it can provide backwards compatibility with the BIOS using CSM booting. Intel developed the original Extensible Firmware Interface (EFI) specification. Some of the EFI's practices and data formats mirror those of Microsoft Windows. In 2005, UEFI deprecated EFI 1.10.
The USB mass storage device class is a set of computing communications protocols, specifically a USB Device Class, defined by the USB Implementers Forum that makes a USB device accessible to a host computing device and enables file transfers between the host and the USB device. To a host, the USB device acts as an external hard drive; the protocol set interfaces with a number of storage devices.
The boot ROM is a type of ROM that is used for booting a computer system. There are two types: a mask boot ROM that cannot be changed afterwards and a boot EEPROM, which can contain an UEFI implementation.
Das U-Boot is an open-source boot loader used in embedded devices to perform various low-level hardware initialization tasks and boot the device's operating system kernel. It is available for a number of computer architectures, including 68k, ARM, Blackfin, MicroBlaze, MIPS, Nios, SuperH, PPC, RISC-V and x86.
A live USB is a portable USB-attached external data storage device containing a full operating system that can be booted from. The term is reminiscent of USB flash drives but may encompass an external hard disk drive or solid-state drive, though they may be referred to as "live HDD" and "live SSD" respectively. They are the evolutionary next step after live CDs, but with the added benefit of writable storage, allowing customizations to the booted operating system. Live USBs can be used in embedded systems for system administration, data recovery, or test driving, and can persistently save settings and install software packages on the USB device.
The Linux booting process involves multiple stages and is in many ways similar to the BSD and other Unix-style boot processes, from which it derives. Although the Linux booting process depend very much on the computer architecture, those architectures share similar stages and software components, including system startup, bootloader execution, loading and startup of a Linux kernel image, and execution of various startup scripts and daemons. Those are grouped into 4 steps: system startup, bootloader stage, kernel stage, and init process. When a Linux system is powered up or reset, its processor will execute a specific firmware/program for system initialization, such as Power-on self-test, invoking the reset vector to start a program at a known address in flash/ROM, then load the bootloader into RAM for later execution. In personal computer (PC), not only limited to Linux-distro PC, this firmware/program is called BIOS, which is stored in the mainboard. In embedded Linux system, this firmware/program is called boot ROM. After being loaded into RAM, bootloader will execute to load the second-stage bootloader. The second-stage bootloader will load the kernel image into memory, decompress and initialize it then pass control to this kernel image. Second-stage bootloader also performs several operation on the system such as system hardware check, mounting the root device, loading the necessary kernel modules,... Finally, the very first user-space process starts, and other high-level system initializations are performed.
The Nexus One is an Android smartphone designed and manufactured by HTC as Google's first Nexus smartphone. The Nexus became available on January 5, 2010, and features the ability to transcribe voice to text, an additional microphone for dynamic noise suppression, and voice guided turn-by-turn navigation to drivers.
The Android Dev Phone (ADP) is a SIM-unlocked and bootloader unlocked Android device that is designed for advanced developers. While developers can use regular consumer devices purchased at retail to test and use their apps, some developers may choose not to use a retail device, preferring an unlocked or no-contract device.
Rooting is the process by which users of Android devices can attain privileged control over various subsystems of the device, usually smartphones. Because Android is based on a modified version of the Linux kernel, rooting an Android device gives similar access to administrative (superuser) permissions as on Linux or any other Unix-like operating system such as FreeBSD or macOS.
The hacking of consumer electronics is an increasingly common practice that users perform to customize and modify their devices beyond what is typically possible. This activity has a long history, dating from the days of early computer, programming, and electronics hobbyists.
The Android Debug Bridge is a programming tool used for the debugging of Android-based devices. The daemon on the Android device connects with the server on the host PC over USB or TCP, which connects to the client that is used by the end-user over TCP. Made available as open-source software under the Apache License by Google since 2007, features include a shell and the possibility to make backups. The adb software is available for Windows, Linux and macOS. It has been misused by botnets and other malware, for which mitigations were developed such as RSA authentication and device whitelisting.
Android software development is the process by which applications are created for devices running the Android operating system. Google states that "Android apps can be written using Kotlin, Java, and C++ languages" using the Android software development kit (SDK), while using other languages is also possible. All non-Java virtual machine (JVM) languages, such as Go, JavaScript, C, C++ or assembly, need the help of JVM language code, that may be supplied by tools, likely with restricted API support. Some programming languages and tools allow cross-platform app support. Third party tools, development environments, and language support have also continued to evolve and expand since the initial SDK was released in 2008. The official Android app distribution mechanism to end users is Google Play; it also allows staged gradual app release, as well as distribution of pre-release app versions to testers.
Team Win Recovery Project (TWRP), pronounced "twerp", is an open-source software custom recovery image for Android-based devices. It provides a touchscreen-enabled interface that allows users to install third-party firmware and back up the current system, functions usually not supported by stock recovery images. It is, therefore, often installed when flashing, installing, or rooting Android devices, although it does not require a device to be rooted before installation.
Odin is a utility software program developed and used by Samsung internally which is used to communicate with Samsung devices in Odin mode. It can be used to flash a custom recovery firmware image to a Samsung Android device. Odin is also used for unbricking certain Android devices. Odin is the Samsung proprietary alternative to Fastboot.
Custom firmware, also known as aftermarket firmware, is an unofficial new or modified version of firmware created by third parties on devices such as video game consoles, mobile phones, and various embedded device types to provide new features or to unlock hidden functionality. In the video game console community, the term is often written as custom firmware or simply CFW, referring to an altered version of the original system software inside a video game console such as the PlayStation Portable, PlayStation 3, PlayStation Vita/PlayStation TV, PlayStation 4, Nintendo 3DS and Nintendo Switch. Installing custom firmware on some devices requires bootloader unlocking.
Bootloader unlocking is the process of disabling the bootloader security that makes secure boot possible. It can make advanced customizations possible, such as installing a custom firmware. On smartphones this can be a custom Android distribution or another mobile operating system. Some bootloaders are not locked at all, others can be unlocked using a standard command, others need assistance from the manufacturer. Some do not include an unlocking method and can only be unlocked through a software exploit.
The Qualcomm Emergency Download mode, commonly known as Qualcomm EDL mode and officially known as Qualcomm HS-USB QD-Loader 9008 is a feature implemented in the boot ROM of a system on a chip by Qualcomm which can be used to recover bricked smartphones. On Google's Pixel 3, the feature was accidentally shown to users after the phone was bricked.
The Android recovery mode is a mode of Android used for installing updates and wipe data. It consists of a Linux kernel with ramdisk on a separate partition from the main Android system.
The booting process of Android devices starts at the power-on of the SoC and ends at the visibility of the home screen, or special modes like recovery and fastboot. The boot process of devices that run Android is influenced by the firmware design of the SoC manufacturers.
The Linux kernel can run on a variety of devices made by Apple, including devices where the unlocking of the bootloader is not possible with an official procedure, such as iPhones and iPads.
