Apêndice 1. Glossário

conta

Em um sistema UNIX®, é a combinação de um nome, um diretório pessoal, uma senha e um shell que permite a um usuário conectar ao sistema.

alias

Um mecanismo utilizado em um shell para substituir uma string por outra antes de executar um comado. Você pode ver todos os aliases definidos na sessão atual digitando alias no prompt.

ACPI

Advanced Configuration and Power Interface. Serve para configurar e gerenciar o uso de energia do computador. Ao contrário do APM, que conta somente com a BIOS, o ACPI também conta com o sistema operacional, o que torna mais simples de ser operado pelo usuário. O ACPI também oferece recursos de gerenciamento de energia para servidores e estações de trabalho.

APM

Advanced Power Management. Utilizada por algumas BIOS para fazer a máquina entrar em modo de espera após um certo período de inatividade. Em laptops, o APM também é responsável por reportar o status da bateria e (se suportado) o tempo de carga que ainda resta na bateria. Porém, laptops novos utilizam o ACPI no lugar do APM.

Ver Também ACPI.

ARP

Address Resolution Protocol. Protocolo utilizado para mapear dinamicamente um endereço na internet para uma endereço físico (hardware) em uma rede local. O uso do protocolo é limitado a redes que possuem suporte a hardware broadcasting.

ASCII

American Standard Code for Information Interchange. O código padrão utilizado para o armazenamento de caracteres em um computador, incluindo caracteres de controle. Muitas codificações de 8-bit (como ISO 8859-1, normalmente o conjunto de caracteres padrão do Linux, a não ser que você tenha escolhido algo como UTF-8) possuem o ASCII como sua base.

Ver Também ISO 8859, UTF-8.

linguagem assembly

É a linguagem de programação mais próxima do computador, e é por isso que é conhecida como uma linguagem de programação de “baixo nível”. Assembly tem a vantagem da velocidade, já que programas assembly são escritos em termos de instruções pequenas do processador, além de não requerer “tradução” ao gerar executáveis. Sua desvantagem principal é a de que ele é dependente de processador (ou arquitetura), além de exigir bastante tempo para escrever sistemas muito complexos. Assim, assembly é a linguagem de programação mais rápida, mas também a menos portável entre as arquiteturas.

ATAPI

AT Attachment Packet Interface. Uma extensão à especificação ATA (Advanced Technology Attachment, mais conhecida como IDE, Integrated Drive Electronics) que fornece comandos extras para controlar drives de CD-ROM e de fita magnética. Controladores IDE equipados com esta extensão também são chamados de controladores EIDE (Enhanced IDE).

Ver Também IDE.

ATM

Acrônimo para Asynchronous Transfer Mode. Uma rede ATM empacota os dados em blocos de tamanho padrão (53 bytes: 48 para os dados e 5 para o cabeçalho) que pode ser transportado eficientemente de uma ponta a outra.

atômico

Um conjunto de operações é chamado de atômico quando todas elas são executadas de uma só vez. Ou todas as operações obtém sucesso, ou nenhuma delas é levada em consideração. Pode ser utilizado para operações essenciais ou muito simples, como a soma de números integrais.

segundo plano

No contexto do shell, um processo é executado em segundo plano se você pode continuar a executar outros comandos no shell enquanto ele continua a ser executado. É o contrário do processo em primeiro plano.

Ver Também job, foreground.

backup

Um meio de salvar informações importantes em uma mídia e local mais seguros. Os backups devem ser realizados regularmente, especialmente para as informações mais críticas e arquivos de configuração (os diretórios mais importantes para se fazer backup são o /etc, /home e /usr/local). Muitas pessoas utilizam o tar com o gzip ou bzip2 para fazer o backup de diretórios e arquivos. Você também pode usar programas como o dump e restore, assim como qualquer outra solução para backup comercial ou livre.

processamento em lote

Um modo de processamento onde tarefas ou instruções que são enviadas ao CPU são executadas seqüencialmente até que todas sejam processadas.

beep

O pequeno barulho que o speaker do computador emite para lhe avisar de alguma situação ambígua, como por exemplo quando você está usando a completação de comandos pelo shell e há mais de uma opção possível para completar. Podem haver outros programas que utilizarão o beep para lhe avisar alguma situação específica.

beta testing

O nome dado ao processo de teste da versão beta de um programa. Programas normalmente são lançados em versões “alpha”, “beta” e “release candidate” para que testes sejam realizados antes da versão final.

binário

No contexto de programação, binários são códigos compilados, executáveis.

bit

Quer dizer BInary digiT. Um único bit que pode receber os valores 0 ou 1, porque o cálculo é feito em base binária. É a unidade mais básica de informação digital.

aquivos de bloco

Arquivos cujos conteúdos são armazenados em buffers. Todas as operações de leitura/escrita são realizadas através de buffers, que permitem leitura assíncrona de dados e escrita ao hardware suportado, evitando assim que acesso desnecessário seja feito ao disco se os dados já estiverem armazenados em um buffer.

Ver Também buffer, buffer cache, arquivos de caractere.

boot

O procedimento executado assim que o computador é ligado, onde os periféricos são reconhecidos seqüencialmente e o sistema operacional é carregado na memória.

disco de boot

Um disco inicializável contendo o código necessário para carregar um sistema operacional a partir do disco rígido.

gerenciador de inicialização

É o programa que inicia o sistema operacional. Muitos gerenciadores de inicialização dão a oportunidade de carregar mais de um sistema operacional, permitindo que você faça a sua escolha em um menu. Gerenciadores de inicialização como o GRUB e LILO são populares por sua utilidade em sistemas multi ou dual-boot.

BSD

Berkeley Software Distribution. Uma variante do UNIX® desenvolvido pelo departamento de informática da Universidade de Berkeley. Esta versão sempre foi considerada a mais avançada tecnicamente. Trouxe muitas inovações ao mundo da informática e, em particular, ao UNIX®.

buffer

Uma pequena porção de memória com tamanho fixo, que pode ser associada a um arquivo de bloco, uma tabela de sistema, um processo e etc. O buffer cache mantém a coerência de todos os buffers.

Ver Também buffer cache.

buffer cache

Uma parte crucial do kernel de um sistema operacional, ele mantém todos os buffers atualizados, diminuindo o cache quando necessário, limpando buffers que não estão mais sendo usados e etc.

Ver Também buffer.

bug

Comportamento ilógico ou incoerente de um programa em um caso especial, ou um comportamento que não segue a documentação ou padrões aceitos pelo programa. Novas funcionalidades, normalmente, adicionam novos bugs ao programa. Historicamente, este termo vem dos tempos dos cartões perfurados: um inseto (bug em inglês) caiu em um buraco do cartão e, como conseqüência, o programa agiu de maneira errada. O Almirante Grace Hopper, quando descobriu o motivo, disse “É um inseto!” (It's a bug!, em inglês), e desde então o termo continuou a ser utilizado. Esta é apenas uma das muitas histórias existentes para a explicação do termo bug.

byte

Uma seqüência de, normalmente, oito bits consecutivos, que quando convertidos para a base decimal resultam em um inteiro entre 0 e 255. Um byte é sempre “atômico” para o sistema, sendo a menor unidade endereçável.

Ver Também bit.

caso

Quando falamos em strings, o caso é a diferença entre letras minúsculas e maiúsculas.

CHAP

Challenge-Handshake Authentication Protocol: Um protocolo utilizado por provedores de internet para autenticar seus clientes. Desta forma, um valor é enviado para o cliente (a máquina que está fazendo a conexão), a qual costuma calcular um hash baseado neste valor. O cliente envia o hash para o servidor fazer uma comparação. Este método de autenticação é diferente do PAP, em que ele faz uma autenticação de tempo em tempo após a autenticação inicial.

Ver Também PAP.

arquivos de caractere

Arquivos cujo conteúdo não são armazenados em buffers. Quando associado a dispositivos físicos, toda a entrada/saída nestes dispositivos é realizada imediatamente. Alguns dispositivos especiais de caractere são criados pelo sistema operacional (/dev/zero, /dev/null e outros). Eles correspondem a fluxo de dados.

Ver Também aquivos de bloco.

CIFS

Common Internet File System. O sucessor do sistema de arquivos SMB, utilizado em sistemas DOS.

Ver Também SMB.

cliente

Um programa ou computador que conecta esporadicamente, por um certo período de tempo, a outro programa ou computador para lhe passar comandos ou obter informações. No caso de sistemas peer to peer como SLIP ou PPP, o cliente é definido como a ponta que iniciará a conexão, e a ponta remota que recebe a conexão é definida como servidor. É um dos componentes de um sistema cliente/servidor.

Ver Também server.

sistema cliente/servidor

Sistema ou protocolo que consiste em um servidor e um ou mais clientes.

linha de comando

É fornecida por um shell e permite que o usuário entre com comandos diretamente.

modo de comando

Sob o Vi ou algum de seus clones, é o estado do programa em que quando pressionamos uma tecla nenhum caractere é inserido no arquivo que está sendo editado, mas ao invés disto realiza uma ação específica da tecla (a não ser que o clone possua comandos que podem ser mapeados novamente, e que você tenha personalizado esta configuração). Você pode sair deste modo digitando um dos comandos que retornam ao modo de inserção: i, I, a, A, s, S, o, O, c, C, ...

compilação

É o processo de transformar o código fonte, que pode ser entendido por humanos (com algum treino) e são escritos em alguma linguagem de programação (C, por exemplo), em um arquivo binário que pode ser entendido e executado pela máquina.

completação

A habilidade de um shell em expandir automaticamente uma substring para um nome de arquivo, nome de usuário ou outro item que combine com ela.

compressão

Uma forma de diminuir o tamanho de arquivos ou o número de caracteres enviados através de um link de comunicação. Entre os programas de compressão de arquivos estão o compress, zip, gzip, e bzip2.

console

Este é o nome dado ao que costumava ser chamado de terminais. Eles eram as máquinas (uma tela e um teclado) conectadas a um mainframe central. Nos PCs, o terminal físico é o teclado e a tela.

Ver Também virtual console.

cookies

Arquivos temporários escritos no disco rígido local por um servidor web remoto. Ele permite que o servidor “lembre” as preferências do usuário quando este usuário conectar novamente.

datagram

Um datagram é um pacote discreto de dados e cabeçalhos que contém endereços. É a unidade básica de transmissão através de uma rede IP. Você também pode ter ouvido falar dele como um “pacote de informação”.

dependências

Os estágios de compilação que precisam ser satisfeitos antes de prosseguir para outros estágios para compilar com sucesso um programa. Este termo também é utilizado quando um conjunto de programas que você deseja instalar depende de outros programas que podem ou não estar instalados em seu sistema. Neste caso uma mensagem lhe informará que será necessário “satisfazer as dependências” para continuar a instalação.

desktop

Se você estiver utilizando o X Window System, o desktop é o lugar na tela onde você trabalha e onde são exibidos os ícones e janelas.

Ver Também virtual desktops.

DHCP

Dynamic Host Configuration Protocol. Um protocolo desenvolvido para máquinas em uma rede local que possibilita aos clientes obterem dinamicamente um endereço IP e outras configurações de rede a partir de um servidor.

diretório

Parte da estrutura do sistema de arquivos. Arquivos ou outros diretórios podem ser armazenados em um diretório. Às vezes há subdiretórios dentro de um diretório, e esta estrutura é conhecida como árvore de diretórios. Se você quer ver o que tem dentro de outro diretório, você tem que listá-lo ou acessá-lo. Diretórios seguem as mesmas restrições que arquivos, embora as permissões tenham significados diferentes. Os diretórios especiais . e .. referem-se ao próprio diretório e ao diretório pai (um nível acima), respectivamente. Em um ambiente gráfico os diretórios são conhecidos como pastas.

valores discretos

São valores que não são contínuos, isto é, existe algum tipo de “espaço” entre os valores consecutivos.

distribuição

Uma distribuição é feita com o kernel do Linux e utilitários, assim como programas de instalação, programas de terceiros e, às vezes, software proprietário.

DLCI

O DLCI - Data Link Connection Identifier - é utilizado para identificar uma única conexão virtual ponto-a-ponto através de uma rede Frame Relay. Os DLCIs são normalmente atribuídos ao provedor da rede Frame Relay.

DMA

Direct Memory Access. Uma facilidade utilizada na arquitetura do PC que permite a um periférico ler ou escrever na memória principal sem a ajuda do CPU. Periféricos PCI utilizam o barramento e não precisam da DMA.

DNS

Domain Name System. Mecanismo de nome e endereço utilizado na internet, que lhe permite mapear um domínio para um endereço de IP, permitindo que você acesse um site através do domínio, sem ter que saber o endereço IP do site. O DNS também permite pesquisa reversa, ou seja, obter o nome através do endereço IP da máquina.

DPMS

Display Power Management System. Protocolo utilizado por todos os monitores modernos para gerenciar o controle de uso de energia. Monitores que possuem esta tecnlogia são chamados de monitores verdes (“green monitors”).

echo

Ocorre quando os caracteres que você digita são exibidos na tela, como quando informamos o nome de usuário durante a sessão de login, por exemplo. Alguns programas também podem mascarar o que digitamos por questões de segurança, como por exemplo quando informamos uma senha e ela é substituída por * em cada caractere que digitamos.

editor

Is a term typically used for programs which edit text files (aka text editor). The most well-known GNU/Linux editors are the GNU Emacs (Emacs) editor and the UNIX® editor Vi.

ELF

Executable and Linking Format. This is the binary format used by most GNU/Linux distributions.

email

Stands for Electronic Mail. This is a way to send messages electronically. Similar to regular mail (aka snail mail), email needs a destination and sender address to be sent properly. The sender must have an address like “sender@senders.domain” and the recipient must have an address like “recipient@recipients.domain.” Email is a very fast method of communication and typically only takes a few minutes to reach anyone, regardless of where in the world they are located. In order to write email, you need an email client such as pine or mutt which are text-mode clients, or GUI clients such as KMail.

environment

Is the execution context of a process. It includes all the information that the operating system needs to manage the process and what the processor needs to execute the process properly.

Ver Também process.

environment variables

A part of a process' environment. Environment variables are directly viewable from the shell.

Ver Também process.

escape

In the shell context, is the action of surrounding a string with quotes to prevent the shell from interpreting that string. For example, when you need to use spaces in a command line and then pipe the results to some other command you have to put the first command between quotes or precede the spaces with a \ (“escape” the command) otherwise the shell will interpret it incorrectly and your command won't work as expected.

ext2

Short for the “Extended 2 file system”. This is GNU/Linux's native file system and has the characteristics of any UNIX® file system: support for special files (character devices, symbolic links, etc), file permissions and ownership, and other features.

FAQ

Frequently Asked Questions. A document containing a series of questions and answers about a specific topic. Historically, FAQs appeared in newsgroups, but this sort of document now appears on various web sites, and even commercial products have FAQs. Generally, they are very good sources of information.

FAT

File Allocation Table. File system used by DOS and Windows®.

FDDI

Fiber Distributed Digital Interface. A high-speed network physical layer, which uses optical fiber for communication instead of wire. Mostly used on large networks, mainly because of its price. It is rarely seen as a means of connection between a PC and a network switch.

FHS

File system Hierarchy Standard. A document containing guidelines for a coherent file tree organisation on UNIX® systems. Mandriva Linux complies with this standard in most aspects.

FIFO

First In, First Out. A data structure or hardware buffer where items are taken out in the order they were put in. UNIX® pipes are the most common examples of FIFOs.

filesystem

Scheme used to store files on physical media (hard drive, floppy, etc.) in a consistent manner. Examples of file systems are FAT, GNU/Linux' ext2fs, ISO9660 (used by CD-ROMs) and so on. An example of a virtual filesystem is the /proc filesystem.

firewall

A machine or a dedicated piece of hardware which in the topology of a local network is the single connection point to the outside network, and which filters and controls the activity on some ports, or makes sure that only some specific interfaces may have access to, or can be accessed from, the outside world.

flag

Is an indicator (usually a bit) that is used to signal some condition to a program. For example, a filesystem has, among others, a flag indicating if it has to be dumped in a backup, so when the flag is active the filesystem gets backed up, and when it's inactive it doesn't.

focus

The state for a window to receive keyboard events (such as key-presses, key-releases and mouse clicks) unless they are trapped by the window manager.

foreground

In shell context, the process in the foreground is the one that is currently running and has keyboard and screen control. You have to wait for such a process to finish in order to be able to type commands again.

Ver Também job, segundo plano.

Frame Relay

Frame Relay is a network technology ideally suited to carrying traffic which is of a bursty or sporadic nature. Network costs are reduced by having many Frame Relay customers sharing the same network capacity and relying on them wanting to make use of the network at slightly different times.

framebuffer

Projection of a video card's RAM into the machine's address space. This allows applications to access the video RAM without the chore of having to talk to the card. All high-end graphical workstations use frame buffers.

FTP

File Transfer Protocol. This is the standard Internet protocol used to transfer files from one machine to another.

full-screen

This term is used to refer to applications that take up the entire visible area of your display.

gateway

Machine or device giving a local network access to an outside network.

GFDL

The GNU Free Documentation License. The license which applies to all Mandriva Linux documentation.

GIF

Graphics Interchange Format. An image file format, widely used on the web. GIF images may be compressed or animated. Due to copyright problems it is a bad idea to use them, the recommended solution is to replace them as much as possible by the PNG format.

Ver Também PNG.

globbing

In the shell, the ability to group a certain set of filenames with a globbing pattern.

Ver Também globbing pattern.

globbing pattern

A string made of normal characters and special characters. Special characters are interpreted and expanded by the shell.

GNU

GNU's Not Unix. The GNU project was initiated by Richard Stallman at the beginning of the 1980s, and aimed at developing a free operating system (“free” as in “free speech”). Currently, all tools are there, except... the kernel. The GNU project kernel, Hurd, is not rock solid yet. Linux borrows, among others, two things from GNU: its C compiler, gcc, and its license, the GPL.

Ver Também GPL.

GPL

General Public License. The license of the GNU/Linux kernel, it goes the opposite way to all proprietary licenses in that it applies no restrictions as to copying, modifying and redistributing the software, as long as the source code is made available. The only restriction is that the persons to whom you redistribute it must also benefit from the same rights.

GUI

Graphical User Interface. Interface to a computer consisting of windows with menus, buttons, icons and so on. A great majority of users prefer a GUI to a CLI (Command Line Interface) for ease of use, even though the latter is far more versatile.

guru

An expert. Used to qualify someone particularly skilled, but also of valuable help for others.

hardware address

This is a number which uniquely identifies a host in a physical network at the media access layer. Examples of this are Ethernet Addresses and AX.25 Addresses.

hidden file

Is a file which can't be “seen” when doing a ls command without options. Hidden files' filenames begin with a . and are used to store the user's personal preferences and configurations for the different programs he uses. For example, bash's command history is saved into .bash_history, a hidden file.

home directory

Often abbreviated as “home”, this is the name for the personal directory of a given user.

Ver Também conta.

host

Refers to a computer and is commonly used when talking about computers which are connected to a network.

HTML

HyperText Markup Language. The language used to create web documents.

HTTP

HyperText Transfer Protocol. The protocol used to connect to web sites and retrieve HTML documents or files.

icon

Is a little drawing (normally sized 16x16, 32x32, 48x48 and sometimes 64x 64 pixels) which in a graphical environment represents a document, a file or a program.

IDE

Integrated Drive Electronics. The most widely used bus on today's PCs for hard disks. An IDE bus may contain up to two devices, and the speed of the bus is limited by the device on the bus with the slowest command queue (and not the slowest transfer rate!).

Ver Também ATAPI, SATA, S-ATA.

IMAP

Internet Message Access Protocol. A protocol which allows you to access your email messages on a remote server, without the need to transfer them locally first; as opposed to the POP mail retrieval protocol.

Ver Também POP.

inode

Entry point leading to the contents of a file on a UNIX®-like filesystem. An inode is identified in a unique way with a number, and contains meta-information about the file it refers to, such as its access times, its type, its size, but not its name!

insert mode

Under Vi or any of its clones, it is the state of the program in which pressing a key will insert that character in the file being edited (except pathological cases like the completion of an abbreviation, right justify at the end of the line, ...). One gets out of it pressing the Esc key, (or Ctrl-[).

Internet

Is a huge network which connects computers around the world.

IP address

Is a numeric address consisting (in version 4, also called IPv4) of four parts which identifies your computer on a network. IP addresses are structured in a hierarchical manner, with top level and national domains, domains, sub-domains and each machine's personal address. An IP address will look something like 192.168.0.1. A machine's personal address can be one of two types: static or dynamic. Static IP addresses are addresses which never change, they are permanently assigned. Dynamic IP addresses mean that an IP address will change with each new connection to the network. Most home users typically have dynamic IP addresses while most corporate users typically have static IP addresses.

IP masquerading

This is a technique where a firewall is used to hide your computer's true IP address from the outside. Typically, any outside network connections you make through the firewall will inherit the firewall's IP address. This is useful in situations where you may have a fast Internet connection with only one IP address but wish to use more than one computer on your internal network.

IRC

Internet Relay Chat. One of the few Internet standards for live speech. It allows for channel creation, private talks and file exchange. It also allows servers to connect to each other, which is why several IRC networks exist today: Undernet, DALnet, EFnet to name a few.

IRC channels

Are the “places” inside IRC servers where you can chat with other people. Channels are created in IRC servers and users join those channels so they can communicate with each other. Messages written on one channel are only visible to the people connected to that channel. Two or more users can create a “private” channel so they don't get disturbed by other users. Channel names begin with a #.

ISA

Industry Standard Architecture. The very first bus used on PCs, it is slowly being abandoned in favour of the PCI bus. ISA is still commonly found on SCSI cards supplied with scanners, CD writers and some other older hardware.

ISDN

Integrated Services Digital Network. A set of communication standards for voice, digital network services and video. It has been designed to eventually replace the current phone system, known as PSTN (Public Switched Telephone Network) or POTS (Plain Old Telephone Service). ISDN is known as a circuit switched data network.

ISO

International Standards Organization. A group of companies, consultants, universities and other sources which enumerates standards in various disciplines, including computing. The papers describing standards are numbered. The standard number iso9660, for example, describes the file system used on CD-ROMs.

ISO 8859

The ISO 8859 standard includes several 8-bit extensions to the ASCII character set. Especially important is ISO 8859-1, the “Latin Alphabet No. 1”, which has become widely implemented and may already be seen as the de facto standard ASCII replacement.

ISO 8859-1 supports the following languages: Afrikaans, Basque, Catalan, Danish, Dutch, English, Faroese, Finnish, French, Galician, German, Icelandic, Irish, Italian, Norwegian, Portuguese, Scottish, Spanish, and Swedish.

Note that the ISO 8859-1 characters are also the first 256 characters of ISO 10646 (Unicode). However, it lacks the EURO symbol and does not fully cover Finnish and French. ISO 8859-15 is a modification of ISO 8859-1 to covers these needs.

Ver Também ASCII, UTF-8.

ISP

Internet Service Provider. A company which sells Internet access to its customers, either over telephone lines or high-bandwidth circuits such as dedicated T-1 circuits, DSL or cable.

JPEG

Joint Photographic Experts Group. Another very common image file format. JPEG is mostly suited for compressing real-world scenes, and does not work very well on non-realistic images.

job

In a shell context, a job is a process running in the background. You can have several jobs running in the same shell and control each job independently.

Ver Também foreground, segundo plano.

journaling

Journaling adds robustness to a file system, by making it transactional. Thus, instead of physically writing data at the moment it's asked for, a journal of the writes is kept, and data is written “in a block” at a later time which has also a great impact on performance and on the time needed to analyse and fix the file system, if needed.

kernel

Is the core of the operating system. The kernel is responsible for allocating resources and separating processes from each other. It handles all of the low-level operations which allow programs to talk directly to the hardware on your computer, manages the buffer cache and so on.

kill ring

Under Emacs, it is the set of text areas cut or copied since the editor was started. The text areas may be recalled to be inserted again, and the structure is ring-like.

LAN

Local Area Network. Generic name given to a network of machines connected to the same physical wiring in a reduced geographical area, such as the same office or building.

Ver Também WAN.

launch

Is the action of invoking, or starting, a program.

library

Is a collection of procedures and functions in binary form to be used by programmers in their programs (as long as the library's license allows them to do so). The program in charge of loading shared libraries at run time is called the dynamic linker.

link

Reference to an inode in a directory, therefore giving a (file) name to the inode. Examples of inodes which don't have a link (and hence have no name) are: anonymous pipes (as used by the shell), sockets (aka network connections), network devices and so on.

linkage

The last stage of the compilation process, consisting of linking together all object files in order to produce an executable file, and matching unresolved symbols with dynamic libraries (unless a static linkage has been requested, in which case the code of these symbols will be included in the executable).

Linux

Is a UNIX®-like operating system which runs on a variety of different computers, and is free for anyone to use and modify. Linux (the kernel) was written by Linus Torvalds.

login

Connection name for a user on a UNIX® system, and the action to connect.

lookup table

Is a table which stores corresponding codes (or tags) and their meanings. It is often a data file used by a program to get further information about a particular item.

For example, HardDrake uses such a table to store a manufacturer's product codes and associated configuration information. This is one line from that table, giving information about item CTL0001

"CTL0001"       "sb"    "Creative Labs|SB16"    "sound" "HAS_OPL3|HAS_MPU401|HAS_DMA16|HAS_JOYSTICK"

loopback

Virtual network interface of a machine to itself, allowing the running programs not to have to take into account the special case where two network entities are in fact the same machine.

major

Number specific to the device class.

manual page

Small documents containing the definitions of a command and its usage, to be consulted with the man command. The first thing one should (learn how to) read when learning about a command one isn't familiar with.

MBR

Master Boot Record. Name given to the first sector of a bootable hard drive. The MBR contains the code used to load the operating system into memory or a bootloader (such as LILO), and the partition table of that hard drive.

MIME

Multipurpose Internet Mail Extensions. A string of the form type/subtype describing the contents of a file attached in an e-mail. This allows MIME-aware mail clients to define actions depending on the type of the file.

minor

Number identifying the specific device we are talking about.

MPEG

Moving Picture Experts Group. An ISO committee which generates standards for video and audio compression. MPEG is also the name of their algorithms. Unfortunately, the license for this format is very restrictive, and as a consequence there are still no Open Source MPEG players...

mount point

Is the place or directory where a partition or another device is attached to the GNU/Linux filesystem. For example, your CD-ROM is mounted in the /mnt/cdrom directory, from where you can explore the contents of any mounted CDs.

mounted

A device is mounted when it is attached to the GNU/Linux filesystem. When you mount a device you can browse its contents. This term is partly obsolete due to the “supermount” feature, so users do not need to manually mount removable media.

Ver Também mount point.

MSS

The Maximum Segment Size is the largest quantity of data which can be transmitted at one time across an interface. If you want to prevent local fragmentation MSS would equal the MTU IP header.

MTU

The Maximum Transmission Unit is a parameter which determines the size of the largest datagram which can be transmitted by an IP interface without it needing to be broken down into smaller units. The MTU should be larger than the largest datagram you wish to transmit un-fragmented. Note, this only prevents fragmentation locally, some other link in the path may have a smaller MTU and the datagram will be fragmented there. Typical values are 1500 bytes for an Ethernet interface, or 576 bytes for a PPP interface.

multitasking

The ability of an operating system to share CPU time between several processes. At a low level, this is also known as multiprogramming. Switching from one process to another requires that all the current process context be saved and restored when this process runs again. This operation is called a context switch, and is done several times per second, thereby making it fast enough so that a user has the illusion that the operating system runs several applications at the same time. There are two types of multitasking: in preemptive multitasking the operating system is responsible for taking away the CPU and passing it to another process; cooperative multitasking is where the process itself gives back the CPU. The first variant, used by GNU/Linux, is obviously the better choice because no program can consume the entire CPU time and block other processes. The policy to select which process should be run, depending on several parameters, is called scheduling.

multiuser

Is used to describe an operating system which allows multiple users to log into and use the system at the exact same time, each user being able to do their own work independent of other users. A multitasking operating system is required to provide multiuser support. GNU/Linux is both a multitasking and multiuser operating system, as is any UNIX® system for that matter.

named pipe

A UNIX® pipe which is linked, as opposed to pipes used in shells.

Ver Também pipe, link.

naming

A word commonly used in computing for a method to identify objects. You will often hear of “naming conventions” for files, functions in a program and so on.

NCP

NetWare Core Protocol. A protocol defined by Novell to access Novell NetWare™ file and print services.

NFS

Network File System. A network file system created by Sun Microsystems in order to share files across a network in a transparent way.

newsgroups

Discussion and news areas which can be accessed by a news or USENET client to read and write messages specific to the topic of the newsgroup. For example, the newsgroup alt.os.linux.mandrake is an alternate newsgroup (alt) dealing with the Operating System (OS) GNU/Linux (linux), and specifically, Mandriva Linux (mandrake). Newsgroups are broken down in this fashion to make it easier to search for a particular topic.

NIC

Network Interface Controller. An adapter installed in a computer which provides a physical connection to a network, such as an Ethernet card.

NIS

Network Information System. NIS was also known as “Yellow Pages”, but British Telecom holds a copyright on this name. NIS is a protocol designed by Sun Microsystems in order to share common information across a NIS domain, which may consist of an entire LAN, or just a part of it. It can export password databases, service databases, groups information and more.

null, character

The character or byte number 0. It is used to mark the end of a string.

object code

Is the code generated by the compilation process to be linked with other object codes and libraries to form an executable file. Object code is machine readable.

Ver Também compilação, linkage.

on the fly

Something is said to be done “on the fly” when it's done along with something else, without you noticing it or explicitly asking for it.

open source

Is the name given to free source code of a program that is made available to the development community and public at large. The theory behind this is that allowing source code to be used and modified by a broader group of programmers will ultimately produce a more useful product for everyone. Some popular open source programs include Apache, sendmail and GNU/Linux.

operating system

Is the interface between the applications and the underlying hardware. The tasks for any operating system are primarily to manage all of the machine specific resources. On a GNU/Linux system, this is done by the kernel and loadable modules. Other well-known operating systems include Amiga®OS, Mac OS®, FreeBSD®, OS/2®, UNIX®, and Windows® in all its variants.

owner

In the context of users and their files, the owner of a file is the user who created that file.

owner group

In the context of groups and their files, the owner group of a file is the group to which the user who created that file belongs.

PAP

Password Authentication Protocol. A protocol used by many ISPs to authenticate their clients. In this scheme, the client (you) sends an identifier/password pair to the server, but none of the information is encrypted. CHAP is a more secure, and thus preferred, authentication protocol.

Ver Também CHAP.

pager

A program which displays a text file one screen at a time, making it easy to move back and forth and search for strings in this file. We suggest you to use less.

password

Is a secret word or combination of words or letters which is used to secure something. Passwords are used in conjunction with user logins to multi-user operating systems, web sites, FTP sites, and so forth. Passwords should be hard-to-guess phrases or alphanumeric combinations, and should never be based on common dictionary words. Passwords ensure that other people cannot log into a computer or site with your account.

patch, to patch

A file containing a list of corrections to issue to source code in order to add new features, to remove bugs, or to modify it according to one's wishes and needs. The action consisting of the application of these corrections to the archive of source code (aka “patching”).

path

Is an assignment for files and directories to the filesystem. The different layers of a path are separated by the "slash" or '/' character. There are two types of paths on GNU/Linux systems. The relative path is the position of a file or directory in relation to the current directory. The absolute (or full) path is the position of a file or directory in relation to the root directory.

PCI

Peripheral Component Interconnect. A bus created by Intel which today is the standard bus for PC and other architectures. It is the successor to ISA, and it offers numerous services: device identification, configuration information, IRQ sharing, bus mastering and more.

PCMCIA

Personal Computer Memory Card International Association. More and more commonly called “PC Card” for simplicity reasons, this is the standard for external cards attached to a laptop: modems, hard disks, memory cards, Ethernet cards, and more. The acronym is sometimes humorously expanded to People Cannot Memorize Computer Industry Acronyms...

pipe

A special UNIX® file type. One program writes data into the pipe, and another program reads the data from the other end. UNIX® pipes are FIFOs, so the data is read at the other end in the order it was sent. Very widely used with the shell. See also named pipe.

pixmap

Is an acronym for “pixel map”. It's another way of referring to bitmap images.

plugin

Add-on program used to display or play some multimedia content found on a web document. It can usually be easily downloaded if your browser is not yet able to display or play that kind of information.

PNG

Portable Network Graphics. Image file format created mainly for web use, it has been designed as a patent-free replacement for GIF and also has some additional features.

PnP

Plug'N'Play. First an add-on for ISA in order to add configuration information for devices, it has become a more widespread term which groups all devices able to report their configuration parameters. All PCI devices are Plug'N'Play.

POP

Post Office Protocol. One common protocol used for retrieving mail from an ISP. See IMAP for an example of another remote-access mail protocol.

Ver Também IMAP.

porting

One of two ways to run a program on a system it was not originally intended for. For example, to be able to run a Windows®-native program under GNU/Linux (natively), it must first be ported to GNU/Linux.

PPP

Point to Point Protocol. This is the protocol used to send data over serial lines. It is commonly used to send IP packets to the Internet, but it can also be used with other protocols such as Novell's IPX protocol.

precedence

Dictates the order of evaluation of operands in an expression. For example: If you have 4 + 3 * 2 you get 10 as the result, since the multiplication has higher precedence than the addition. If you want to evaluate the addition first, then you have to add parenthesis like this: (4 + 3) * 2. When you do this, you'll get 14 as the result since the parenthesis have higher precedence than the addition and the multiplication, so the operations in parenthesis get evaluated first.

preprocessors

Are compilation directives which instruct the compiler to replace those directives for code in the programming language used in the source file. Examples of C 's preprocessors are #include, #define, etc.

process

In the operating system context, a process is an instance of a program being executed along with its environment.

prompt

In a shell, this is the string before the cursor. When you see it, you can type your commands.

protocol

Protocols organise the communications between different machines across a network, either using hardware or software. They define the format of transferred data, whether one machine controls another, etc. Many well-known protocols include HTTP, FTP, TCP, and UDP.

proxy

A machine which sits between a network and the Internet, whose role is to speed up data transfers for the most widely used protocols (for example, HTTP and FTP). It maintains a cache of previous requests, so that a machine which makes a request for something which is already cached will receive it quickly, because it will get the information from the local cache. Proxies are very useful on low bandwidth networks (such as modem connections). Sometimes the proxy is the only machine able to access outside the network.

pull-down menu

Is a menu that is “rolled” with a button in some of its corners. When you press that button, the menu “unrolls” itself, showing you the full menu.

quota

Is a method of restricting disk usage and put limits for users. Administrators can restrict the size of home directories for a user by setting quota limits on specific file systems.

RAID

Redundant Array of Independent Disks. A project initiated at the computing science department of Berkeley University, in which the storage of data is spread across an array of disks using different schemes. At first, this was implemented using low-cost, older, drives, which is why the acronym originally stood for Redundant Array of Inexpensive Disks.

RAM

Random Access Memory. Term used to identify a computer's main memory. The “Random” here means that any part of the memory may be directly accessed.

read-only mode

For a file means that the file cannot be written to. You can read its contents but you can't modify them.

Ver Também read-write mode.

read-write mode

For a file, it means that the file can be written to. You can read its contents and modify them.

Ver Também read-only mode.

regular expression

A powerful theoretical tool which is used to search and match text strings. It lets one specify patterns these strings must obey. Many UNIX® utilities use it: sed, awk, grep, perl and others.

RFC

Request For Comments. RFCs are the official Internet standard documents, published by the IETF (Internet Engineering Task Force). They describe all protocols, their usage, their requirements and so on. When you want to learn how a protocol works, pick up the corresponding RFC.

root

Is the superuser of any UNIX® system. Typically root (aka the system administrator) is the person responsible for maintaining and supervising the UNIX® system. This person also has complete access to everything on the system.

root directory

This is the top level directory of a filesystem. This directory has no parent directory, thus '..' for root points back to itself. The root directory is written as '/'.

root filesystem

This is the top level filesystem. This is the filesystem where GNU/Linux mounts its root directory tree. It is necessary for the root filesystem to reside in a partition of its own, as it is the basis for the whole system. It contains the root directory.

route

Is the path which your datagrams take through the network to reach their destination. It is the path between one machine and another in a network.

RPM

RPM Package Manager. A packaging format developed by Red Hat in order to create software packages, it is used in many GNU/Linux distributions, including Mandriva Linux.

run level

Is a configuration of the system software which only allows certain selected processes to exist. Allowed processes are defined, for each runlevel, in the file /etc/inittab. Usually, there are seven defined runlevels: 0, 1, 2, 3, 4, 5, 6 and switching between them can only be achieved by a privileged user by means of executing the commands init and telinit.

SATA, S-ATA

Serial ATA. The successor to the ATA specification. First generation SATA has a bandwidth of 1.5Gbps, but the serial link and underlying technologies allow for much greater bandwidths, while parallel ATA has reached its practical limits with UDMA133.

Ver Também ATAPI, IDE.

script

shell scripts are sequences of commands to be executed as if they were sequentially entered in the console. shell scripts are UNIX®'s (somewhat) equivalent of DOS batch files.

SCSI

Small Computers System Interface. A bus with a high throughput designed to allow for several types of peripherals to be connected to it. Unlike IDE, a SCSI bus is not limited by the speed at which the peripherals accept commands. Only high-end machines integrate a SCSI bus directly on the motherboard, therefore most PCs need add-on cards.

security levels

Mandriva Linux's unique feature which allows you to set different levels of restriction according to how secure you want to make your system. There are 6 predefined levels ranging from 0 to 5, where 5 is the tightest security. You can also define your own security level.

segmentation fault

A segmentation fault occurs when a program tries to access memory that is not allocated to it. This generally causes the program to stop immediately.

server

A program or computer which provides a feature or service and awaits the connections from clients to execute their orders or give them the information they ask for. In the case of peer to peer systems such as SLIP or PPP, the server is taken to be the end of the link that is called and the end calling is taken to be the client. It is one of the components of a client/ server system.

Ver Também cliente, sistema cliente/servidor.

shadow passwords

A password management suite on UNIX® systems in which the file containing the encrypted passwords is not world-readable, unlike that usually found with a normal password system. It also offers other features such as password aging.

shell

The shell is the basic interface to the operating system kernel and provides the command line where users enter commands to run programs and system commands. All shells provide a scripting language which can be used to automate tasks or simplify often-used complex tasks. These shell scripts are similar to batch files from the DOS operating system, but are much more powerful. Some example shells are bash, sh, and tcsh.

single user

Is used to describe a state of an operating system, or even an operating system itself, which only allows a single user to log into and use the system at any time.

site dependent

Means that the information used by programs such as imake and make to compile some source file depends on the site, the computer architecture, the computer's installed libraries, and so on.

SMB

Server Message Block. Protocol used by Windows® machines for file and printer sharing across a network.

Ver Também CIFS.

SMTP

Simple Mail Transfer Protocol. This is the common protocol for transferring email. Mail Transfer Agents such as sendmail or postfix use SMTP. They are sometimes called SMTP servers.

socket

File type corresponding to any network connection.

soft links

Ver symbolic links.

standard error

The file descriptor number 2, opened by every process, used by convention as the file descriptor to which the process writes errors. It is usually the computer's screen.

Ver Também standard input, standard output.

standard input

The file descriptor number 0, opened by every process, used by convention as the file descriptor from which the process receives data. It is usually the computer's keyboard.

Ver Também standard error, standard output.

standard output

The file descriptor number 1, opened by every process, used by convention as the file descriptor in which the process prints its output. It is usually the computer's screen.

Ver Também standard error, standard input.

streamer

Is a device which takes “streams” (not interrupted or divided in shorter chunks) of characters as its input. A typical streamer is a tape drive.

SVGA

Super Video Graphics Array. The video display standard defined by VESA for the PC architecture. The resolution was at first 800x 600 x 16 colours, quickly extended to 1024x768 x 16 colours, and beyond.

switch

Switches are used to change the behaviour of programs, and are also called command-line options or arguments. To determine if a program has optional switches which may be used, read the man pages or try to pass the --help switch to the program (i.e.. program --help).

symbolic links

Are special files, containing nothing but a string which references another file. Any access to them is the same as accessing the file whose name is the referenced string, which may or may not exist, and the path to which can be given in a relative or an absolute way.

target

Is the object of compilation, i.e. the binary file to be generated by the compiler.

TCP

Transmission Control Protocol. This is the most common reliable protocol which uses IP to transfer network packets. TCP adds the necessary checks on top of IP to make sure that packets are delivered. Unlike UDP, TCP works in connected mode, which means that two machines must establish a connection before exchanging data.

telnet

Creates a connection to a remote host and allows you to log into the machine, provided you have an account. Telnet is the most widely-used method of remote logins, however there are better and more secure alternatives, such as ssh.

theme-able

A graphical application is theme-able if it is able to change its appearance in real time. Many window managers are theme-able.

TLDP

The Linux Documentation Project. A nonprofit organisation which maintains GNU/Linux documentation. It's mostly known for documents such as HOWTOs, but it also maintains FAQs, and even a few books.

Ver Também FAQ.

traverse

For a directory on a UNIX® system, this means that the user is allowed to go through this directory, and possibly to directories under it. This requires that the user has execute permission on this directory.

URL

Uniform Resource Locator. A string with a special format used to identify a resource on the Internet in a unique way. The resource may be a file, a server or other item. The syntax for a URL is

protocol://user:password@server.name[:port]/path/to/resource.

When only a machine name is given and the protocol is http://, it defaults to retrieving the file that the server is configured to show by default, usually it the index.html file.

username

Is a name (or more generally a word) which identifies a user on a system. Each username is attached to a unique and single UID (user ID)

Ver Também login.

UTF-8

Unicode Transformation Format 8. It is an octet (8-bit) lossless encoding of Unicode characters. UTF-8 encodes each Unicode character as a variable number of 1 to 4 octets, where the number of octets depends on the integer value assigned to the Unicode character. It is an efficient encoding of Unicode documents that use mostly US-ASCII characters because it represents each character in the range U+0000 through U+007F as a single octet. UTF-8 is the default encoding for XML.

Ver Também ISO 8859, ASCII.

variables

Are strings which are used in Makefile files to be replaced by their value each time they appear. Usually they are set at the beginning of the Makefile. They are used to simplify Makefile and source files tree management.

More generally, variables in programming are words that refer to other entities (numbers, strings, tables, etc.) that are likely to vary while the program is executing.

verbose

For commands, the verbose mode means that the command reports to standard (or possibly error) output all the actions it performs and the results of those actions. Sometimes, commands have a way to define the “verbosity level”, which means that the amount of information that the command will report can be controlled.

VESA

Video Electronics Standards Association. An industry standards association aimed at the PC architecture. For example, it is the author of the SVGA standard.

virtual console

Is the name given to what used to be called terminals. On GNU/Linux systems, you have what are called virtual consoles which enable you to use one screen or monitor for many independently running sessions. By default, you have six virtual consoles which can be reached by pressing ALT-F1 through ALT-F6. There is a seventh virtual console, ALT-F7, which will permit you to reach a running X Window System. In X, you can reach the text console by pressing CTRL-ALT-F1 through CTRL-ALT-F6.

Ver Também console.

virtual desktops

In the X Window System, the window manager may provide you with several desktops. This handy feature allows you to organise your windows, avoiding the problem of having dozens of them stacked on top of each other. It works as if you had several screens. You can switch from one virtual desktop to another in a manner which depends on the window manager you're using.

Ver Também window manager, desktop.

WAN

Wide Area Network. This network, although similar to a LAN, connects computers on networks which are not physically connected to the same wiring and are separated by a greater distance.

Ver Também LAN.

wildcard

The '*' and '?' characters are used as wildcard characters and may represent anything. The '*' represents any number of characters, including no characters. The '?' represents exactly one character. Wildcards are often used in regular expressions.

window

In networking, the window is the largest amount of data that the receiving end can accept at a given point in time.

In the context of a graphical user environment, a window is the rectangle that occupies a given running application which usually contains a title, a menu, a status bar, and the application's work area.

window manager

The program responsible for the “look and feel” of a graphical environment, dealing with window bars, frames, buttons, root menus, and some keyboard shortcuts. Without it, it would be hard or impossible to have virtual desktops, to resize windows on the fly, to move them around, ...

workspace switcher

A little applet which allows you to switch between the available virtual desktops. It is also known as pager.

Ver Também virtual desktops.