GNU GRUB (short for GNU GRand Unified Bootloader, commonly referred to as GRUB) is a

boot loader 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 o ...

package from the

GNU Project The GNU Project ( ) is a free software, mass collaboration project announced by Richard Stallman on September 27, 1983. Its goal is to give computer users freedom and control in their use of their computers and Computer hardware, computing dev ...

. GRUB is the

reference implementation In the software development process, a reference implementation (or, less frequently, sample implementation or model implementation) is a program that implements all requirements from a corresponding specification. The reference implementation ...

of the

Free Software Foundation The Free Software Foundation (FSF) is a 501(c)(3) non-profit organization founded by Richard Stallman on October 4, 1985. The organisation supports the free software movement, with the organization's preference for software being distributed ...

Multiboot Specification The Multiboot specification is an open standard describing how a boot loader can load an x86 operating system kernel. The specification allows any compliant boot-loader implementation to boot any compliant operating-system kernel. Thus, it all ...

, which provides a user the choice to boot one of multiple

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

s installed on a computer set up for

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 ma ...

or select a specific

kernel Kernel may refer to: Computing * Kernel (operating system), the central component of most operating systems * Kernel (image processing), a matrix used for image convolution * Compute kernel, in GPGPU programming * Kernel method, in machine learnin ...

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 A Grand Unified Theory (GUT) is any Mathematical model, model in particle physics that merges the electromagnetism, electromagnetic, weak interaction, weak, and strong interaction, strong fundamental interaction, forces (the three gauge theory, ...

). It is predominantly used for

Unix-like A Unix-like (sometimes referred to as UN*X, *nix or *NIX) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Uni ...

systems.

Operation

GNU GRUB on MBR partitioned hard disk drives

Booting

When a computer is turned on, its

BIOS In computing, BIOS (, ; Basic Input/Output System, also known as the System BIOS, ROM BIOS, BIOS ROM or PC BIOS) is a type of firmware used to provide runtime services for operating systems and programs and to perform hardware initialization d ...

finds the primary bootable device (usually the computer's hard disk) and runs the initial bootstrap program from the

master boot record A master boot record (MBR) is a type of boot sector in the first block of disk partitioning, partitioned computer mass storage devices like fixed disks or removable drives intended for use with IBM PC-compatible systems and beyond. The concept ...

(MBR). The MBR is the first

sector Sector may refer to: Places * Sector, West Virginia, U.S. Geometry * Circular sector, the portion of a disc enclosed by two radii and a circular arc * Hyperbolic sector, a region enclosed by two radii and a hyperbolic arc * Spherical sector, a po ...

of the hard disk. This bootstrap program must be small because it has to fit in a single sector. For a long time, the size of a sector has been 512 bytes. Since 2009 there are hard disks available with a sector size of 4096 bytes, called

Advanced Format Advanced Format (AF) is any disk sector format used to store data in HDDs, SSDs and SSHDs that exceeds 528 bytes per sector, frequently 4096, 4112, 4160, or 4224-byte sectors. Larger sectors of an Advanced Format Drive (AFD) enable the integratio ...

disks, but , such hard disks are still accessed in 512-byte sectors, using the 512e emulation. The legacy MBR partition table supports a maximum of four partitions and occupies 64 bytes, combined. Together with the optional disk signature (four bytes) and disk timestamp (six bytes), this leaves between 434 and 446 bytes available for the

machine code In computer programming, machine code is computer code consisting of machine language instructions, which are used to control a computer's central processing unit (CPU). For conventional binary computers, machine code is the binaryOn nonb ...

of a boot loader. Although such a small space can be sufficient for very simple boot loaders, it is not big enough to contain a boot loader supporting complex and multiple file systems, menu-driven selection of boot choices, etc. Boot loaders with bigger footprints are therefore split into pieces, where the smallest piece fits in the MBR, while one or more larger pieces are stored in other locations such as empty sectors between the MBR and the first partition. The code in the MBR then does little more than starting the second part. The purpose of the remaining part(s) of the boot loader is to actually boot an operating system by configuring it and starting the

. Kernels are in most cases stored as files residing on appropriate file systems, but the concept of a file system is unknown to the BIOS. Thus, in BIOS-based systems, the duty of a boot loader is to access the content of those files, so it can be loaded into the

RAM Ram, ram, or RAM most commonly refers to: * A male sheep * Random-access memory, computer memory * Ram Trucks, US, since 2009 ** List of vehicles named Dodge Ram, trucks and vans ** Ram Pickup, produced by Ram Trucks Ram, ram, or RAM may also ref ...

and executed. One possible approach for boot loaders is to load kernel images by directly accessing hard disk sectors without understanding the underlying file system. Usually, an additional level of

indirection In computer programming, an indirection (also called a reference) is a way of referring to something using a name, reference, or container instead of the value itself. The most common form of indirection is the act of manipulating a value through ...

is required, in form of ''maps'' or ''map files'' auxiliary files that contain a list of physical sectors occupied by kernel images. Such maps need to be updated each time a kernel image changes its physical location on disk, due to installing new kernel images, file system defragmentation, etc. Also, in case of the maps changing their physical location, their locations need to be updated within the boot loader's MBR code, so the sectors indirection mechanism continues to work. This is not only cumbersome, but it also leaves the system in need of manual repairs in case something goes wrong during system updates. Another approach is to make a boot loader aware of the underlying file systems, so kernel images are configured and accessed using their actual

file path A path (or filepath, file path, pathname, or similar) is a text string that uniquely specifies an item in a hierarchical file system. Generally, a path is composed of directory names, special directory specifiers and optionally a filename, sepa ...

s. That requires a boot loader to contain a driver for each of the supported file systems, so they can be understood and accessed by the boot loader itself. This approach eliminates the need for hardcoded locations of hard disk sectors and existence of map files, and does not require MBR updates after kernel images are added or moved around. The configuration of a boot loader is stored in a regular file, which is also accessed in a file system-aware way to obtain boot configurations before the actual booting of any kernel images. Thus, fewer things can go wrong during system updates. As a downside, such boot loaders are larger and more complex. GNU GRUB uses the second approach, by understanding the underlying file systems. The boot loader itself is split into multiple ''stages'' so that it fits in the MBR boot scheme. Two major versions of GRUB are in common use: GRUB version 0, called ''GRUB legacy,'' is only prevalent in older releases of Linux distributions. ''GRUB 2'' was written from scratch and intended to replace its predecessor, and is now used by a majority of Linux distributions.

Version 0 (GRUB Legacy)

GRUB 0.x follows a two-stage approach. The master boot record (MBR) usually contains GRUB ''stage 1,'' or can contain a standard MBR implementation which chainloads GRUB ''stage 1'' from the active partition's boot sector. Given the small size of a boot sector (512 bytes), ''stage 1'' can do little more than load the next stage of GRUB by loading a few disk sectors from a fixed location near the start of the disk (within its first 1024 cylinders). ''Stage 1'' can load ''stage 2'' directly, but it is normally set up to load the ''stage 1.5.'', located in the first 30

KiB The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable un ...

of hard disk immediately following the MBR and before the first partition. In case this space is not available (unusual partition table, special disk drivers, GPT or LVM disk) the install of ''stage 1.5'' will fail. The ''stage 1.5'' image contains file system drivers, enabling it to directly load ''stage 2'' from any known location in the filesystem, for example from /boot/grub. ''Stage 2'' will then load the default configuration file and any other modules needed.

Version 2 (GRUB 2)

Startup on systems using
BIOS In computing, BIOS (, ; Basic Input/Output System, also known as the System BIOS, ROM BIOS, BIOS ROM or PC BIOS) is a type of firmware used to provide runtime services for operating systems and programs and to perform hardware initialization d ...
firmware

* See illustration in last image on the right. * boot.img (stage 1) is written to the first 440 bytes of the

Master Boot Record A master boot record (MBR) is a type of boot sector in the first block of disk partitioning, partitioned computer mass storage devices like fixed disks or removable drives intended for use with IBM PC-compatible systems and beyond. The concept ...

(MBR boot code in sector 0), or optionally in a partition boot sector (PBR). It addresses diskboot.img by a 64-bit LBA address. The actual sector number is written by grub-install. diskboot.img is the first sector of core.img with the sole purpose to load the rest of core.img identified by LBA sector numbers also written by grub-install. ** On MBR partitioned disks, core.img (stage 1.5) is stored in the empty sectors (if available) between the MBR and the first partition. Recent operating systems suggest a 1 MiB gap here for alignment (2047 512-byte, or 255 4KiB, sectors). This gap used to be 62 sectors (31 KiB) as a reminder of the sector number limit of

Cylinder-Head-Sector Cylinder-head-sector (CHS) is an early method for giving addresses to each physical block of data on a hard disk drive. It is a 3D-coordinate system made out of a vertical coordinate ''head'', a horizontal (or radial) coordinate ''cylinder'', an ...

(C/H/S) addressing used by

before 1996, therefore core.img is designed to be smaller than 32 KiB. **On GPT partitioned disks core.img is written to its own partition. It must be flagged "BIOS_grub", must not be formatted and can be as tiny as 1 MiB. * stage 2: core.img loads /boot/grub/i386-pc/normal.mod from the partition configured by grub-install. If the partition index has changed, GRUB will be unable to find the normal.mod, and presents the user with the GRUB Rescue prompt. * Depending on how GRUB2 was installed, the /boot/grub/ is either in the ''root'' partition of the Linux distribution, or in the separate ''/boot'' partition. * after normal.mod loaded: normal.mod parses /boot/grub/grub.cfg, optionally loads modules (eg. for graphical UI and file system support) and shows the menu.

Startup on systems using
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 ...
firmware

* /efi//grubx64.efi (for

x64 x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit extension of the x86 instruction set. It was announced in 1999 and first available in the AMD Opteron family in 2003. It introduces two new operating modes: 64-bit mode an ...

UEFI systems) is installed as a file in the EFI System Partition, and booted by the firmware directly, without a boot.img in MBR sector 0. This file is like stage1 and stage1.5. * /boot/grub/ can be installed on the EFI System Partition or the separate ''/boot'' partition, among others. * For x64 UEFI systems, stage2 are the /boot/grub/x86_64-efi/normal.mod file and other /boot/grub/ files.

After startup

GRUB presents a menu where the user can choose from operating systems (OS) found by grub-install. GRUB can be configured to automatically load a specified OS after a user-defined timeout. If the timeout is set to zero seconds, pressing and holding , or in some modern GRUB versions loaded using UEFI, pressing rapidly while the computer is booting makes it possible to access the boot menu. In the operating system selection menu GRUB accepts a couple of commands: * By pressing , it is possible to edit kernel parameters of the selected menu item ''before the operating system is started''. The reason for doing this in GRUB (i.e. not editing the parameters in an already booted system) can be an emergency case: the system has failed to boot. Using the kernel parameters line it is possible, among other things, to specify a module to be disabled (blacklisted) for the kernel. This could be required if the specific kernel module is broken and thus prevents boot-up. For example, to blacklist the kernel module nvidia-current, one could append modprobe.blacklist=nvidia-current at the end of the kernel parameters. * By pressing , the user enters the GRUB command line. The GRUB command line resembles GNU Bash, but only implements a subset of the line editing functions and GRUB-specific commands. Once boot options have been selected, GRUB loads the selected kernel into memory and passes control to the kernel. Alternatively, GRUB can pass control of the boot process to another boot loader, using ''

chain loading Chain loading is a method used by computer programs to replace the currently executing program with a new program, using a common data area to pass information from the current program to the new program. It occurs in several areas of computing. ...

''. This is the method used to load operating systems that do not support the

or are not supported directly by GRUB.

Identifying partitions (UUID workaround)

A computer can have multiple hard disks connected to it. These could be identified via their SATA port. Each time the computer POSTs, the hard disk connected to a specific motherboard port ''could'' be assigned the same identifier, for example . But what if such consistency cannot be guaranteed? What if the constellation of connected hard disks changed from one start up to another? What if a hard disk will be connected to another computer? By entering into either the ''GRUB rescue console'' (available after loading core.img ) or the ''GRUB console'' (available after loading normal.mod) a list of all available hard disks and partitions can be obtained. For example, ) will show numbers that can be assigned to actual hard disks and partitions. As it cannot be guaranteed that the "hd0"style numbering of hard disks via device numbers is consistent, GNU GRUB can use a

Universally Unique Identifier A Universally Unique Identifier (UUID) is a 128-bit label used to uniquely identify objects in computer systems. The term Globally Unique Identifier (GUID) is also used, mostly in Microsoft systems. When generated according to the standard methods ...

(UUID) to identify partitions (actually file system instances). The file systems ext2, ext3, ext4 and xfs use a UUID to uniquely identify an instance. The UUID is created when a partition is formatted. The UUID is part of the file system and written to the superblock. All operations other than formatting should leave the UUID unaltered. It is possible to change the UUID or duplicate it by using dd to clone an entire partition. The file is used to configure GRUB. It contains commands to be executed during each start-up. Without an existing and valid , GRUB will present a prompt. An absolute minimal might contain only the following two commands (cf.

initial ramdisk In Linux systems, initrd (''initial ramdisk'') is a scheme for loading a temporary root file system into computer memory, memory, to be used as part of the Linux startup process. initrd and initramfs (from INITial RAM File System) refer to two dif ...

linux (hd0,1)/kernel/vmlinuz-3.20.1-4 ro  # use the file name "vmlinuz-…" located in the directory /kernel on the first partition of the first hard disk as linux kernel image
initrd (hd0,1)/boot/initrd.img-3.20.1-4   # use the file named "initrd.img–…" located in the directory /boot on the first partition of the first hard disk as initial ramdisk

A fancier will describe a menu to be presented, use multiple colors, and may specify a background picture.

History

GRUB was initially developed by Erich Boleyn as part of work on booting the

GNU GNU ( ) is an extensive collection of free software (394 packages ), which can be used as an operating system or can be used in parts with other operating systems. The use of the completed GNU tools led to the family of operating systems popu ...

Hurd GNU Hurd is a collection of microkernel servers written as part of GNU, for the GNU Mach microkernel. It has been under development since 1990 by the GNU Project of the Free Software Foundation, designed as a replacement for the Unix kernel, and ...

, developed by the

.GRUB Manual – 1.2 Grub History
. Gnu.org (2012-06-23). Retrieved on 2012-12-01. In 1999, Gordon Matzigkeit and Yoshinori K. Okuji made GRUB an official software package of the

and opened the development process to the public. , the majority of Linux distributions have adopted GNU GRUB 2.

Development

GRUB version 0 (also known as "GRUB Legacy") is no longer under development and is being phased out. The GNU GRUB developers have switched their focus to GRUB 2, a complete rewrite with goals including making GNU GRUB cleaner, more robust, more portable and more powerful. GRUB 2 started under the name PUPA. PUPA was supported by the Information-technology Promotion Agency (IPA) in Japan. PUPA was integrated into GRUB 2 development around 2002, when GRUB version 0.9x was renamed GRUB Legacy. Some of the goals of the GRUB 2 project include support for non-x86 platforms,

internationalization and localization In computing, internationalization and localization (American English, American) or internationalisation and localisation (British English, British), often abbreviated i18n and l10n respectively, are means of adapting to different languages, regi ...

, non-ASCII characters, dynamic modules,

memory management Memory management (also dynamic memory management, dynamic storage allocation, or dynamic memory allocation) is a form of Resource management (computing), resource management applied to computer memory. The essential requirement of memory manag ...

, a scripting

mini-language A domain-specific language (DSL) is a computer language specialized to a particular application domain. This is in contrast to a general-purpose language (GPL), which is broadly applicable across domains. There are a wide variety of DSLs, ranging ...

, migrating platform specific (x86) code to platform specific modules, and an object-oriented framework. GNU GRUB version 2.00 was officially released on June 26, 2012. Three of the most widely used

Linux distribution A Linux distribution, often abbreviated as distro, is an operating system that includes the Linux kernel for its kernel functionality. Although the name does not imply product distribution per se, a distro—if distributed on its own—is oft ...

s use GRUB 2 as their mainstream boot loader.

Ubuntu Ubuntu ( ) is a Linux distribution based on Debian and composed primarily of free and open-source software. Developed by the British company Canonical (company), Canonical and a community of contributors under a Meritocracy, meritocratic gover ...

adopted it as the default boot loader in its 9.10 version of October 2009.

Fedora A fedora () is a hat with a soft brim and indented crown.Kilgour, Ruth Edwards (1958). ''A Pageant of Hats Ancient and Modern''. R. M. McBride Company. It is typically creased lengthwise down the crown and "pinched" near the front on both sides ...

followed suit with Fedora 16 released in November 2011.

OpenSUSE openSUSE () is a free and open-source software, free and open-source Linux distribution developed by the openSUSE project. It is offered in two main variations: ''Tumbleweed'', an upstream rolling release distribution, and ''Leap'', a stable r ...

adopted GRUB 2 as the default boot loader with its 12.2 release of September 2012.

Solaris Solaris is the Latin word for sun. It may refer to: Arts and entertainment Literature, television and film * ''Solaris'' (novel), a 1961 science fiction novel by Stanisław Lem ** ''Solaris'' (1968 film), directed by Boris Nirenburg ** ''Sol ...

also adopted GRUB 2 on the x86 platform in the Solaris 11.1 release.

Buildroot Buildroot is a set of Makefiles and Patch (Unix), patches that simplifies and automates the process of building a complete and bootable Linux environment for an embedded system, while using Cross compiler, cross-compilation to allow building for ...

also uses GNU GRUB for

x86 x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel, based on the 8086 microprocessor and its 8-bit-external-bus variant, the 8088. Th ...

and

x86_64 x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit extension of the x86 instruction set. It was announced in 1999 and first available in the AMD Opteron family in 2003. It introduces two new operating modes: 64-bit mode a ...

targets. In late 2015, the exploit of pressing backspace 28 times to bypass the login password was found and quickly fixed.

Variants

GNU GRUB is

free software Free software, libre software, libreware sometimes known as freedom-respecting software is computer software distributed open-source license, under terms that allow users to run the software for any purpose as well as to study, change, distribut ...

, so several variants have been created. Some notable ones, which have not been merged into GRUB mainline: *

OpenSolaris OpenSolaris () is a discontinued open-source computer operating system for SPARC and x86 based systems, created by Sun Microsystems and based on Solaris. Its development began in the mid 2000s and ended in 2010. OpenSolaris was developed as ...

includes a modified GRUB Legacy that supports Solaris VTOC slices, automatic 64-bit kernel selection, and booting from

ZFS ZFS (previously Zettabyte File System) is a file system with Volume manager, volume management capabilities. It began as part of the Sun Microsystems Solaris (operating system), Solaris operating system in 2001. Large parts of Solaris, includin ...

(with

compression Compression may refer to: Physical science *Compression (physics), size reduction due to forces *Compression member, a structural element such as a column *Compressibility, susceptibility to compression * Gas compression *Compression ratio, of a ...

and multiple boot environments). *

Google Summer of Code The Google Summer of Code, often abbreviated to GSoC, is an international annual program in which Google awards stipends to contributors who successfully complete a free and open-source software coding project during the summer. , the program is ...

2008 had a project to support GRUB legacy to boot from

ext4 ext4 (fourth extended filesystem) is a journaling file system for Linux, developed as the successor to ext3. ext4 was initially a series of backward-compatible extensions to ext3, many of them originally developed by Cluster File Systems for ...

formatted partitions. * The

Syllable A syllable is a basic unit of organization within a sequence of speech sounds, such as within a word, typically defined by linguists as a ''nucleus'' (most often a vowel) with optional sounds before or after that nucleus (''margins'', which are ...

project made a modified version of GRUB to load the system from its

AtheOS File System Syllable Desktop is a discontinued free and open-source lightweight hobbyist operating system for Pentium and compatible processors. Its purpose was to create an easy-to-use desktop operating system for the home and small office user. Its develop ...

. * ''TrustedGRUB'' extends GRUB by implementing verification of the system integrity and boot process security, using the

Trusted Platform Module A Trusted Platform Module (TPM) is a secure cryptoprocessor that implements the ISO/IEC 11889 standard. Common uses are verifying that the boot process starts from a trusted combination of hardware and software and storing disk encryption keys. ...

(TPM). * The Intel BIOS Implementation Test Suite (BITS) provides a GRUB environment for testing BIOSes and in particular their initialization of Intel processors, hardware, and technologies. BITS supports scripting via Python, and includes Python APIs to access various low-level functionality of the hardware platform, including ACPI, CPU and chipset registers, PCI, and PCI Express. * GRUB4DOS is a GRUB legacy fork that improves the installation experience on DOS and

Microsoft Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

by putting everything besides the GRLDR config in one image file. It can be loaded directly from DOS, or by

NTLDR NTLDR (abbreviation of ''NT loader'') is the boot loader for all releases of Windows NT operating system from 1993 with the release of Windows NT 3.1 up until Windows XP and Windows Server 2003. From Windows Vista onwards it was replaced by the B ...

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 ...

. GRUB4DOS is under active development and as of 2021 supports UEFI.

Utilities

GRUB configuration tools

The setup tools in use by various distributions often include modules to set up GRUB. For example,

YaST2 YaST (Yet another Setup Tool) is a Linux operating system setup and configuration tool. YaST is featured in the openSUSE Linux distribution, as well as in SUSE's derived commercial distributions. It is also part of the defunct United Linux. Ya ...

SUSE Linux openSUSE () is a free and open-source Linux distribution developed by the openSUSE project. It is offered in two main variations: ''Tumbleweed'', an upstream rolling release distribution, and ''Leap'', a stable release distribution which is so ...

and

openSUSE openSUSE () is a free and open-source software, free and open-source Linux distribution developed by the openSUSE project. It is offered in two main variations: ''Tumbleweed'', an upstream rolling release distribution, and ''Leap'', a stable r ...

distributions and

Anaconda Anacondas or water boas are a group of large boas of the genus ''Eunectes''. They are a semiaquatic group of snakes found in tropical South America. Three to five extant and one extinct species are currently recognized, including one of the l ...

RHEL Red Hat Enterprise Linux (RHEL) is a commercial Linux distribution developed by Red Hat. Red Hat Enterprise Linux is released in server versions for x86-64, Power ISA, ARM64, and IBM Z and a desktop version for x86-64. Fedora Linux and CentOS St ...

distributions. StartUp-Manager and GRUB Customizer are graphical configuration editors for Debian-based distributions. The development of StartUp-Manager stopped on 6 May 2011 after the lead developer cited personal reasons for not actively developing the program. GRUB Customizer is also available for Arch-based distributions. For GRUB 2 there are KDE Control Modules. GRLDR ICE is a tiny tool for modifying the default configuration of grldr file for GRUB4DOS.

Boot repair utilities

Boot-Repair is a simple graphical tool for recovering from frequent boot-related problems with GRUB and

bootloader. This application is available under

GNU GPL license The GNU General Public Licenses (GNU GPL or simply GPL) are a series of widely used free software licenses, or ''copyleft'' licenses, that guarantee end users the freedom to run, study, share, or modify the software. The GPL was the first c ...

. Boot-Repair can repair GRUB on multiple Linux distributions including, but not limited to, Debian, Ubuntu,

Mint Mint or The Mint may refer to: Plants * Lamiaceae, the mint family ** ''Mentha'', the genus of plants commonly known as "mint" Coins and collectibles * Mint (facility), a facility for manufacturing coins * Mint condition, a state of like-new ...

, Fedora, openSUSE, and

Arch Linux Arch Linux () is an Open-source software, open source, rolling release Linux distribution. Arch Linux is kept up-to-date by regularly updating the individual pieces of software that it comprises. Arch Linux is intentionally minimal, and is meant ...

Installer for Windows

Grub2Win is a Windows open-source software package. It allows GNU GRUB to boot from a Windows directory. The setup program installs GNU GRUB version 2.12 to an NTFS partition. A Windows GUI application is then used to customize the GRUB boot menu, themes, UEFI boot order, scripts etc. All GNU GRUB scripts and commands are supported for both UEFI and legacy systems. Grub2Win can configure GRUB for multiboot of Windows, Ubuntu, openSuse, Fedora and many other Linux distributions. It is freely available under

GNU GPL License The GNU General Public Licenses (GNU GPL or simply GPL) are a series of widely used free software licenses, or ''copyleft'' licenses, that guarantee end users the freedom to run, study, share, or modify the software. The GPL was the first c ...

SourceForge SourceForge is a web service founded by Geoffrey B. Jeffery, Tim Perdue, and Drew Streib in November 1999. SourceForge provides a centralized software discovery platform, including an online platform for managing and hosting open-source soft ...

Alternative boot managers

The strength of GRUB is the wide range of supported platforms, file systems, and operating systems, making it the default choice for distributions and embedded systems. However, there are boot managers targeted at the end user that give more friendly user experience, graphical OS selector and simpler configuration: *

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 ...

– Macintosh-style graphical boot manager, only for UEFI-based computers (BIOS not supported).
CloverEFI
– Macintosh-style graphical boot manager for BIOS and UEFI-based computers. It emulates UEFI with a heavily modifie
DUET
from the TianoCore project and requires a FAT formatted partition even on BIOS systems. As a benefit, it has a basic filesystem driver in the partition boot sector, avoiding the brittleness of a second or third stage and the infamous GRUB Rescue prompt. The user interface looks similar to rEFInd: both inherit from the abandoned boot manage
rEFIt
Non-graphical alternatives: * systemd-boot – Light, UEFI-only boot manager with text-based OS selector menu.

External links

How-Tos and troubleshooting

Distribution wikis have many solutions for common issues and custom setups that might help you:
Arch Linux /GRUB

Ubuntu /Grub2
(also see Links at the bottom) * Fedora /GRUB_2 * Gentoo /GRUB2
Grub2 theme tutorial

Documentation

GRUB manual
– most detailed documentation, including all commands *
GRUB wiki archived in 2010

Introductory articles

Boot with GRUB
an April 2001 article in

Linux Journal ''Linux Journal'' (''LJ'') is an American monthly technology magazine originally published by Specialized System Consultants, Inc. (SSC) in Seattle, Washington since 1994. In December 2006 the publisher changed to Belltown Media, Inc. in Hous ...

Technicalities

Booting Linux on x86 using Grub2
– in-depth article *

Unified Extensible Firmware Interface 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 ...

(UEFI firmware, common since 2012) *

GUID Partition Table The GUID Partition Table (GPT) is a standard for the layout of partition tables of a physical computer storage device, such as a hard disk drive or solid-state drive. It is part of the Unified Extensible Firmware Interface (UEFI) standard. It ha ...

(GPT) – handles hard drives bigger than 2 TiB and more than 4 partitions *

Master boot record A master boot record (MBR) is a type of boot sector in the first block of disk partitioning, partitioned computer mass storage devices like fixed disks or removable drives intended for use with IBM PC-compatible systems and beyond. The concept ...

used with BIOS firmware (motherboards roughly before 2012)
BIOS Boot Specification Version 1.01 (January 11, 1996)
– hard to find

Notes

References

{{Firmware and booting, state=collapsed Free boot loaders Free software primarily written in assembly language Free software programmed in C

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 use ...

Research projects 1995 software