Boot disk

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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 or utility program. [1] The computer must have a built-in program which will load and execute a program from a boot disk meeting certain standards.

Contents

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 drives, and more recently USB flash drives 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). [2]

Uses

Boot disks are used for:

Process

The term boot comes from the idea of lifting oneself by one's own bootstraps: [5] 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 device or to write to the boot medium, it is usual for the boot program to use some system RAM as a RAM disk for temporary file 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 or miniature versions of Linux. 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 systems. 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.

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 Delete, F1, F2, F10 or F12), and then changing the boot order. [6] 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 F11 or F12). This results in a list of bootable devices being presented, from which a selection may be made.

Apple silicon Macs display the Boot Menu when the power button is pressed and held, the older Mac computers with Intel processors will display the Boot Menu if user presses the ⌥ Option or Alt while the machine is starting. [7]

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

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; [1] details vary.

FreeDOS
Linux
Windows Preinstallation Environment

See also

Related Research Articles

<span class="mw-page-title-main">BIOS</span> Firmware for hardware initialization and OS runtime services

In computing, BIOS is firmware used to provide runtime services for operating systems and programs and to perform hardware initialization during the booting process. The BIOS firmware comes pre-installed on an IBM PC or IBM PC compatible's system board and exists in some UEFI-based systems to maintain compatibility with operating systems that do not support UEFI native operation. The name originates from the Basic Input/Output System used in the CP/M operating system in 1975. The BIOS originally proprietary to the IBM PC has been reverse engineered by some companies looking to create compatible systems. The interface of that original system serves as a de facto standard.

A disk operating system (DOS) is a computer operating system that resides on and can use a disk storage device, such as a floppy disk, hard disk drive, or optical disc. A disk operating system provides a file system for organizing, reading, and writing files on the storage disk, and a means for loading and running programs stored on that disk. Strictly, this definition does not include any other functionality, so it does not apply to more complex OSes, such as Microsoft Windows, and is more appropriately used only for older generations of operating systems.

<span class="mw-page-title-main">Booting</span> Process of starting a computer

In computing, booting is the process of starting a computer as initiated via hardware such as a button 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.

<span class="mw-page-title-main">Drive letter assignment</span> Alphabetical assignment to logical drives on computers (e.g., C:\)

In computer data storage, drive letter assignment is the process of assigning alphabetical identifiers to volumes. Unlike the concept of UNIX mount points, where volumes are named and located arbitrarily in a single hierarchical namespace, drive letter assignment allows multiple highest-level namespaces. Drive letter assignment is thus a process of using letters to name the roots of the "forest" representing the file system; each volume holds an independent "tree".

<span class="mw-page-title-main">FreeDOS</span> Open source clone of MS-DOS

FreeDOS 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.

<span class="mw-page-title-main">Knoppix</span> Linux distribution

KNOPPIX is an operating system based on Debian designed to be run directly from a CD / DVD or a USB flash drive, one of the first live operating system distributions. Knoppix was developed by, and named after, Linux consultant Klaus Knopper. When starting a program, it is loaded from the removable medium and decompressed into a RAM drive. The decompression is transparent and on-the-fly.

<span class="mw-page-title-main">Boot sector</span> Sector of a persistent data storage device

A boot sector is the sector of a persistent data storage device which contains machine code to be loaded into random-access memory (RAM) and then executed by a computer system's built-in firmware.

<span class="mw-page-title-main">Live CD</span> Complete, bootable computer installation that runs directly from a CD-ROM

A live CD 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 from a hard disk drive. A live CD allows users to run an operating system for any purpose without installing it or making any changes to the computer's configuration. Live CDs can run on a computer without secondary storage, such as a hard disk drive, or with a corrupted hard disk drive or file system, allowing data recovery.

<span class="mw-page-title-main">SYSLINUX</span> Bootloader suite for Linux operating system

The Syslinux Project is a suite of five different boot loaders for starting up Linux distros on computers. It was primarily developed by H. Peter Anvin.

<span class="mw-page-title-main">USB flash drive</span> Data storage device

A USB flash 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 30 g (1 oz). Since first appearing on the market in late 2000, as with virtually all other computer memory devices, storage capacities have risen while prices have dropped. As of March 2016, flash drives with anywhere from 8 to 256 gigabytes (GB) were frequently sold, while 512 GB and 1 terabyte (TB) units were less frequent. As of 2018, 2 TB flash drives were the largest available in terms of storage capacity. Some allow up to 100,000 write/erase cycles, depending on the exact type of memory chip used, and are thought to physically last between 10 and 100 years under normal circumstances.

<span class="mw-page-title-main">Bootloader</span> Software responsible for starting the computer and load other software to the CPU memory

A bootloader, also spelled as boot loader or called boot manager and bootstrap loader, is a computer program that is responsible for booting a computer.

BIOS implementations provide interrupts that can be invoked by operating systems and application programs to use the facilities of the firmware on IBM PC compatible computers. Traditionally, BIOS calls are mainly used by DOS programs and some other software such as boot loaders. BIOS runs in the real address mode of the x86 CPU, so programs that call BIOS either must also run in real mode or must switch from protected mode to real mode before calling BIOS and then switching back again. For this reason, modern operating systems that use the CPU in Protected mode or Long mode generally do not use the BIOS interrupt calls to support system functions, although they use the BIOS interrupt calls to probe and initialize hardware during booting. Real mode has the 1MB memory limitation, modern boot loaders use the unreal mode or protected mode to access up to 4GB memory.

<span class="mw-page-title-main">BartPE</span>

BartPE is a discontinued tool that customizes Windows XP or Windows Server 2003 into a lightweight environment, similar to Windows Preinstallation Environment, which could be run from a Live CD or Live USB drive. A BartPE system image is created using PE Builder, a freeware program created by Bart Lagerweij.

<span class="mw-page-title-main">Live USB</span> USB drive with a full bootable operating system

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.

A volume boot record (VBR) is a type of boot sector introduced by the IBM Personal Computer. It may be found on a partitioned data storage device, such as a hard disk, or an unpartitioned device, such as a floppy disk, and contains machine code for bootstrapping programs stored in other parts of the device. On non-partitioned storage devices, it is the first sector of the device. On partitioned devices, it is the first sector of an individual partition on the device, with the first sector of the entire device being a Master Boot Record (MBR) containing the partition table.

The multi-stage booting process of Linux is in many ways similar to the BSD and other Unix-style boot processes, from which it derives.

<span class="mw-page-title-main">DOS</span> Group of closely related IBM PC-compatible operating systems

DOS is a family of disk-based operating systems for IBM PC compatible computers. The DOS family primarily consists of Microsoft's MS-DOS and a rebranded version, IBM PC DOS, both of which were introduced in 1981. Later compatible systems from other manufacturers include DR-DOS (1988), ROM-DOS (1989), PTS-DOS (1993), and FreeDOS (1998). MS-DOS dominated the IBM PC compatible market between 1981 and 1995.

A master boot record (MBR) is a special type of boot sector at the very beginning of partitioned computer mass storage devices like fixed disks or removable drives intended for use with IBM PC-compatible systems and beyond. The concept of MBRs was publicly introduced in 1983 with PC DOS 2.0.

The Ultimate Boot CD (UBCD) is a bootable CD-ROM containing a collection of diagnostic tools including CPU tests, memory tests, virus scanning, and other tools.

References

  1. 1 2 By J. D. Biersdorfer (October 8, 1998). "Emergency Preparedness". The New York Times .
  2. ↑ "How to Make a Compaq System Boot Disk". Hearst Newspapers.
  3. ↑ "How to Survive the Worst PC Disasters". PC World . May 23, 2007. p. 11. Archived from the original on October 27, 2020. Retrieved August 23, 2020. Download the demo and burn it to a bootable CD
  4. ↑ "Can I recover from recovering my PC?". Computerworld .
  5. ↑ a series of self-sustaining processes that proceed without external help: Martin, Gary. "'Pull yourself up by your bootstraps' - the meaning and origin of this phrase". Phrasefinder. Retrieved June 23, 2018.
  6. ↑ "How to enter your PC's BIOS". PC World . October 5, 2011. Need to change your computer's boot order or access other ..
  7. ↑ "Mac startup key combinations".
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