Glossary
Alpha
A RISC (Reduced Instruction Set
Computer) architecture developed by Digital Equipment Corporation.
ATAPI
An abbreviation for AT Attachement
Packet
Interface. ATAPI is the protocol by which CD-ROM drives communicate
with a computer system over an IDE interface.
Binary
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.''
BIOS
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.
Boot
Short for ``bootstrap.'' The process by which a
computer starts running an operating system when power is applied.
Boot Diskette
A diskette used to start many Red Hat Linux
installations.
Bootstrap
See ``Boot.''
CISC
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.
CMOS
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.
Cylinder
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.
Daemon
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.
Dependencies
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.
Diskette
A small mass storage device in a removable cartridge,
meant to be read/written to, in a compatible drive.
Distribution
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 ``finance.foo.com.''
Driver
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.
EIDE
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
Errata is Latin for ``Ooops.''8 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 http://www.redhat.com/errata.
Extended Partition
A segment of a disk drive that contains
other partitions. See Partition.
FAQ
An abbreviation for Frequently Asked Questions. Linux
information is often presented in the form of lists of questions and
answers called FAQs.
fdisk
fdisk is a utility program that is used to create,
delete or modify partitions on a disk drive.
Filesystem
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.
Floppy
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.''
Formatting
The act of writing a filesystem on a disk drive.
FQDN
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 ``bar.com,'' the FQDN would be
``foo.bar.com.''
FTP
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.
Gateway
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.
Geometry
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.
GID
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.
Group
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.
Head
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.
Hostname
A hostname is a human-readable string of characters
used to identify a particular computer system.
I18n
See Internationalization.
IDE
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.''
Intel
Company responsible for producing the microprocessors
that most commonly appear in PC-compatible personal computers. These
processors include the 80386, 80486, Pentium, Pentium Pro, and Pentium II.
Internationalization
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.
Kernel
The central part of an operating system upon which the
rest of the operating system is based.
Library
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.
LILO
A commonly-used bootstrap loader for Linux systems based
on an Intel-compatible processor.
Linus Torvalds
Created Linux in 1991 while a university
student.
Linuxconf
A versatile system configuration program written by
Jacques Gelinas. Linuxconf provides a menu-based approach to system
configuration via several different user interfaces.
Linux
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.
MBR
See ``Master Boot Record.''
Memory
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.
MILO
A commonly-used bootstrap loader for Linux systems based
on the Alpha processor.
Module
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.
Mount Point
The directory under which a filesystem is
accessible after being mounted.
Mount
The act of making a filesystem accessible to a system's
users.
Nameserver
In TCP/IP networking terms, a nameserver is a
computer that can translate a human-readable name (such as ``foo.bar.com'')
into a numeric address (such as ``10.0.2.14'').
Netmask
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.
NFS
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.
Packages
Files that contain software, and written in a
particular format that enables the software to be easily installed and
removed.
PAM
An acronym for Pluggable Authentication
Modules. PAM is an authentication system that controls access to
Red Hat Linux.
Partition
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
See PCMCIA.
PCMCIA
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.
Permissions
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.
PLIP
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.
POSIX
A somewhat mangled abbreviation for Portable
Operating System Interface. A set of standards that
grew out of the UNIX operating system.
Process
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.
RAM
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.
Reboot
To restart the boot process. See also ``Boot.''
Red Hat Software
A North Carolina software company. Produces
and markets sofware 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.
RISC
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.
ROM
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.
Root
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.''
RPM
An abbreviation that stands for Red Hat
Package
Manager. RPM is also the name of a program that enables the
installation, upgrading and removal of packages.
SCSI
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.
Sector
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.
setgid
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.
setuid
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.
SILO
A commonly-used bootstrap loader for Linux systems based
on the SPARC processor.
SLIP
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).
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.
SPARC
A RISC (Reduced Instruction Set
Computer) architecture developed by Sun Microsystems.
Swap
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 damand
paging.
System Call
A system call is a routine that accomplishes a
system-level function on behalf of a process.
TCP/IP
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.
UID
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.
UNIX
A set of Linux-like operating systems that grew out of an
original version written by some guys at a phone company.9
Unmount
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.
Widget
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.
XFree86
A free implementation of the X Window System.