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A boot disk is a removable digital data storage medium from which a computer can load and run ( boot) an
operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...
or utility program. The computer must have a built-in program which will load and execute a program from a boot disk meeting certain standards. While almost all modern computers can boot from a hard drive containing the operating system and other software, they would not normally be called boot disks (because they are not removable media). CD-ROMs are the most common forms of media used, but other media, such as magnetic or paper tape drives,
ZIP drive The Zip drive is a removable floppy disk storage system that was introduced by Iomega in late 1994. Considered medium-to-high-capacity at the time of its release, Zip disks were originally launched with capacities of 100  MB, then 250 ...
s, and more recently
USB flash drive Universal Serial Bus (USB) is an industry standard that establishes specifications for cables, connectors and protocols for connection, communication and power supply ( interfacing) between computers, peripherals and other computers. A bro ...
s can be used. The computer's BIOS must support booting from the device in question. One can make one's own ''boot disk'' (typically done to prepare for when the system won't start properly).


Uses

Boot disks are used for: *
Operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...
installation *
Data recovery In computing, data recovery is a process of retrieving deleted, inaccessible, lost, corrupted, damaged, or formatted data from secondary storage, removable media or files, when the data stored in them cannot be accessed in a usual way. The dat ...
* Data purging * Hardware or software troubleshooting * BIOS flashing * Customizing an operating environment * Software demonstration * Running a temporary operating environment, such as when using a
Live USB 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, th ...
drive. * Administrative access in case of lost password is possible with an appropriate boot disk with some operating systems * Games (e.g. for Amiga home computers, running
MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few ope ...
video games on modern computers by using a bootable
MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few ope ...
or
FreeDOS FreeDOS (formerly Free-DOS and PD-DOS) is a free software operating system for IBM PC compatible computers. It intends to provide a complete MS-DOS-compatible environment for running legacy software and supporting embedded systems. FreeDOS can ...
USB flash drive).


Process

The term ''boot'' comes from the idea of lifting oneself by one's own bootstraps: the computer contains a tiny program (bootstrap loader) which will load and run a program found on a boot device. This program may itself be a small program designed to load a larger and more capable program, i.e., the full operating system. To enable booting without the requirement either for a
mass storage In computing, mass storage refers to the storage of large amounts of data in a persisting and machine-readable fashion. In general, the term is used as large in relation to contemporaneous hard disk drives, but it has been used large in relati ...
device or to write to the boot medium, it is usual for the boot program to use some system
RAM Ram, ram, or RAM may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch * ...
as a
RAM disk Ram, ram, or RAM may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch * ...
for temporary
file File or filing may refer to: Mechanical tools and processes * File (tool), a tool used to ''remove'' fine amounts of material from a workpiece **Filing (metalworking), a material removal process in manufacturing ** Nail file, a tool used to gent ...
storage. As an example, any computer compatible with the IBM PC is able with built-in software to load the contents of the first 512 bytes of a floppy and to execute it if it is a viable program; boot floppies have a very simple loader program in these bytes. The process is vulnerable to abuse; data floppies could have a virus written to their first sector which silently infects the host computer if switched on with the disk in the drive.


Media

Bootable floppy disks ("boot floppies") for PCs usually contain
DOS DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems. DOS may also refer to: Computing * Data over signalling (DoS), multiplexing data onto a signalling channel * Denial-of-service attack (DoS), an attack on a communicat ...
or miniature versions of
Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, w ...
. The most commonly available floppy disk can hold only 1.4 MB of data in its standard format, making it impractical for loading large
operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...
s. The use of boot floppies is in decline, due to the availability of other higher-capacity options, such as CD-ROMs or
USB flash drives A USB flash drive (also called a thumb drive) is a data storage device that includes flash memory with an integrated USB interface. It is typically removable, rewritable and much smaller than an optical disc. Most weigh less than . Since first ...
.


Device selection

A modern PC is configured to attempt to boot from various devices in a certain order. If a computer is not booting from the device desired, such as the floppy drive, the user may have to enter the BIOS Setup function by pressing a special key when the computer is first turned on (such as , , , or ), and then changing the boot order. More recent BIOSes permit the interruption of the final stage of the boot process and invoke the Boot Menu by pressing a function key (usually or ). This results in a list of bootable devices being presented, from which a selection may be made.
Apple silicon Apple silicon is a series of system on a chip (SoC) and system in a package (SiP) processors designed by Apple Inc., mainly using the ARM architecture. It is the basis of most new Mac computers as well as iPhone, iPad, iPod Touch, Apple TV, ...
Macs display the Boot Menu when the power button is pressed and held, the older
Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, where its wild ancestor, ' ...
Macintosh The Mac (known as Macintosh until 1999) is a family of personal computers designed and marketed by Apple Inc. Macs are known for their ease of use and minimalist designs, and are popular among students, creative professionals, and software en ...
computers with
Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 seri ...
processors will display the Boot Menu if user presses the or while the machine is starting.


Requirements

Different operating systems use different boot disk contents. All boot disks must be compatible with the computer they are designed for. ; MS-DOS/PC DOS/DR-DOS: *A valid boot sector in form of a volume boot record (VBR) *
IO.SYS is an essential part of MS-DOS and Windows 9x. It contains the default MS-DOS device drivers (hardware interfacing routines) and the DOS initialization program. Boot sequence In the PC bootup sequence, the first sector of the boot disk is ...
or IBMBIO.COM *
MSDOS.SYS MSDOS.SYS is a system file in MS-DOS and Windows 9x operating systems. In versions of MS-DOS from 1.1x through 6.22, the file comprises the MS-DOS kernel and is responsible for file access and program management. MSDOS.SYS is loaded by the DOS BI ...
or IBMDOS.COM *
COMMAND.COM COMMAND.COM is the default command-line interpreter for MS-DOS, Windows 95, Windows 98 and Windows Me. In the case of DOS, it is the default user interface as well. It has an additional role as the usual first program run after boot (init proc ...
All files must be for the same version of the operating system. Complete boot disks can be prepared in one operation by an installed operating system; details vary. ; FreeDOS: *A valid boot sector on the disk *COMMAND.COM *KERNEL.SYS ; Linux: *A bootloader such as SYSLINUX or
GRUB Grub can refer to Grub (larva), of the beetle superfamily Scarabaeoidea, or as a slang term for food. It can also refer to: Places * Grub, Appenzell Ausserrhoden, Switzerland * Grub, St. Gallen, Switzerland * Grub (Amerang), a hamlet in Bavar ...
* Linux kernel *Initial ram disk (
initrd In Linux systems, initrd (''initial ramdisk'') is a scheme for loading a temporary root file system into memory, to be used as part of the Linux startup process. initrd and initramfs refer to two different methods of achieving this. Both are comm ...
) ; Windows Preinstallation Environment: *
Windows Boot Manager The booting process of Windows Vista and later versions differ from the startup process part of previous versions of Windows. In this article, unless otherwise specified, what is said about Windows Vista also applies to all later NT operatin ...
*BOOT.WIM


See also

*
Darik's Boot and Nuke Darik's Boot and Nuke, also known as DBAN , is a free and open-source project hosted on SourceForge. The program is designed to securely erase a hard disk until its data is permanently removed and no longer recoverable, which is achieved by ...
*
Data recovery In computing, data recovery is a process of retrieving deleted, inaccessible, lost, corrupted, damaged, or formatted data from secondary storage, removable media or files, when the data stored in them cannot be accessed in a usual way. The dat ...
*
El Torito (CD-ROM standard) ISO 9660 (also known as ECMA-119) is a file system for optical disc media. Being sold by the International Organization for Standardization (ISO) the file system is considered an international technical standard. Since the specification is av ...
*
Live CD A live CD (also live DVD, live disc, or live operating system) is a complete bootable computer installation including operating system which runs directly from a CD-ROM or similar storage device into a computer's memory, rather than loading f ...
*
Protected Area Run Time Interface Extension Services The host protected area (HPA) is an area of a hard drive or solid-state drive that is not normally visible to an operating system. It was first introduced in the ATA-4 standard CXV (T13) in 2001. How it works The IDE controller has registers ...
(PARTIES) * Self-loader


References

{{reflist


External links


reboot.pro - Community forum dedicated to Boot Disks

Boot Disk information, sources, and tools
Bootable media