Appendix A. Glossary


A RISC (Reduced Instruction Set Computer) architecture developed by Digital Equipment Corporation.


An abbreviation for AT Attachment Packet Interface. ATAPI is the protocol by which CD-ROM drives communicate with a computer system over an IDE interface.


Although the base two-numbering system used by computers is known as binary, the word often refers to the executable form of a program. Contrast with "source code."


An abbreviation for Basic Input/Output System. On PC-compatible systems, the BIOS is used to perform all necessary functions to properly initialize the system's hardware when power is first applied. The BIOS also controls the boot process, provides low-level input/output routines (hence its name) and (usually) allows the user to modify details of the system's hardware configuration.


Short for "bootstrap." The process by which a computer starts running an operating system when power is applied.

Boot Disk

A diskette used to start many Red Hat Linux installations.


See "Boot."


An abbreviation for Complex Instruction Set Computer. A design philosophy for computers whereby the processor is designed to execute a relatively large number of different instructions, each taking a different amount of time to execute (depending on the complexity of the instruction). Contrast with RISC.


Originally an abbreviation for Complementary Metal Oxide Semiconductor -- a semiconductor technology used in many integrated circuits. Now often used to describe the low-level hardware that contains a personal computer's BIOS setting, and the computer's hardware clock.


When referring to disk drives, the number of different positions the disk drive's read/write heads can take over the unit's disk platters. When viewed from above the platters, each head position describes an imaginary circle of different diameters on the platter's surface, but when viewed from the side, these circles can be thought of as a series of cylinders nested within each other, hence the term. See also Geometry.


A daemon is a program that runs, without human intervention, to accomplish a given task. For example, lpd is a daemon that controls the flow of print jobs to a printer.


When referring to packages, dependencies are requirements that exist between packages. For example, package foo may require files that are installed by package bar. In this example, bar must be installed, or else foo will have unresolved dependencies. RPM will not normally allow packages with unresolved dependencies to be installed.

Device Driver

Software that controls a device that is connected to, or part of, a computer.

Disk Drive

See Hard Disk.

Disk Druid

Disk Druid is a component of the Red Hat Linux installation program that is used to partition disk drives during the installation process.


A small mass storage device in a removable cartridge, meant to be read/written to, in a compatible drive.


An operating system (usually Linux) that has been packaged so as to be easily installed.

Domain Name

A domain name is used to identify computers as belonging to a particular organization. Domain names are hierarchical in nature, with each level in the hierarchy being separated from other levels with a period (pronounced "dot"). For example, Foo Incorporated's Finance department might use the domain name ""


See Device Driver.

Dual Boot

The act of configuring a computer system to boot more than one operating system. The name is something of a misnomer, as it is possible to boot more than the two operating systems the word "dual" implies.


An abbreviation for Enhanced Integrated Drive Electronics, which is a newer version of the IDE interface standard and another term for a particular implementation for IDE interfaces. EIDE makes larger and faster disk drives possible; most systems sold today use EIDE.


Errata is Latin for "Ooops."[1] When software is found to have bugs, quite often the software is fixed, and released as errata. Red Hat Linux is no exception to the rule; we have an Errata Web page at

Extended Partition

A segment of a disk drive that contains other partitions. See Partition.


An abbreviation for Frequently Asked Questions. Linux information is often presented in the form of lists of questions and answers called FAQs.


fdisk is a utility program that is used to create, delete or modify partitions on a disk drive.


A filesystem is the method by which information is stored on disk drives. Different operating systems normally use different filesystems, making it difficult to share the contents of a disk drive between two operating systems. However, Linux supports multiple filesystems, making it possible, for example, to read/write a partition dedicated to Windows.


A somewhat historical term for a small mass storage device in a removable cartridge, meant to be read/written to in a compatible drive. See "diskette."


The act of writing a filesystem on a disk drive.


An abbreviation for Fully Qualified Domain Name. An FQDN is the human-readable name that includes a computer's hostname and associated domain name. For example, given a hostname of "foo," and a domain name of "," the FQDN would be ""


An abbreviation for File Transfer Protocol. Also the name of a program that, as the name implies, permits the copying of files from one system on a network to another.


In networking terms, refers to a device that connects one or more computers on a network to other networks. The device may be specialized hardware (such as a router), or may be a general-purpose computer system configured to act as a gateway.


When referring to disk drives, the physical characteristics of the disk drive's internal organization. Note that a disk drive may report a "logical geometry" that is different from its "physical geometry," normally to get around BIOS-related limitations. See also Cylinder, Head and Sector.


Short for Group ID. The means by which a user's membership in a group is identified to various parts of Red Hat Linux. GIDs are numeric, although human-readable names are stored in the /etc/group file.


Groups are a way of assigning specific access rights to certain classes of users. For example, all users working on Project X could be added to group xproj. System resources (such as disk space) devoted to Project X could then be configured to permit only members of xproj full access.

Hard Disk

A hard disk contains rotating magnetic media (in the shape of disks) that spin rapidly. Small heads float over the surface of each disk, and are used to write to and read from the disk as it rotates.


When referring to disk drives, the number of read/write heads within a disk drive. For each platter in a disk drive, there are normally two heads for each platter -- one for each surface -- although one surface may go unused. See also Geometry.


A hostname is a human-readable string of characters used to identify a particular computer system.


See Internationalization.


An abbreviation for Integrated Drive Electronics, which is the name of a standard interface used to connect primarily disk and CD-ROM drives to a computer system. See also "EIDE" and "ATAPI."


Internet Message Access Protocol. A mail server type.


Company responsible for producing the microprocessors that most commonly appear in PC-compatible personal computers. These processors include the 80386, 80486, and the Pentium line.


The practice of designing and writing programs that can be easily configured to interact with the user in more than one language. Often referred to as "i18n," due to the number of letters between the starting "i" and the ending "n."

IP Address

IP addresses are the method by which individual computer systems (or from a more strictly accurate interpretation, the network interfaces on those computer systems) are identified on a TCP/IP network. All IP addresses consist of four number blocks, each ranging from 0 to 255, and separated by periods.


Internet Service Provider.


The central part of an operating system upon which the rest of the operating system is based.


When speaking of computers, refers to a collection of routines that perform operations which are commonly required by programs. Libraries may be shared, meaning that the library routines reside in a file separate from the programs that use them. Library routines may also be "statically linked" to a program, meaning that copies of the library routines required by that program are physically added to the program. Such statically linked binaries do not require the existence of any library files in order to execute. Programs linked against shared libraries will not execute unless the required libraries have been installed.


A commonly-used bootstrap loader for Linux systems based on an Intel-compatible processor.

Linus Torvalds

Created Linux in 1991 while a university student.


A versatile system configuration program written by Jacques Gelinas. Linuxconf provides a menu-based approach to system configuration via several different user interfaces.


A full-featured, robust, freely-available operating system originally developed by Linus Torvalds.

Logical Partition

A partition that exists within an extended partition. See also "partition" and "extended partition."

Master Boot Record

The master boot record (or MBR) is a section of a disk drive's storage space that is set aside for the purpose of saving information necessary to begin the bootstrap process on a personal computer.


See "Master Boot Record."


When referring to computers, memory (in general) is any hardware that can store data for later retrieval. In this context, memory usually specifically refers to RAM.


A commonly-used bootstrap loader for Linux systems based on the Alpha processor.


In Linux, a module is a collection of routines that perform a system-level function, and may be dynamically loaded and unloaded from the running kernel as required. Often containing device drivers, modules are tightly bound to the version of the kernel; most modules built from one version of a kernel will not load properly on a system running another kernel version.


The act of making a filesystem accessible to a system's users.

Mount Point

The directory under which a filesystem is accessible after being mounted.

Name Server

In TCP/IP networking terms, a name server is a computer that can translate a human-readable name (such as "") into a numeric address (such as "").


A netmask is a set of four number blocks separated by periods. Each number is normally represented as the decimal equivalent of an eight-bit binary number, which means that each number may take any value between 0 (all eight bits cleared) and 255 (all eight bits set). Every IP address consist of two parts (the network address and the host number). The netmask is used to determine the size of these two parts. The positions of the bits that are set in the netmask are considered to represent the space reserved for the network address, while the bits that are cleared are considered to represent the space set aside for the host number.


An abbreviation for Network File System, NFS is a method of making the filesystem on a remote system accessible on the local system. From a user's perspective, an NFS-mounted filesystem is indistinguishable from a filesystem on a directly-attached disk drive.

Operating System

A collection of software that controls various resources of a computer.


Files that contain software, and written in a particular format that enables the software to be easily installed and removed.


An acronym for Pluggable Authentication Modules. PAM is an authentication system that controls access to Red Hat Linux.


A segment of a disk drive's storage space that can be accessed as if it was a complete disk drive.

Partition Table

The partition table is a section of a disk drive's storage space set aside to define the partitions that exist on that disk drive.

Partition Type

Partitions contain a field that is used to define the type of filesystem the partition is expected to contain. The partition type is actually a number, although many times the partition type is referred to by name. For example, the "Linux Native" partition type is 82. Note that this number is hexadecimal.

PC Card



Acronym for Personal Computer Memory Card International Association. This organization produced a series of standards that define the physical, electrical and software characteristics of small, credit card-sized devices that can contain memory, modems, network adapters and more. Also known as PC Cards, these devices are mainly used in laptop computers (although some desktop systems can use PCMCIA cards, too).

PCMCIA Support Diskette

A diskette required for Red Hat Linux installations that require the use of a PCMCIA device during the install.


The set of identifiers that control access to files. Permissions consist of three fields: user, group, and world. The user field controls access by the user owning the file, while the group field controls access by anyone matching the file's group specification. As the name implies, the world field controls access by everyone else. Each field contains the same set of bits that specify operations that may or may not be performed, such as reading, writing and executing.


An abbreviation for Parallel Line Internet Protocol. PLIP is a protocol that permits TCP/IP communication over a computer's parallel port using a specially-designed cable.


Post Office Protocol. A mail server type.


A somewhat mangled abbreviation for Portable Operating System Interface. A set of standards that grew out of the UNIX operating system.


Point-to-Point Protocol. A protocol that permits a dialup connection to an Internet Service Provider.


A process (in somewhat simplistic terms) is one instance of a running program on a Linux system.

PS/2 Mouse

A PS/2 mouse gets its name from the original computer in which this type of mouse was first used -- the IBM PS/2. A PS/2 mouse can be easily identified by the small, round connector at the end of its cable.


An acronym for Random Access Memory. RAM is used to hold programs while they are being executed, and data while it is being processed. RAM is also volatile, meaning that information written to RAM will disappear when the computer's power is turned off.

RAM disk

A virtual drive which uses part of a computer's RAM to store data. A RAM disk provides quick access to information, but unlike written data, that data in a RAM disk is lost when the computer is turned off.


To restart the boot process. See also "Boot."

Red Hat, Incorporated

A North Carolina software company. Produces and markets software for the Linux operating system, including Red Hat Linux.

Rescue Diskette

A diskette containing a rudimentary system environment. As the name implies, a rescue diskette is normally used in an attempt to "rescue" an ailing system from the necessity of re-installing the entire operating system.


An abbreviation for Reduced Instruction Set Computer. A design philosophy for computers whereby the processor is optimized to execute a relatively small number of different instructions in a predictably small amount of time. Contrast with CISC.


An abbreviation for Read Only Memory. ROM is used to hold programs and data that must survive when the computer is turned off. Because ROM is non-volatile; data in ROM will remain unchanged the next time the computer is turned back on. As the name implies, data cannot be easily written to ROM; depending on the technology used in the ROM, writing may require special hardware, or may be impossible. A computer's BIOS may be stored in ROM.


The name of the login account given full and complete access to all system resources. Also used to describe the directory named "/"as in, "the root directory."


An abbreviation that stands for RPM Package Manager. RPM is also the name of a program that enables the installation, upgrading and removal of packages.


An abbreviation for Small Computer System Interface, SCSI is a standard interface for connecting a wide variety of devices to a computer. Although the most popular SCSI devices are disk drives, SCSI tape drives and scanners are also common.


When referring to disk drives, the number of fixed-size (normally 512 byte) areas that can be accessed by one of the disk drive's read/write heads, in one rotation of the disk, without that head changing position. See Also Geometry.

Serial Mouse

A serial mouse is a mouse that is designed to be connected to a computer's serial port. A serial mouse can be easily identified by the rectangular-shaped connector at the end of its cable.


A system call that can be used to set the GID of a process. Programs can be written using setgid such that they can assume the group ID of any group on the system.


A system call that can be used to set the UID of a process. Programs can be written using setuid such that they can assume the user ID of any process on the system. This is considered a possible security problem if a program is "setuid root."

Shadow Password

Normally, each user's password is stored, encrypted, in the file /etc/passwd. This file must be readable by all users so that certain system functions will operate correctly. However, this means that copies of user's encrypted passwords are easily obtained, making it possible to run an automated password-guessing program against them. Shadow passwords, on the other hand, store the encrypted passwords in a separate highly-protected file, making it much more difficult to crack passwords.


A commonly-used bootstrap loader for Linux systems based on the SPARC processor.


An acronym for Serial Line Internet Protocol. SLIP is a protocol that permits TCP/IP communication over serial line (typically over a dial-up modem connection).


Short for Server Message Block, SMB is the communications protocol used by Windows-based operating systems to support sharing of resources across a network.


Simple Mail Transfer Protocol. A mail server type.

source code

The human-readable form of instructions that comprise a program. Also known as "sources." Without a program's source code, it is very difficult to modify the program.


A RISC (Reduced Instruction Set Computer) architecture developed by Sun Microsystems.


Also known as "swap space." When a program requires more memory than is physically available in the computer, currently-unused information can be written to a temporary buffer on the hard disk, called swap, thereby freeing memory. Some operating systems support swapping to a specific file, but Linux normally swaps to a dedicated swap partition. A misnomer, the term swap in Linux is used to define demand paging.

System Call

A system call is a routine that accomplishes a system-level function on behalf of a process.


An abbreviation for Transmission Control Protocol/Internet Protocol, TCP/IP is the name given to the networking standard commonly used on the Internet today.

Torvalds, Linus

See Linus Torvalds.


Short for User ID. The means by which a user is identified to various parts of Red Hat Linux. UIDs are numeric, although human-readable names are stored in the /etc/passwd file.


A set of Linux-like operating systems that grew out of an original version written by some guys at a phone company.[2]


The act of revoking access to a filesystem. (Note that the program that unmounts filesystems is called umount.)

Virtual Console

Virtual consoles provides multiple "screens" on which a user may log in and run programs. One screen is displayed on the computer's monitor at any given time; a key sequence is used to switch between virtual consoles.


A standardized on-screen representation of a control that may be manipulated by the user. Scroll bars, buttons, and text boxes are all examples of widgets.

X Window System

Also known as "X," this graphical user interface provides the well-known "windows on a desktop" metaphor common to most computer systems today. Under X, application programs act as clients, accessing the X server, which manages all screen activity. In addition, client applications may be on a different system than the X server, permitting the remote display of the applications graphical user interface.


A free implementation of the X Window System.



Well, it should be…


Just kidding -- thank you Ken Thompson and Dennis Ritchie of Bell Telephone Laboratories for your inspired operating system design!