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Bootloaders
A bootloader, also spelled as boot loader or called bootstrap loader, is a computer program that is responsible for booting a computer and booting an operating system. If it also provides an interactive menu with multiple boot choices then it's often called a boot manager. When a computer is turned off, its softwareincluding operating systems, application code, and dataremains stored on non-volatile memory. When the computer is powered on, it typically does not have an operating system or its loader in random-access memory (RAM). The computer first executes a relatively small program stored in the boot ROM, which is read-only memory (ROM, and later EEPROM, Flash memory#NOR flash, NOR flash) along with some needed data, to initialize hardware devices such as CPU, motherboard, memory, storage and other I/O devices, to access the nonvolatile device (usually Device file#Block devices, block device, e.g., NAND flash) or devices from which the operating system programs and data can be l ...
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Das U-Boot
Das U-Boot (subtitled "the Universal Boot Loader" and often shortened to U-Boot; see ''#History, History'' for more about the name) is an open-source software, open-source Bootloader, boot loader used in Embedded system, 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 Motorola 68000 series, M68000, ARM architecture, ARM, Blackfin, MicroBlaze, AArch64, MIPS architecture, MIPS, Nios II, SuperH, PowerPC, PPC, Power ISA, RISC-V, LoongArch and x86 architecture, x86. Functionality U-Boot is both a first-stage and second-stage bootloader. It is loaded by the system's ROM (e.g. on-chip ROM of an ARM CPU) from a supported boot device, such as an SD card, SATA drive, NOR flash (e.g. using Serial Peripheral Interface Bus, SPI or I²C), or NAND flash. If there are size constraints, U-Boot may be split into two stages: the platform would load a small ...
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Boot ROM
Boot ROM is a piece of read-only memory (ROM) that is used for booting a computer system. It contains instructions that are run after the CPU is reset to the reset vector, and it typically loads a bootloader. There are two types of boot ROM: a mask boot ROM that cannot be changed afterwards, and a writable boot ROM such as an EEPROM or a flash memory chip. Purpose Upon power up, hardware usually starts uninitialized. To continue booting, the system may need to read a bootloader from some peripheral device. It is often easier to implement routines for reading from external storage devices in software than in hardware. A boot ROM provides a place to store this initial loading code, at a fixed location immediately available to the processor when execution starts. Operation The boot ROM is mapped into memory at a fixed location, and the processor is designed to start executing from this location after reset, according to the processor's reset vector. The boot ROM is eith ...
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UEFI
Unified Extensible Firmware Interface (UEFI, as an acronym) is a Specification (technical standard), specification for the firmware Software architecture, architecture of a computing platform. When a computer booting, is powered on, the UEFI implementation is typically the first that runs, before starting the operating system. Examples include AMI Aptio, Phoenix Technologies, Phoenix SecureCore, TianoCore EDK II, and InsydeH2O. UEFI replaces the BIOS that was present in the boot ROM of all personal computers that are IBM PC compatible, although it can provide Backward compatibility, backwards compatibility with the BIOS using #CSM booting, CSM booting. Unlike its predecessor, BIOS, which is a de facto standard originally created by IBM as proprietary software, UEFI is an open standard maintained by an industry consortium. Like BIOS, most UEFI implementations are proprietary. Intel developed the original ''Extensible Firmware Interface'' (''EFI'') specification. The last Inte ...
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GRUB V2
GNU GRUB (short for GNU GRand Unified Bootloader, commonly referred to as GRUB) is a boot loader package from the GNU Project. GRUB is the reference implementation of the Free Software Foundation's Multiboot Specification, which provides a user the choice to boot one of multiple operating systems installed on a computer set up for multi-booting or select a specific Kernel (operating system), kernel configuration available on a particular operating system's partitions. GNU GRUB was developed from a package called the ''Grand Unified Bootloader'' (a play on Grand Unified Theory). It is predominantly used for Unix-like systems. Operation Booting When a computer is turned on, its BIOS finds the primary bootable device (usually the computer's hard disk) and runs the initial Bootstrapping (computing), bootstrap program from the master boot record (MBR). The MBR is the first Disk sector, sector of the hard disk. This bootstrap program must be small because it has to fit in a sin ...
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Booting
In computing, booting is the process of starting a computer as initiated via Computer hardware, hardware such as a physical button on the computer or by a software command. After it is switched on, a computer's central processing unit (CPU) has no software in its main memory, so some process must load software into memory before it can be executed. This may be done by hardware or firmware in the CPU, or by a separate processor in the computer system. On some systems a power-on reset (POR) does not initiate booting and the operator must initiate booting after POR completes. IBM uses the term Initial Program Load (IPL) on someE.g., System/360 through IBM Z, RS/6000 and System/38 through IBM Power Systems product lines. Restarting a computer also is called Reboot (computing), ''rebooting'', which can be "hard", e.g. after electrical power to the CPU is switched from off to on, or "soft", where the power is not cut. On some systems, a soft boot may optionally clear RAM to zero. Bo ...
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GNU GRUB
GNU GRUB (short for GNU GRand Unified Bootloader, commonly referred to as GRUB) is a boot loader package from the GNU Project. GRUB is the reference implementation of the Free Software Foundation's Multiboot Specification, which provides a user the choice to boot one of multiple operating systems installed on a computer set up for multi-booting or select a specific Kernel (operating system), kernel configuration available on a particular operating system's partitions. GNU GRUB was developed from a package called the ''Grand Unified Bootloader'' (a play on Grand Unified Theory). It is predominantly used for Unix-like systems. Operation Booting When a computer is turned on, its BIOS finds the primary bootable device (usually the computer's hard disk) and runs the initial Bootstrapping (computing), bootstrap program from the master boot record (MBR). The MBR is the first Disk sector, sector of the hard disk. This bootstrap program must be small because it has to fit in a sin ...
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Multi-booting
Multi-booting is the act of installing multiple operating systems on a single computer, and being able to choose which one to boot. The term dual-booting refers to the common configuration of specifically two operating systems. Multi-booting may require a custom boot loader. Usage Multi-booting allows more than one operating system to reside on one computer; for example, if a user has a primary operating system that they use most frequently and an alternate operating system that they use less frequently. Multi-booting allows a new operating system to configure all applications needed and migrate data before removing the old operating system, if desired. Another reason for multi-booting can be to investigate or test a new operating system without switching completely. Multi-booting is also useful in situations where different software requires different operating systems. A multi-boot configuration allows a user to use all of their software on one computer. This is often accompl ...
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Windows Boot Manager
The Windows Boot Manager (BOOTMGR) is the bootloader provided by Microsoft for Windows NT versions starting with Windows Vista and Windows Server 2008. It is the first program launched by the BIOS or UEFI of the computer and is responsible for loading the rest of Windows. It replaced the NTLDR present in older versions of Windows. The boot sector or UEFI loads the Windows Boot Manager (a file named BOOTMGR on either the system or the boot partition), accesses the Boot Configuration Data store and uses the information to load the operating system through winload.exe or winresume.exe on BIOS systems, and winload.efi and winresume.efi on UEFI systems. Launching On system with BIOS firmware, the BIOS invokes MBR boot code from a hard disk drive at startup. The MBR boot code and the VBR boot code are OS-specific. In Microsoft Windows, the MBR boot code tries to find an active partition (the MBR is only 512 bytes), then executes the VBR boot code of an active partition. The VB ...
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Libreboot
Libreboot (briefly known as GNU Libreboot) is a free and open-source software project based on coreboot, aimed at replacing some of the proprietary BIOS or UEFI firmware on supported x86-64 and AArch64 computers. Libreboot performs the basic machine setup such as CPU initialization or memory controller initialization necessary to load and run a 32-bit or 64-bit operating system, such as Linux or FreeBSD. Characteristics Libreboot is established as a distribution of coreboot, but with some proprietary binary blobs removed from coreboot. Libreboot makes coreboot easy to use by automating the build and installation processes. On some devices, Libreboot developers have reverse engineered the firmware from Intel and created a utility to create a free firmware that meets the specifications from Intel. Hardware support includes but is not limited to the ASUS KGPE-D16, ThinkPad T400, X60 and X200. Libreboot is officially endorsed by the upstream coreboot project. Hist ...
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REFInd
rEFInd is a boot manager for UEFI and EFI-based machines. It can be used to boot multiple operating systems that are installed on a single non-volatile device. It also provides a way to launch UEFI applications. It was forked from discontinued rEFIt in 2012, with 0.2.0 as its first release. rEFind supports the IA-32, x86-64, and AArch64 architectures. Features rEFInd has several features: * Automatic operating systems detection. * Customisable OS launch options. * Graphical or text mode. Theme is customisable. * Mac-specific features, including spoofing booting process to enable secondary video chipsets on some Mac. * Linux-specific features, including autodetecting EFI stub loader to boot Linux kernel directly and using fstab in lieu of rEFInd configuration file for boot order. * Support for Secure Boot. Adoption rEFInd is the default UEFI boot manager for TrueOS. rEFInd is included in official repositories of major Linux distributions. Development GNU-EFI and ...
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Device Driver
In the context of an operating system, a device driver is a computer program that operates or controls a particular type of device that is attached to a computer or automaton. A driver provides a software interface to hardware devices, enabling operating systems and other computer programs to access hardware functions without needing to know precise details about the hardware being used. A driver communicates with the device through the computer bus or communications subsystem to which the hardware connects. When a calling program invokes a routine in the driver, the driver issues commands to the device (drives it). Once the device sends data back to the driver, the driver may invoke routines in the original calling program. Drivers are hardware dependent and operating-system-specific. They usually provide the interrupt handling required for any necessary asynchronous time-dependent hardware interface. Purpose The main purpose of device drivers is to provide abstraction b ...
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