A P P E N D I X B
Glossary of Linux Terms
This appendix provides brief explanations of common terms used in the Linux and UNIX environments. These include technical terms, as well as conventions used in the Linux community. Because of space limitations, this glossary is somewhat selective but still should prove a lasting reference as well as a helpful guide for those new to Linux.
Cross-referenced terms are highlighted in italics.
Symbols
.
In the context of file management at the command-line prompt, this symbol refers to the current directory.
..
In the context of file management at the command-line prompt, this symbol refers to the parent directory of that currently being browsed.
/
In the context of file management at the command-line prompt, the forward slash refers to the root of the file system; it also separates directories in a path listing.
~
In the context of file management at the command-line prompt, the tilde refers to a user’s home directory.
|
The pipe symbol is used at the command-line prompt to pipe output from one command to another.
When used at the command-line prompt, the right angle bracket indicates that output should redirect into a file.
<
When used at the command-line prompt, the left angle bracket indicates that a command should accept input from a file (see redirect).
#
When it appears at the command-line prompt, this symbol usually indicates that the user is currently logged in as root.
$
When it appears at the command-line prompt, the dollar sign usually indicates that the user is currently logged in as an ordinary user. (Note that some versions of Linux/UNIX use % or > instead of $.)
?
The question mark is a wildcard character indicating that any character can be substituted in its place; this symbol is typically relevant only at the command-line prompt.
*
The asterisk is a wildcard character indicating that zero or more characters can appear in its place; this symbol is typically relevant only at the command-line prompt.
*nix
Popular but unofficial way of describing the family tree that comprises UNIX and its various clones, such as Linux and Minix.
A
administrator
A user on the system with ultimate power to configure the system. Usually under standard Linux installations, this is another word for either the root user or one who has adopted that user’s powers temporarily.
AIX
IBM’s proprietary form of UNIX that runs on the company’s proprietary hardware, as well as commodity hardware based around AMD and Intel processors. Nowadays, IBM is slowly deprecating AIX in favor of Linux.
alias
Method of creating a user-defined command that, when typed, causes another command to be run or a string to be expanded.
Popular open source web server software that runs on UNIX, Linux, and other operating system platforms. Considered responsible in part for the rise in popularity of Linux in the late 1990s.
applet
Small program that, in the context of the Ubuntu Desktop, runs as part of a larger program and offers functions that complement the main program. The GNOME desktop incorporates several applets, and—technically speaking—all features or elements of the panels are applets, including even the main menus.
APT
Advanced Packaging Tool; the underlying system by which software is managed and installed on Ubuntu and Debian Linux systems. Shell commands beginning with apt, such as apt-get, are used to install new software from various repositories. Under Ubuntu, the Synaptic Package Manager program provides a GUI method of using APT.
archive
Any file containing a collection of smaller files, compressed or otherwise (see also tar).
B
BASH
Bourne Again SHell. The most common shell interpreter used under Linux and offered as the default on many Linux systems. Based on the older Bourne sh software.
binary executable
Another way of referring to a program that has been compiled so that it can be used day to day. See also compilation.
block device
How the Linux kernel communicates with a device that sends and receives blocks of data; usually a hard disk or removable storage device. See also character device.
BSD UNIX
Berkeley Software Distribution UNIX; form of UNIX partially based on the original UNIX source code but also incorporating recent developments. BSD is open source and free for all to use and share, with practically no restrictions. There are various forms of BSD UNIX, such as FreeBSD, NetBSD, and OpenBSD. BSD doesn’t use the Linux kernel but runs many of the same programs. Some of the programs offered within the Linux OS come from BSD.
bzip2
Form of file compression. Together with the older and less-efficient gzip, it is a popular form of file compression under Linux and the equivalent to Zip compression under Windows. Files employing bzip compression are usually given a .bz2 file extension (tar files are usually given the double file extension .tar.bz2, or occasionally just .tbz). See also tar.
C
C
Programming language in which much of the Linux kernel is written, as were later versions of UNIX before it. C was created by some of the same people who created UNIX, and its development mirrors that of UNIX.
C++
Object-oriented programming language; originally designed to be an enhancement to C, but now seen as a popular alternative.
C#
Modern programming language, which uses similar syntax to C, created by Microsoft and re-created on Linux via the Mono project.
character device
How Linux refers to a device that sends/receives data asynchronously. For various technical reasons, this typically refers to the terminal display. See also block device.
checksum
Mathematical process that can be applied to a file or other data to create a unique number relative to the contents of that file. If the file is modified, the checksum will change, usually indicating that the file in question has failed to download correctly or has been modified in some way. The most common type of checksum program used under Linux and UNIX is md5sum.
client
Shorthand referring to a computer (or software) that connects to a server.
closed source
The reverse of open source, in which the source code is not available for others to see, share, or modify. See also proprietary.
code
See source code.
command
Input typed at the shell that performs a specific task, usually related to administration of the system and/or the manipulation of files.
See shell.
commodity
In the context of hardware, describes PC hardware usually based around Intel or AMD processors that can be bought off the shelf and used to create sophisticated computer systems (as opposed to buying specially designed hardware). One reason for Linux‘s success is its ability to use commodity hardware.
community
The general term for the millions of Linux users worldwide, regardless of what they use Linux for or their individual backgrounds. By using Linux, you automatically become part of the community.
compilation
The practice of creating a binary file from source code, usually achieved using the ./configure, make, make install series of commands and scripts.
config file
Configuration file; any file that contains the list of settings for a program. Sometimes it’s necessary to edit config files by hand by using programs such as vi or Emacs, but often the program itself will write its config file according to the settings you choose.
copyleft
The legal principle of protecting the right to share a creative work, such as a computer program, using a legally binding license. Copyleft also ensures that future iterations of the work are covered in the same way.
cracker
Someone who breaks into computer systems to steal data or cause damage. The term is not necessarily linked to Linux or UNIX but was created by the community to combat the widespread use of hacker in this sense. The word hacker has traditionally defined someone who merely administers, programs, and generally enjoys computers.
cron
Background service that schedules tasks to occur at certain times. It relies on the crontab file.
CUPS
Common UNIX Printing System; set of programs that work in the background to handle printing under UNIX and Linux.
curses
Library that lets software present a semigraphical interface at the shell, complete with menu systems and simple mouse control (if configured). The version of curses used under Linux and UNIX is called ncurses.
Concurrent Versions System; application that allows the latest version of software packages to be distributed over the Internet to developers and other interested parties. Nowadays Git or Subversion are preferred instead and work along similar lines.
D
daemon
See service.
Debian
Community organization that produces distributions of free software operating systems, including Linux. Because it is a nonprofit organization run by passionate free software advocates, it is considered the most ethically sound of all Linux outfits. Many distributions, including Ubuntu, use Debian as the basis for their software because of its claimed reliability, relative simplicity, and certain sophisticated features, such as the APT software management system.
dependency
A way of referring to system files or other software that a program requires in order to run. If the dependencies are not present during program installation, a program might refuse to install.
device
Linux shorthand describing something on your system that provides a function for the user or that the system requires in order to run. This usually refers to hardware, but it can also describe a virtual device that is created to provide access to a particular Linux function.
directory
What Windows refers to as a folder; areas on a hard disk in which files can be stored and organized.
distribution
A collection of software making up the Linux operating system; also known as a distro. The software is usually compiled by either a company or organization. A distribution is designed to be easy to install, administer, and use by virtue of it being an integrated whole. Examples include Ubuntu, SUSE Linux, Red Hat, and Debian.
distro
Shorthand for distribution.
documentation
Another way of describing written guides or instructions; can refer to online sources of help as well as actual printed documentation.
Debian package management system; shell command that can be used to administer software under Ubuntu and Debian. However, the APT system, which uses dpkg, is the preferred method of installing software.
E
Edubuntu
Official spin-off of the main Ubuntu project that features educational software along with a child-friendly user interface and classroom administration software. Unlike other spin-off projects, such as Xubuntu and Kubuntu, Edubuntu features the same GNOME interface as the main Ubuntu release, and much of the same software.
Emacs
Seminal text editor and pseudo-shell beloved by UNIX aficionados; can be used for programming tasks, simple word processing, and much more. This editor has cultural significance as one of the core pieces of software offered by the GNU Project. Emacs was originally developed principally by Richard Stallman. See also vi.
environment
Shorthand referring to a user‘s unique Linux configuration, such as variables that tell the shell where programs are located.
F
FAT32
File Allocation Table 32-bits; file system offered by Windows 98, Me, 2000, and XP. Linux can both read and write to FAT32 file systems. See also NTFS and VFAT.
Firefox
Web browser program used under Ubuntu and produced by the Mozilla Foundation.
FLOSS
Free, libre, or open source software; used within the community to describe all software or technology that, broadly speaking, adheres to the ethical approach of open source software and/or free software, as well as its legal guidelines.
FOSS
Free or open source software; alternative term for FLOSS.
When used to describe software or associated areas of technology, free indicates that the project abides by the ethical (if not legal) guidelines laid down by the GNU Project. It doesn’t necessarily indicate that the software is free in a monetary sense; its meaning is quite different from freeware.
Free software
Software in which the source code—the original listing created by the programmer—is available for all to see, share, study, and adapt to their own needs. This differs from the concept of open source, because the right of others to further modify the code is guaranteed via the GNU Public License (GPL) software license (or a compatible license). For various reasons, in some instances free software does not include the source code (although the software can still be legally decompiled), but this is rare.
Free Software Foundation
Nonprofit organization founded by Richard Stallman to effectively sponsor the creation of the GNU operating system, and further the aims and goals of free software (including the legal documents, such as the GPL). It is considered the home of the free software ideal and GNU itself. Sometimes abbreviated as FSF.
G
GCC
GNU Compiler Collection; programs used when creating binary executable files from source code. Formerly called GNU C Compiler.
GID
Group ID; numbering system used by the operating system to refer to a group.
GIMP
GNU Image Manipulation Program; high-powered image-editing program that runs under Linux, UNIX, Windows, and other operating systems. Often preceded by the definite article: The GIMP.
GNOME
A GUI-based desktop environment used by Ubuntu as well as several other distributions. It uses the GTK+ libraries. The name was originally created as an acronym standing for GNU Network Object Model Environment, but now the term is considered a word and not an acronym. See also KDE.
GNU
GNU’s Not UNIX; seminal operating system project initiated by Richard Stallman in 1983 and intended to form a free software clone of UNIX. See GNU Project.
Another name for the operating system referred to as Linux. The name GNU/Linux gives credit to the vast quantity of GNU Project software that is added to the Linux kernel within a distro to make a complete operating system. As such, GNU/Linux is the preferred term of many free software advocates.
GNU Project
Organization created by Richard Stallman in order to further the aims of free software and create the body of software that makes up the GNU operating system.
GNU Public License
Software license principally created by Richard Stallman in order to protect software source code against proprietary interests and ensure that it will always be shared. It does this by insisting that any source code covered by the GNU Public License (GPL) must remain licensed under the GPL, even after it has been modified or added to by others. The Linux kernel, as well as much of the software that runs on it, uses the GPL. There are several versions of the GNU Public License that refine its requirements and limitations (notably versions 2 and 3), and several variations designed for other uses; key examples include the Lesser GPL (LGPL), which relinquishes some requirements of the GPL and is usually used with library software, and the GNU Free Documentation License that, as its name suggests, is usually used to license technical literature, such as manuals.
GPL
See GNU Public License.
grep
Global regular expression print; powerful shell command that lets you search a file or other form of input by using regular expressions. Because of the ubiquity of the grep program, many Linux and UNIX users refer to searching as grepping. To grep a file is to search through it for a string.
group
Collection of users under one heading (group name) to facilitate system administration.
GRUB
GRand Unified Bootloader; boot manager program that offers a menu from which you can choose which operating system you wish to boot. It’s needed to load the kernel program and thereby initiate the Linux boot procedure.
GUI
Graphical user interface; describes the software that provides a graphical system to display data and let you control your PC (usually via a mouse).
guru
One who is experienced and knowledgeable about Linux/UNIX and is willing to share his or her knowledge with others. In a perfect world, every newbie would have his or her own guru.
One of the two preferred forms of file compression used under Linux. Files employing gzip compression usually have a .gz file extension. See also bzip2.
H
hack
Ingenious and/or extremely efficient solution to a problem, particularly within the programming world.
hacker
Term used within the community to describe anyone who enjoys computers and possesses some skill therein, either in a professional capacity or as a hobby. A positive and highly valued term, the word is distinct from connotations of maliciously breaking into computers propagated by the media. See also cracker.
host
Shorthand referring to any computer that acts as a server to another computer. See also client.
HP-UX
Hewlett-Packard’s proprietary form of UNIX designed to work on its own hardware platform.
Hurd
Kernel developed by the GNU Project and originally intended to form the centerpiece of the GNU operating system. However, with the arrival of the Linux kernel, its necessity was lessened, and it is now arguably a minor project. It’s not associated with the Linux kernel in any way.
I
info
Source of documentation accessible from the shell; an alternative to the more established man page system. Also known as Texinfo.
init
With most versions of Linux, init is the program that is automatically run after the kernel has finished loading, and therefore early in the boot procedure. It’s responsible for effectively starting the operating system. Under Ubuntu, a system called Upstart is used instead, but it is 100 percent backward-compatible with the way init works, to the extent that those not knowing Upstart was in use would not realize the difference.
Collection of startup scripts that make up the components of a run level. Under Ubuntu, these are found at /etc/init.d. Symbolic links to selected init.d scripts are contained in folders within /etc/init.d that are named after run level numbers, such as rc0.d, rc1.d, rc2.d, and so on.
initrd
Initial RAM disk; system used by the Linux kernel to load modules that are essential for the kernel to be able to boot, such as disk controllers.
inode
Part of the usually invisible file system structure that describes a file, such as its ownership permissions or file size.
ipchains
Now-deprecated component of version 2.2 of the Linux kernel that allows the creation of network security setups, such as firewalls or port-forwarding arrangements. Note that some distros still prefer to use ipchains. See also iptables.
iptables
Component of versions 2.4 and 2.6 of the Linux kernel that allows powerful network security setups via the configuration of netfilter. Chiefly used in the creation of firewalls, but can be used for more elementary arrangements such as network address translation (NAT) routers. Ubuntu offers a far more user-friendly command-line tool called ufw that aids configuration of iptables.
J
job
How the BASH shell refers to a running program in order to facilitate administration by the user.
journaling
File system technology in which integrity is maintained via the logging of disk writes.
K
KDE
K Desktop Environment; GUI and set of additional programs used on various distros, such as Mandriva and a variation of Ubuntu called Kubuntu.
kernel
Essential but ordinarily invisible set of programs that run the computer’s hardware and provide a platform on which to run software. In the Linux operating system, the kernel is also called Linux, after its creator, Linus Torvalds.
Error message that appears when the kernel program in Linux cannot continue to work. In other words, a polite way of indicating a crash or, more often, a problem arising from user misconfiguration. This is most often seen when booting up after making incorrect changes to the system.
kludge
Community slang describing an inelegant way of making something work, usually not in a way that is generally accepted as being correct. Pronounced kloodge.
Kubuntu
Version of Ubuntu that substitutes the GNOME desktop environment for KDE.
L
LAMP
Acronym describing a series of programs that work together to provide a complete Linux-based web-hosting environment. Stands for Linux, Apache, MySQL, and PHP, Python, or Perl (the last three in the list are scripting languages; see script).
LGPL
Lesser GPL; version of the GNU Public License (GPL) in which some use restrictions are slackened at the expense of various freedoms laid down by the main GPL. The LGPL is mostly used for library files.
library
General term referring to code that programs need to run and that, once in memory, is frequently accessed by many programs (leading to the phrase “shared library”). The most common and vital library is glibc (GNU C Library), created by the GNU Project and the fundamental building block without which Linux could not operate. GNOME relies on the GTK+ libraries, among others.
link
File system method of assigning additional filenames to a block of data that represents a file; also known as a “hard link.” See also symbolic link.
Linux
(1) A kernel program created by Linus Torvalds in 1991 to provide an inexpensive operating system for his computer, along with other components.
(2) The entire operating system discussed in this book, although many argue (perhaps quite rightly) that this is inaccurate, and use the term GNU/Linux instead, to give credit to the inclusion of many components of the GNU operating system.
A nonprofit organization that aims to further the adoption of the Linux operating system, and as such is sponsored by many corporations that utilize the Linux OS as part of their business, such as IBM and Novell. It is considered the spiritual home of Linux, if such a distinction can be made, and employs Linus Torvalds, the originator and leader of the Linux kernel project.
local
Shorthand referring to the user‘s PC or a device directly attached to it (as opposed to remote).
localhost
Network name used internally by Linux and software to refer to the local computer, distinct from the network.
M
man page
Concise technical documentation accessible from the shell that describes a command and how it should be used.
Minix
Created by Andrew Tanenbaum, this operating system is a rough clone of UNIX. It was the operating system that Linus Torvalds had in mind when devising Linux, and which acted as an early development platform for him.
module
Program code that can be inserted or removed from the kernel in order to support particular pieces of hardware or provide certain kernel functions. Drivers under Windows perform the same function.
mount
To add a file system so that it is integrated (and therefore accessible) within the main file system; applies to external file systems, such as those available across networks, as well as those on the local PC, such as the hard disk or CD/DVD-ROMs.
Mozilla Foundation
Organization founded by Netscape to create open source Internet software, such as web browsers and e-mail clients; originally based on the Netscape source code. At the time of this writing, it produces the Firefox and Camino web browsers, the Thunderbird e-mail and Usenet client, the Bugzilla bug-tracking software, as well as other programs. The underlying web-browsing engine software used by many Mozilla Foundation products is known as Gecko.
MySQL
Popular and powerful open source database application. See also LAMP.
N
newbie
Term used to describe anyone who is new to Linux and therefore still learning the basics. It’s not a derogatory term! See also guru.
NFS
Network File System; reliable and established method of sharing files, printers, and other resources across a network of UNIX-based operating systems. See also Samba.
NTFS
NT File System; file system offered by Windows NT, 2000, XP, and Vista. It is usually fully accessible under Linux, although some distributions do not allow writing to NTFS partitions. See also FAT32.
O
open source
(1) Method and philosophy of developing software whereby the source code—the original listing created by the programmer—is available for all to see. Note that open source is not the same as free software; describing software as open source doesn’t imply that the code can be shared or used by others (although this is often the case).
(2) A community of users or any project that adheres to open source values and/or practices.
OpenOffice.org
Open source office suite project created with the continuing input of Sun Microsystems (now part of Oracle) and based on code Sun contributed to the open source community. Oracle commercializes a proprietary version called Oracle Open Office (previously known as StarOffice).
P
partition
Subdivision of a hard disk into which a file system can be installed.
PID
Process ID; the numbering system used to refer to a process.
pipe
Method of passing the output from one command to another for further processing. Piping is achieved within the shell by typing the | symbol.
Portable Operating System Interface; various technical standards that define how UNIX-like operating systems should operate and to which the Linux operating system attempts to adhere.
PPP
Point-to-Point Protocol; networking technology that allows data transfer across serial connections such as telephone lines. In other words, it’s the technology that lets you connect to your Internet service provider by using a modem.
process
The way the system refers to the individual programs (or components of programs) running in memory.
proprietary
Effectively, software for which a software license must be acquired, usually for a fee. This usually means that the source code is kept secret, but it can also indicate that the source code is available to view but not to incorporate into your own projects or share with others.
R
Red Hat
Well-known company that produces distributions of Linux.
redirect
Used to send the output of a command into a particular file. This also works the other way around: the contents of a particular file can be directed into a command. Redirection is achieved within the shell by using the left and right angle brackets (< and >), respectively.
regex
See regular expression.
regular expression
Powerful and complex method of describing a search string, usually when searching with tools such as grep (although regular expressions are also used when programming). Regular expressions use various symbols as substitutes for characters or to indicate patterns.
remote
Indicates a computer or service that is available across a network, including but not limited to computers on the Internet (as opposed to local).
root
(1) The bottom of the Linux file system directory structure, usually indicated by a forward slash (/).
(2) The /root directory in the bottom of the file system, which is effectively the root user’s personal directory.
(3) The hard disk partition on which operating system files are installed, sufficient to boot Linux; under Ubuntu the root partition contains all operating system and user data files.
(4) The user on some versions of UNIX or Linux who has control over all aspects of hardware, software, and the file system.
(5) Used to describe a user who temporarily takes on the powers of the root user (via the sudo command, for example).
RPM
Red Hat Package Manager; system used to install and administer programs under Red Hat, SUSE Linux, and some other distributions. The equivalent of APT.
RTFM
Read the Fine manual/man page; exclamation frequently used online when a newbie asks for help without having undertaken basic research.
run level
Describes the current operational mode of Linux (typically, the services that are running). Run level 1 is single-user mode (a stripped-down system with minimal running services); run levels 2 through 5 provide a GUI; run level 6 is reboot mode (switching to it will cause the computer to terminate its processes and then reboot); run level 0 is shutdown (switching to it will cause the PC to shut down). Under Ubuntu and most derivatives of Debian, run level 2 is the default.
S
Samba
Program that re-creates under UNIX or Linux the Microsoft SMB-based system of sharing files, printers, and other computer resources across a network. It allows Linux to become a file or printer server for Linux and Windows computers, and also allows a Linux client to access a Windows-based server.
scalable
Term describing the ability of a single computer program to meet diverse needs, regardless of the scale of the potential uses. The Linux kernel is described as being scalable because it can run supercomputers as well as handheld computers and home entertainment devices.
script
Form of computer program consisting of a series of commands in a text file. Most shells allow some form of scripting, and entire programming languages such as Perl are based around scripts. In the context of the Linux OS, shell scripts are usually created to perform trivial tasks or ones that frequently interact with the user. Shell scripts have the advantage that they can be frequently and easily modified. The Linux boot process relies on several complex scripts to configure essential system functions such as networking and the GUI. See also init and Upstart.
server
(1) Type of computer designed to share data with other computers over a network.
(2) Software that runs on a computer and is designed to share data with other programs on the same PC or with other PCs across a network.
service
Background program that provides vital functions for the day-to-day running of Linux; also known as a daemon. Services are usually started when the computer boots up and as such are constituent parts of a run level.
shell
Broadly speaking, any program that creates an operating environment in which you can control your computer. The GNOME Desktop can be seen as a shell, for example. However, it’s more commonly understood within UNIX and Linux circles as a program that lets you control the system by using commands entered at the keyboard. In this context, the most common type of shell in use on Linux is BASH.
Shuttleworth, Mark
Entrepreneurial South African businessman who, as a long-term Debian hacker, devised and financially supports Ubuntu via his company, Canonical Ltd.
SMB
Server Message Block; network technology for sharing files, printers, and other resources. See also Samba.
Solaris
Form of UNIX sold by Sun Microsystems (now part of Oracle); runs on proprietary hardware systems as well as on commodity systems based on Intel and AMD processors. Available in an entirely open source rendition called OpenSolaris.
source code
The original program listing created by a programmer. Most programs that you download are precompiled—already turned into binary executables ready for general use—unless you specifically choose to download and compile the source code of a program yourself.
SSH
Secure SHell; program that lets you access a Linux/UNIX computer across the Internet. SSH encrypts data sent and received across the link.
Secure Sockets Layer; form of network data transfer designed to encrypt information for security purposes. It’s used online for certain web sites and also within Linux for certain types of secure data exchange.
Stallman, Richard M.
Legendary hacker who founded the GNU Project and created the concept of copyleft, as well as the software license that incorporates it: the GNU Public License (GPL). See also Linus Torvalds.
standard error
Linux and UNIX shorthand for the error output provided by a command.
standard input
Linux and UNIX shorthand for the device usually used to provide input to the shell. For the majority of desktop PC users, this refers to the keyboard.
standard output
Linux and UNIX shorthand for the device usually used to display output from a command. For the majority of desktop PC users, this refers to the screen.
string
A word, phrase, or sentence consisting of letters, numbers, or other characters that is used within a program and is often supplied by the user.
sudo
Program that runs under UNIX and Linux by which ordinary users are temporarily afforded administrator rights. Ubuntu relies on sudo as the exclusive way for users to administer the system. The equivalent command to start GUI applications under Ubuntu is gksu.
SVG
Scalable Vector Graphics; vector graphics technology. SVG is actually an XML markup language designed to create 2D graphics, increasingly used for Linux desktop icons and web graphics.
swap
Area of the hard disk that the Linux kernel uses as a temporary memory storage area. Desktop or server Linux differs from Windows in that it usually requires a separate hard disk partition in which to store the swap file.
symbolic link
Type of file akin to a Windows shortcut. Accessing a symbolic link file routes the user to an actual file. See also link.
Systems administrator; a way of describing the person employed within a company to oversee the computer systems. In such an environment, the sysadmin usually is the root user of the various computers.
System V
Variant of UNIX used as a foundation for modern forms of proprietary UNIX.
T
tainted
Describes a kernel that is using proprietary modules in addition to open source modules. Can also refer to insecure software.
tar
Tape ARchive; software able to combine several files into one larger file in order to back them up to a tape drive or simply transfer them across the Internet. Such files are usually indicated by a .tar file extension. Note that a tar file isn’t necessarily compressed; the bzip2 and gzip utilities must be used if this is desired.
TCP/IP
Transmission Control Protocol/Internet Protocol; standard protocol stack used by most modern operating systems to control and communicate across networks and also across the Internet (as opposed to NetBEUI, commonly available on older versions of Windows, and IPX/SPX, used on Novell’s NetWare operating system).
terminal
Another word for shell.
TeX
Method and set of programs for typesetting complex documents. Invented prior to word processors and desktop publishing software, and now considered a specialized tool for laying out scientific texts. An updated version of the program called LaTeX is also available.
Torvalds, Linus
Finnish programmer who, in 1991, created the initial versions of the Linux kernel. Since then, he has utilized an international network of volunteers and staff employed by various companies who help produce the kernel. Torvalds himself contributes to and oversees the efforts and is employed by the Linux Foundation.
tty
TeleTYpewriter; shorthand referring to underlying Linux virtual devices that allow programs and users to access the kernel and thereby run programs.
The name of the penguin character that is the Linux mascot. The original Tux graphic was drawn by Larry Ewing.
U
Ubuntu
Linux distribution with several unique characteristics. Ubuntu is designed primarily for desktop use (although other versions are available, including some for server hardware and for handheld computers). It is intended for use by individuals in any location in the world, so it has strong multiple-language support. It’s run by the Ubuntu Foundation, which is financially backed by Mark Shuttleworth. Each release is guaranteed to be supported for 18 months, or three years in the case of long-term support (LTS) releases (five years in the case of server releases).
Ubuntu Foundation
Organization set up by Mark Shuttleworth and his company, Canonical Ltd., to provide an official home for the Ubuntu distribution of Linux.
UID
User ID; numbering system used by the operating system to refer to a user.
UNIX
Seminal operating system created as a research project in 1969 by Kenneth Thompson and Dennis Ritchie at Bell Labs (later AT&T). Because it was initially possible to purchase the source code for a fee, subsequent revisions were enhanced by a variety of organizations and went on to run many mainframe and minicomputer systems throughout the 1980s, 1990s, and up to the present. Nowadays, UNIX is fragmented and exists in a variety of versions. Perhaps most popular is its open source rendition, BSD UNIX, which has seen many developments since the source code was first released. This means that BSD UNIX no longer exists but has instead diversified into a number of separate projects. Proprietary versions are also available, including Solaris, HP-UX, and AIX.
Upstart
Replacement for init, the software that effectively boots Ubuntu into a useable state whenever the computer is switched on or rebooted. However, Upstart goes beyond the design goals of init, and can stop and start various services (and also monitor them) on the fly while the system is up and running.
user
The way the operating system refers to anyone who accesses its resources. A user must first have a user account set up, effectively giving that user his or her own private space on the system. In addition to actual human users, an average Linux system has many other user accounts created to let programs and services go about their business. These are usually not seen by human users.
V
variable
A changeable value that stores a certain data type (such as a number, date, or string), remembering it for future reference by the system or script it is defined by. Variables defined by and for the Linux kernel are vital to it.
verbose
Command option that will cause it to return more-detailed output (or, in some cases, to return actual output if the command is otherwise “quiet”); usually specified by adding the -v command option.
VFAT
Virtual File Allocation Table; technical name of Microsoft’s FAT file system offered under Windows and also on removable storage devices such as flash memory cards.
vi
Arcane text editor and pseudo-shell beloved by UNIX aficionados that can be used for creation of text files or programs. Traditionally, UNIX users either love or hate vi; some prefer Emacs. Nowadays new and improved versions of vi are available, such as vim, used under Ubuntu.
W
Wine
Short for Wine Is Not an Emulator; software that re-creates the Windows application programming interface (API) layer within Linux and lets users run Windows programs.
workspace
X terminology referring to a GUI desktop.
X
X
Short for X Window; software that controls the display and input devices, thereby providing a software foundation on top of which Desktop managers like GNOME are able to run.
X11
Version 11 of the X software, currently in use on most desktop Linux systems.
XFree86 Project
Organization that creates X software. At one time, every distribution of Linux used XFree86 software, but most now use similar software from the X.org organization.
The service responsible for starting various network servers on the computer.
XMMS
Audio player program.
X.org
Organization that produces the X Window software and, in particular, a set of programs called X11. X11 is used on most modern distributions of Linux. It is backed by a number of UNIX and Linux industry leaders.
xterm
Simple program that allows you to run a shell under X. This program has the advantage of being available on most Linux systems that offer a GUI.
Xubuntu
Version of Ubuntu that utilizes the XFCE4 desktop environment instead of GNOME.