mirror of https://github.com/tLDP/LDP
956 lines
45 KiB
XML
956 lines
45 KiB
XML
<glossary id="Glossary">
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<title>Glossary</title>
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ARPA
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The Advanced Research and Projects Agency of the United States Department of Defense.
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Also known as DARPA (the "D" stands for "Defense"), it originated in the late 1960s
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and early 1970s the proposal and standards for the Internet. For this reason, the
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Internet was initially referred to as ARPANet, and connected the military with the
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various centers of research around the United States in a way that was intended to
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have a high degree of survivability against a nuclear attack.
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BASH
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The Bourne Again Shell and is based on the Bourne shell, sh, the original command interpreter.
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Bourne Shell
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The Bourne shell is the original Unix shell (command execution program, often called a
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command interpreter) that was developed at AT&T. Named for its developer, Stephen
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Bourne, the Bourne shell is also known by its program name, sh. The shell prompt (character
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displayed to indicate readiness for input) used is the $ symbol. The Bourne shell family
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includes the Bourne, Korn shell, bash, and zsh shells. Bourne Again Shell (bash) is the
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free version of the Bourne shell distributed with Linux systems. Bash is similar to the
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original, but has added features such as command line editing. Its name is sometimes
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spelled as Bourne Again SHell, the capitalized Hell referring to the difficulty some people
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have with it.
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CLI
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A CLI (command line interface) is a user interface to a computer's operating system or an
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application in which the user responds to a visual prompt by typing in a command on a
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specified line, receives a response back from the system, and then enters another command,
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and so forth. The MS-DOS Prompt application in a Windows operating system is an example of
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the provision of a command line interface. Today, most users prefer the graphical user interface
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(GUI) offered by Windows, Mac OS, BeOS, and others. Typically, most of today's Unix-based systems
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offer both a command line interface and a graphical user interface.
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core
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A core file is created when a program terminates unexpectedly, due to a bug, or a violation of
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the operating system's or hardware's protection mechanisms. The operating system kills the
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program and creates a core file that programmers can use to figure out what went wrong. It
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contains a detailed description of the state that the program was in when it died. If would
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like to determine what program a core file came from, use the file command, like this: $ file core
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That will tell you the name of the program that produced the core dump. You may want to write
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the maintainer(s) of the program, telling them that their program dumped core. To Enable or
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Disable Core Dumps you must use the ulimit command in bash, the limit command in tcsh, or the
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rlimit command in ksh. See the appropriate manual page for details. This setting affects all
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programs run from the shell (directly or indirectly), not the whole system. If you wish to enable
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or disable core dumping for all processes by default, you can change the default setting in
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/usr/include/linux/sched.h. Refer to definition of INIT_TASK, and look also in
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/usr/include/linux/resource.h. PAM support optimizes the system's environment, including the amount
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of memory a user is allowed. In some distributions this parameter is configurable in the
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/etc/security/limits.conf file. For more information, refer to the Linux Administrator's Security Guide.
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daemon
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A process lurking in the background, usually unnoticed, until something triggers it into action.
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For example, the \cmd{update} daemon wakes up every thirty seconds or so to flush the buffer cache,
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and the \cmd{sendmail} daemon awakes whenever someone sends mail.
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DARPA
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The Defense Advanced Research Projects Agency is the central research and development organization
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for the Department of Defense (DoD). It manages and directs selected basic and applied research
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and development projects for DoD, and pursues research and technology where risk and payoff are
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both very high and where success may provide dramatic advances for traditional military roles and
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missions.
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DHCP
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Dynamic Host Control Protocol, is a protocol like BOOTP (actually dhcpd includes much of the
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functionality of BOOTPD). It assigns IP addresses to clients based on lease times. DHCP is used
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extensively by Microsoft and more recently also by Apple. It is probably essential in any
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multi-platform environment.
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DNS
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Domain Name System translates Internet domain and host names to IP addresses. DNS implements a
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distributed database to store name and address information for all public hosts on the Net.
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DNS assumes IP addresses do not change (i.e., are statically assigned rather than dynamically
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assigned). The DNS database resides on a hierarchy of special-purpose servers. When visiting a
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Web site or other device on the Net, a piece of software called the DNS resolver (usually built
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into the network operating system) first contacts a DNS server to determine the server's IP
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address. If the DNS server does not contain the needed mapping, it will in turn forward the
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request to a DNS server at the next higher level in the hierarchy. After potentially several
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forwarding and delegation messages are sent within the DNS hierarchy, the IP address for the
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given host eventually is delivered to the resolver. DNS also includes support for caching requests
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and for redundancy. Most network operating systems allow one to enter the IP addresses of
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primary, secondary, and tertiary DNS servers, each of which can service initial requests from
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clients. Many ISPs maintain their own DNS servers and use DHCP to automatically assign the
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addresses of these servers to dial-in clients, so most home users need not be aware of the
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details behind DNS configuration. Registered domain names and addresses must be renewed
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periodically, and should a dispute occur between two parties over ownership of a given name,
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such as in trademarking, ICANN's Uniform Domain-Name Dispute-Resolution Policy can be invoked.
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Also known as Domain Name System, Domain Name Service, Domain Name Server.
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environment variable
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A variable that is available to any program that is started by the shell.
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ESD
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Enlightened Sound Daemon. This program is designed to mix together several digitized audio streams
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for playback by a single device.
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filesystem
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The methods and data structures that an operating system uses to keep track of files on a
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disk or partition; the way the files are organized on the disk. Also used to describe a
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partition or disk that is used to store the files or the type of the filesystem.
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FSSTND
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Often the group, which creates the Linux File System Structure document, or the document itself,
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is referred to as the 'FSSTND'. This is short for "file system standard". This document has
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helped to standardize the layout of file systems on Linux systems everywhere. Since the original
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release of the standard, most distributors have adopted it in whole or in part, much to the benefit
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of all Linux users.
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GUI
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Graphical User Interface. The use of pictures rather than just words to represent the input and
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output of a program. A program with a GUI runs under some windowing system (e.g. The X Window
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System, Microsoft Windows, Acorn RISC OS, NEXTSTEP). The program displays certain icons, buttons,
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dialogue boxes etc. in its windows on the screen and the user controls it mainly by moving a pointer
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on the screen (typically controlled by a mouse) and selecting certain objects by pressing buttons
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on the mouse while the pointer is pointing at them. Though Apple Computer would like to claim they
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invented the GUI with their Macintosh operating system, the concept originated in the early 1970s
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at Xerox's PARC laboratory.
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hard link
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A directory entry, which maps a filename to an inode, number. A file may have multiple names or
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hard links. The link count gives the number of names by which a file is accessible. Hard links
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do not allow multiple names for directories and do not allow multiple names in different filesystems.
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init
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'init' process is the first user level process started by the kernel. init has many important
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duties, such as starting getty (so that users can log in), implementing run levels, and taking
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care of orphaned processes. This chapter explains how init is configured and how you can make
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use of the different run levels. init is one of those programs that are absolutely essential to
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the operation of a Linux system, but that you still can mostly ignore. Usually, you only need
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to worry about init if you hook up serial terminals, dial-in (not dial-out) modems, or if you
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want to change the default run level. When the kernel has started (has been loaded into memory,
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has started running, and has initialized all device drivers and data structures and such), it
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finishes its own part of the boot process by starting a user level program, init. Thus, init
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is always the first process (its process number is always 1). The kernel looks for init in a
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few locations that have been historically used for it, but the proper location for it is
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/sbin/init. If the kernel can't find init, it tries to run /bin/sh, and if that also fails,
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the startup of the system fails. When init starts, it completes the boot process by doing a
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number of administrative tasks, such as checking filesystems, cleaning up /tmp, starting various
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services, and starting a getty for each terminal and virtual console where users should be able
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to log in. After the system is properly up, init restarts getty for each terminal after a user
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has logged out (so that the next user can log in). init also adopts orphan processes: when a
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process starts a child process and dies before its child, the child immediately becomes a child
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of init. This is important for various technical reasons, but it is good to know it, since it
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makes it easier to understand process lists and process tree graphs. init itself is not allowed
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to die. You can't kill init even with SIGKILL. There are a few variants of init available. Most
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Linux distributions use sysvinit (written by Miquel van Smoorenburg), which is based on the
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System V init design. The BSD versions of Unix have a different init. The primary difference is
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run levels: System V has them, BSD doesn't.
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inode
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An inode is the address of a disk block. When you see the inode information through ls, ls
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prints the address of the first block in the file. You can use this information to tell if
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two files are really the same file with different names (links). A file has several
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components: a name, contents, and administrative information such as permissions and
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modification times. The administrative information is stored in the inode (over the years,
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the hyphen fell out of "i-node"), along with essential system data such as how long it is,
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where on the disc the contents of the file are stored, and so on. There are three times in
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the inode: the time that the contents of the file were last modified (written); the time
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that the file was last used (read or executed); and the time that the inode itself was last
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changed, for example to set the permissions. Altering the contents of the file does not
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affect its usage time and changing the permissions affects only the inode change time. It
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is important to understand inodes, not only to appreciate the options on ls, but because in
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a strong sense the inodes are the files. All the directory hierarchy does is provide
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convenient names for files. The system's internal name for the file is its i-number: the
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number of the inode holding the file's information.
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kernel
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Part of an operating system that implements the interaction with hardware and the sharing
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of resources.
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libraries
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Executables should have no undefined symbols, only useful symbols; all useful programs refer
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to symbols they do not define (eg. printf or write). These references are resolved by pulling
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object files from libraries into the executable.
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link
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A symbolic link (alias in MacOS and shortcut under Windows) is a file that points to another
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file; this is a commonly used tool. A hard-link rarely created by the user, is a filename
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that points to a block of data that has several other filenames as well.
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man page
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Every version of UNIX comes with an extensive collection of online help pages called man
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pages (short for manual pages). The man pages are the authoritative documentation about
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your UNIX system. They contain complete information about both the kernel and all the utilities.
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MTA
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Mail Transfer Agents. Alongside the web, mail is the top reason for the popularity of the
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Internet. E-mail is an inexpensive and fast method of time-shifted messaging which, much
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like the Web, is actually based around sending and receiving plain text files. The
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protocol used is called the Simple Mail Transfer Protocol (SMTP). The server programs
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that implement SMTP to move mail from one server to another are called MTAs. Once upon
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a time users would have to Telnet into an SMTP server and use a command line mail program
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like 'mutt' or 'pine' to check their mail. Now, GUI based e-mail clients like Mozilla,
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Kmail and Outlook allow users to check their email off of a local SMTP sever. Additional
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protocols like POP3 and IMAP4 are used between the SMTP server and desktop mail client to
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allow clients to manipulate files on, and download from, their local mail server. The
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programs that implement POP3 and IMAP4 are called Mail Delivery Agents (MDAs). They are
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generally separate from MTAs.
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NFS
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Network File System, is the UNIX equivalent of Server Message Block (SMB). It is a way
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through which different machines can import and export local files between each other.
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Like SMB though, NFS sends information including user passwords unencrypted, so it's best
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to limit its usage to within your local network.
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operating system
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Software that shares a computer system's resources (processor, memory, disk space, network
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bandwidth, and so on) between users and the application programs they run. Controls access
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to the system to provide security.
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PAM
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Pluggable Authentication Modules. A suite of shared libraries that determine how a user
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will be authenticated. For example, conventionally UNIX users authenticate themselves by
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supplying a password at the password prompt after they have typed their name at the login
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prompt. In many circumstances, such as internal access to workstations, this simple form
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of authentication is considered sufficient. In other cases, more information is warranted.
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If a user wants to log in to an internal system from an external source, like the Internet,
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more or alternative information may be required - perhaps a one-time password. PAM
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provides this type of capability and much more. Most important, PAM modules allow you to
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configure your environment with the necessary level of security.
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PATH
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The shell looks for commands and programs in a list of file paths stored in the PATH
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environment variable. An environment variable stores information in a place where other
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programs and commands can access it. Environment variables store information such as the
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shell that you are using, your login name, and your current working directory. To see a
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list of all the environment variables currently defined; type 'set' at the prompt. When
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you type a command at the shell prompt, the shell will look for that command's program
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file in each directory listed in the PATH variable, in order. The first program found
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matching the command you typed will be run. If the command's program file is not in a
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directory listed in you PATH environment variable, the shell returns a "commands not found"
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error. By default, the shell does not look in your current working directory or your home
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directory for commands This is really a security mechanism so that you don't execute
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programs by accident. What if a malicious user put a harmful program called ls in your
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home directory? If you typed ls and the shell looked for the fake program in your home
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directory before the real program in the /bin directory, what do you think would happen?
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If you thought bad things, you are on the right track. Since your PATH doesn't have the
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current directory as one of its search locations, programs in your current directory
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must be called with an absolute path of a relative path specified as './program-name'.
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To see what directories are part of your PATH enter this command:
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# echo $PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/bin/X11
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pipes and sockets
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Special files that programs use to communicate with one another. They are rarely seen,
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but you might be able to see a socket or two in the /dev/ directory.
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process identifier
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Shown in the heading of the ps command as PID. The unique number assigned to every
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process running in the system.
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rpc
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Remote Procedure Calls. It enables a system to make calls to programs such as NFS
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across the network transparently, enabling each system to interpret the calls as
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if they were local. In this case, it would make exported filesystems appear as
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thought they were local.
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set group ID (SGID)
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The SGID permission causes a script to run with its group set to the group of the
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script, rather than the group of the user who started it. It is normally considered
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extremely bad practice to run a program in this way as it can pose many security
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problems. Later versions of the Linux kernel will even prohibit the running of shell
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scripts that have this attribute set.
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set user ID (SUID)
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The SUID permission causes a script to run as the user who is the owner of the script,
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rather than the user who started it. It is normally considered extremely bad practice
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to run a program in this way as it can pose many security problems. Later versions of
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the Linux kernel will even prohibit the running of shell scripts that have this attribute
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set.
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signal
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Software interrupts sent to a program to indicate that an important event has occurred.
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The events can vary from user requests to illegal memory access errors. Some signals,
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like the interrupt signal, indicate that a user has asked the program to do something
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that is not in the usual flow of control.
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SSH
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The Secure Shell, or SSH, provides a way of running command line and graphical
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applications, and transferring files, over an encrypted connection, all that will
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be seen is junk. It is both a protocol and a suite of small command line applications,
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which can be used for various functions. SSH replaces the old Telnet application,
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and can be used for secure remote administration of machines across the Internet.
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However, it also has other features. SSH increases the ease of running applications
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remotely by setting up X permissions automatically. If you can log into a machine,
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it allows you to run a graphical application on it, unlike Telnet, which requires
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users to have an understanding of the X authentication mechanisms that are manipulated
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through the xauth and xhost commands. SSH also has inbuilt compression, which allows
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your graphic applications to run much faster over the network. SCP (Secure Copy) and
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SFTP (Secure FTP) allow transfer of files over the remote link, either via SSH's own
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command line utilities or graphical tools like Gnome's GFTP. Like Telnet, SSH is
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cross-platform. You can find SSH server and clients for Linux, Unix and all flavours
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of Windows, BeOS, PalmOS, Java and embedded Oses used in routers.
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STDERR
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Standard error. A special type of output used for error messages. The file
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descriptor for STDERR is 2.
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STDIN
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Standard input. User input is read from STDIN. The file descriptor for STDIN is 0.
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STDOUT
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Standard output. The output of scripts is usually to STDOUT. The file descriptor
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for STDOUT is 1.
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symbol table
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The part of an object table that gives the value of each symbol (usually
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as a section name and an offset) is called the symbol table. Executables may
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also have a symbol table, with this one giving the final values of the symbols.
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Debuggers use the symbol table to present addresses to the user in a symbolic,
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rather than a numeric form. It is possible to strip the symbol table from
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executables resulting in a smaller sized executable but this prevents
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meaningful debugging.
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symbolic link or soft link
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A special filetype, which is a small pointer file, allowing multiple names
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for the same file. Unlike hard links, symbolic links can be made for directories
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and can be made across filesystems. Commands that access the file being pointed
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to are said to follow the symbolic link. Commands that access the link itself do
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not follow the symbolic link.
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system call
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The services provided by the kernel to application programs, and the way in
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which they are invoked. See section 2 of the manual pages.
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system program
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Programs that implement high level functionality of an operating system,
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i.e., things that aren't directly dependent on the hardware. May sometimes
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require special privileges to run (e.g., for delivering electronic mail), but
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often just commonly thought of as part of the system (e.g., a compiler).
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tcp-wrappers
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Almost all of the services provided through inetd are invoked through tcp-wrappers
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by way of the tcp-wrappers daemon, tcpd. The tcp-wrappers mechanism provides access
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control list restrictions and logging for all service requests to the service it
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wraps. It may be used for either TCP or TCP services as long as the services are
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invoked through a central daemon process such as inetd. These programs log the
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client host name of incoming telnet, ftp, rsh, rlogin, finger etc.... requests.
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Security options are access control per host, domain and/or service; detection of
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host name spoofing or host address spoofing; booby traps to implement an
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early-warning system.
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ZSH
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Zsh was developed by Paul Falstad as a replacement for both the Bourne and C shell.
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It incorporates features of all the other shells (such as file name completion and
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a history mechanism) as well as new capabilities. Zsh is considered similar to the
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Korn shell. Falstad intended to create in zsh a shell that would do whatever a
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programmer might reasonably hope it would do. Zsh is popular with advanced users.
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Along with the Korn shell and the C shell, the Bourne shell remains among the three
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most widely used and is included with all UNIX systems. The Bourne shell is often
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considered the best shell for developing scripts.
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Base<EFBFBD>10
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Well known decimal number system, represent any value with digit 0-9.
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Base<EFBFBD>16
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Usually used in lower and higher programming languages, known also as
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hexadecimal number system, represent any value with digit 0-9 and char
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A-F (case insensitive).
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Base<EFBFBD>85
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Representation of a value with 85 different digits/chars, this can lead
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to shorter strings but never seen in the wild.
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Bit
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Smallest storage unit, on/true (1) or off/false (0)
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Byte
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Mostly a collection of 8 (but not really a must - see older computer
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systems) bits
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Device
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Here, hardware of network connection, see also NIC
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Dual<EFBFBD>homed<EFBFBD>host
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A dual homed host is a node with two network (physical or virtual)
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interfaces on two different links, but does not forward any packets
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between the interfaces.
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Host
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Generally a single homed host on a link. Normally it has only one active
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network interface, e.g. Ethernet or (not and) PPP.
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Interface
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Mostly same as "device", see also NIC
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IP<EFBFBD>Header
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Header of an IP packet (each network packet has a header, kind of is
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depending on network layer)
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Link
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A link is a layer 2 network packet transport medium, examples are
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Ethernet, Token Ring, PPP, SLIP, ATM, ISDN, Frame Relay,...
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Node
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A node is a host or a router.
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Octet
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A collection of 8 real bits, today also similar to "byte".
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Port
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Information for the TCP/UDP dispatcher (layer 4) to transport information
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to upper layers
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Protocol
|
||
Each network layer contains mostly a protocol field to make life easier
|
||
on dispatching transported information to upper layer, seen in layer 2
|
||
(MAC) and 3 (IP)
|
||
|
||
Router
|
||
A router is a node with two or more network (physical or virtual)
|
||
interfaces, capable of forwarding packets between the interfaces.
|
||
|
||
Socket
|
||
An IP socket is defined by source and destination IP addresses and Ports
|
||
and (binding)
|
||
|
||
Stack
|
||
Network related a collection of layers
|
||
|
||
Subnetmask
|
||
IP networks uses bit masks to separate local networks from remote ones
|
||
|
||
Tunnel
|
||
A tunnel is typically a point-to-point connection over which packets are
|
||
exchanged which carry the data of another protocol, e.g. an IPv6-in-IPv4
|
||
tunnel.
|
||
|
||
ACL
|
||
Access Control List
|
||
|
||
API
|
||
Application Programming Interface
|
||
|
||
ASIC
|
||
Application Specified Integrated Circuit
|
||
|
||
BSD
|
||
Berkeley Software Distribution
|
||
|
||
CAN-Bus
|
||
Controller Area Network Bus (physical bus system)
|
||
|
||
ISP
|
||
Internet Service Provider
|
||
|
||
KAME
|
||
Project - a joint effort of six companies in Japan to provide a free IPv6
|
||
and IPsec (for both IPv4 and IPv6) stack for BSD variants to the world
|
||
[http://www.kame.net/] www.kame.net
|
||
|
||
LIR
|
||
Local Internet Registry
|
||
|
||
NIC
|
||
Network Interface Card
|
||
|
||
RFC
|
||
Request For Comments - set of technical and organizational notes about
|
||
the Internet
|
||
|
||
USAGI
|
||
UniverSAl playGround for Ipv6 Project - works to deliver the production
|
||
quality IPv6 protocol stack for the Linux system.
|
||
|
||
CGI Script
|
||
A Common Gateway Interface Script. This is a program which is
|
||
run on demand to generate the content of a web page. If a web
|
||
page has to do more than simply feed an unchanging text and
|
||
graphics display to the viewer, you will probably need some sort
|
||
of dynamic content generation program such as a CGI Script.
|
||
Examples include discussion boards, feedback forms, e-commerce
|
||
shopping carts, and more.
|
||
|
||
DHCP
|
||
Dynamic Host Configuration Protocol. A standard, defined in RFC
|
||
1531, for computers on a TCP/IP network to request from a
|
||
central server information such as the IP number they should be
|
||
using, the netmask, the gateway, etc. Rather than an
|
||
administrator entering this information into the machine
|
||
configuration, the machine simply requests it from the server as
|
||
it is preparing to attach to the network.
|
||
|
||
DNS
|
||
Domain Name Service. A standard for translating domain names
|
||
into ``IP Number''s, or vice versa, by looking up data in
|
||
centralized databases.
|
||
|
||
DSL
|
||
Digital Subscriber Line. A relatively high speed network
|
||
connection, usually delivered through specialized telephone
|
||
wiring.
|
||
|
||
Dynamic IP Number
|
||
An ``IP Number'' which is assigned periodically or on a per-
|
||
session basis. No guarantee is made that the number will remain
|
||
constant. A dynamic IP number might change only when your
|
||
network connection hangs up and reconnects, or it might change
|
||
periodically under ``DHCP'' negotiation. Certain session-based
|
||
services such as telnet and ssh will stop working if the IP
|
||
number of either end of the connection is changed during the
|
||
session.
|
||
|
||
Forward DNS Query
|
||
A ``DNS'' query which converts a domain name into an ``IP
|
||
Number''.
|
||
|
||
FTP
|
||
The File Transfer Protocol. A standard system for sending files
|
||
between machines over the Internet.
|
||
|
||
ftpd
|
||
The daemon responsible for providing ``FTP'' services on a host.
|
||
It responds to queries initiated by a remote client.
|
||
|
||
Internet Service Provider
|
||
See ``ISP''.
|
||
|
||
IP
|
||
See ``IP Number''.
|
||
|
||
IP Number
|
||
The ``address'' of a certain network interface. Under the
|
||
current addressing standard, called ipv4, this number consists
|
||
of four 8-bit values, generally written as base-10 numbers
|
||
separated by dots. Communication between computers on the
|
||
Internet is based on packets of information sent between IP
|
||
numbers.
|
||
|
||
ISP
|
||
Internet Service Provider. The company which provides your
|
||
network connectivity, including connection hardware, service
|
||
hosting, and leasing out the IP numbers under their control.
|
||
|
||
Masquerading
|
||
A form of filtering in which packets from one machine to the
|
||
outside world have their headers rewritten so that they appear
|
||
to come from an intermediate machine. That intermediate machine
|
||
then passes responses back to the originating machine. The net
|
||
effect is that an entire network of machines can appear to use a
|
||
single IP number, that of the masquerading host, for the purpose
|
||
of outgoing connections.
|
||
|
||
named
|
||
The name server daemon. This is the daemon which answers ``DNS''
|
||
queries, and is distributed as part of the BIND package.
|
||
|
||
Network Time Protocol
|
||
See ``NTP''.
|
||
|
||
NTP
|
||
Network Time Protocol. A standard for synchronizing your system
|
||
clock with the ``true time'', defined as the average of many
|
||
high-accuracy clocks around the world.
|
||
|
||
OS Operating System.
|
||
Linux, Windows, FreeBSD, BeOS, HP-UX, etc.
|
||
|
||
PHB
|
||
Pointy-Haired Boss
|
||
<http://www.unitedmedia.com/comics/dilbert/about/html/boss.html>.
|
||
A creation of Scott Adams, of Dilbert fame.
|
||
|
||
Provider
|
||
See ``ISP''.
|
||
|
||
Reverse DNS Query
|
||
A ``DNS'' query which converts a ``IP Number'' into a domain
|
||
name.
|
||
|
||
Router
|
||
A specialized hardware device which implements rules for where
|
||
to send packets based on their ``IP Number''s, and which bridges
|
||
between your Ethernet hardware and whatever communications
|
||
medium connects you to your ``ISP''.
|
||
|
||
ssh
|
||
The secure shell. A cryptographically strong replacement for
|
||
rlogin, telnet, ftp, and other programs. Protects against
|
||
``spoofing'', man in the middle attacks, and packet sniffing.
|
||
|
||
Static IP Number
|
||
An ``IP Number'' which has been assigned or leased to you
|
||
permanently. Barring revocation of the agreement which granted
|
||
you this number, that IP number will always be available for
|
||
your use, and no other machine on the Internet is allowed to use
|
||
that number. Contrast this with ``Dynamic IP Number''s.
|
||
|
||
PSTN
|
||
Public Switched Telephone Network
|
||
|
||
VoIP
|
||
Voice over Internet Protocol
|
||
|
||
LAN
|
||
Local Area Network
|
||
|
||
WAN
|
||
Wide Area Network
|
||
|
||
TOS
|
||
Type Of Service
|
||
|
||
ISP
|
||
Internet Service Provider
|
||
|
||
RTP
|
||
Real Time Protocol
|
||
|
||
RSVP
|
||
ReSerVation Protocol
|
||
|
||
QoS
|
||
Quality of Service
|
||
|
||
client
|
||
The machine or program that initiates an action or a connection
|
||
for the purpose of gaining use of some service or data.
|
||
|
||
server
|
||
The machine or program that accepts incoming connections from
|
||
multiple remote machines and provides a service or data to
|
||
those.
|
||
|
||
Bindery
|
||
The bindery is a specialised database storing network
|
||
configuration information on a Novell fileserver. Netware
|
||
clients may query the bindery to obtain information on available
|
||
services, routing and user information.
|
||
|
||
Frame Type
|
||
is a term used to describe that actual protocol used to carry
|
||
the IPX (and IP) datagrams across your ethernet style network
|
||
segments. There are four common ones. They are:
|
||
|
||
Ethernet_II
|
||
This is a refined version of the original DIX ethernet
|
||
standard. Novell has been allocated a formal protocol id and
|
||
this means that both IPX and IP can coexist happily in an
|
||
Ethernet_II environment quite happily. This is commonly used
|
||
in Novell environments and is a good choice.
|
||
|
||
802.3
|
||
This is an I.E.E.E. protocol defining a Carrier Sense
|
||
Multiple Access with Collision Detection (CSMA/CD) mechanism.
|
||
It was based on the original DIX Ethernet standard, with an
|
||
important modification, the type (protocol id) field was
|
||
converted into a length field instead. It is for this reason
|
||
that IPX really shouldn't be run here. IEEE 802.3 was
|
||
designed to carry IEEE 802.2 frames only but there are
|
||
implementations that use it to carry IPX frames directly and
|
||
remarkably it does work. Avoid it unless you are trying to
|
||
interwork with a network already configured to use it.
|
||
|
||
802.2
|
||
This is an I.E.E.E. protocol that defines a set of Logical
|
||
Link Control procedures. It provides a simplistic way of
|
||
allowing different protocols to coexist, but is quite limited
|
||
in this respect. Novell uses an unofficial Service Address
|
||
Point (like a protocol id) but since everyone else uses it as
|
||
well, that hasn't yet presented too much of a problem.
|
||
|
||
SNAP
|
||
SNAP is the Sub Network Access Protocol. This protocol is
|
||
designed ride on top of 802.3 and 802.2. It expands the
|
||
multiprotocol capability of 802.2 and provides some measure
|
||
of compatability with existing Ethernet and Ethernet_II frame
|
||
types.
|
||
|
||
IPX
|
||
Internet Packet eXchange is a protocol used by the Novell
|
||
corporation to provide internetworking support for their
|
||
NetWare(tm) product. IPX is similar in functionality to the IP
|
||
protocol used by the tcp/ip community.
|
||
|
||
IPX network address
|
||
This is a number which uniquely identifies a particular IPX
|
||
network. The usual notation for this address is in hexadecimal.
|
||
An example might look like: 0x23a91002.
|
||
|
||
IPX Internal network
|
||
This is a virtual IPX network. It is virtual because it does not
|
||
correspond to a physical network. This is used to provide a
|
||
means of uniquely identifying and addressing a particular IPX
|
||
host. This is generally only useful to IPX hosts that exist on
|
||
more than one physical IPX network such as fileservers. The
|
||
address is coded in the same form as for a physical IPX network.
|
||
|
||
RIP
|
||
Routing Information Protocol is a protocol used to automatically
|
||
propagate network routes in an IPX network. It is functionally
|
||
similar to the RIP used within the tcp/ip community.
|
||
|
||
NCP
|
||
NetWare Core Protocol is a networked filesystem protocol
|
||
designed by the Novell Corporation for their NetWare(tm)
|
||
product. NCP is functionally similar to the NFS used in the
|
||
tcp/ip community.
|
||
|
||
SAP
|
||
Service Advertisement Protocol is a protocol designed by the
|
||
Novell Corporation that is used to advertise network services in
|
||
a NetWare(tm) environment.
|
||
|
||
Hardware address
|
||
This is a number that uniquely identifies a host in a physical
|
||
network at the media access layer. Examples of this are Ethernet
|
||
Addresses. An Ethernet address is generally coded as six
|
||
hexadecimal values separated by colon characters eg.
|
||
00:60:8C:C3:3C:0F
|
||
|
||
route
|
||
The route is the path that your packets take through the network
|
||
to reach their destination.
|
||
|
||
ARP
|
||
This is an acronym for the Address Resolution Protocol and this
|
||
is how a network machine associates an IP Address with a
|
||
hardware address.
|
||
|
||
ATM
|
||
This is an acronym for Asynchronous Transfer Mode. An ATM
|
||
network packages data into standard size blocks which it can
|
||
convey efficiently from point to point. ATM is a circuit
|
||
switched packet network technology.
|
||
|
||
client
|
||
This is usually the piece of software at the end of a system
|
||
where the user is. There are exceptions to this, for example, in
|
||
the X11 window system it is actually the server with the user
|
||
and the client runs on the remote machine. The client is the
|
||
program or end of a system that is receiving the service
|
||
provided by the server. In the case of peer to peer systems such
|
||
as slip or ppp the client is taken to be the end that initiates
|
||
the connection and the remote end, being called, is taken to be
|
||
the server.
|
||
|
||
datagram
|
||
A datagram is a discrete package of data and headers which
|
||
contain addresses, which is the basic unit of transmission
|
||
across an IP network. You might also hear this called a
|
||
`packet'.
|
||
|
||
DLCI
|
||
The DLCI is the Data Link Connection Identifier and is used to
|
||
identify a unique virtual point to point connection via a Frame
|
||
Relay network. The DLCI's are normally assigned by the Frame
|
||
Relay network provider.
|
||
|
||
Frame Relay
|
||
Frame Relay is a network technology ideally suited to carrying
|
||
traffic that is of bursty or sporadic nature. Network costs are
|
||
reduced by having many Frame Relay customer sharing the same
|
||
network capacity and relying on them wanting to make use of the
|
||
network at slightly different times.
|
||
|
||
Hardware address
|
||
This is a number that uniquely identifies a host in a physical
|
||
network at the media access layer. Examples of this are Ethernet
|
||
Addresses and AX.25 Addresses.
|
||
|
||
ISDN
|
||
This is an acronym for Integrated Services Digital Network. ISDN
|
||
provides a standardized means by which Telecommunications
|
||
companies may deliver either voice or data information to a
|
||
customers premises. Technically ISDN is a circuit switched data
|
||
network.
|
||
|
||
|
||
ISP
|
||
This is an acronym of Internet Service Provider. These are
|
||
organizations or companies that provide people with network
|
||
connectivity to the Internet.
|
||
|
||
|
||
IP address
|
||
This is a number that uniquely identifies a TCP/IP host on the
|
||
network. The address is 4 bytes long and is usually represented
|
||
in what is called the "dotted decimal notation", where each byte
|
||
is represented in decimal from with dots `.' between them.
|
||
|
||
|
||
MSS
|
||
The Maximum Segment Size (MSS) is the largest quantity of data
|
||
that can be transmitted at one time. If you want to prevent
|
||
local fragmentation MSS would equal MTU-IP header.
|
||
|
||
|
||
MTU
|
||
The Maximum Transmission Unit (MTU) is a parameter that
|
||
determines the largest datagram than 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 unfragmented. 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 SLIP interface.
|
||
|
||
route
|
||
The route is the path that your datagrams take through the
|
||
network to reach their destination.
|
||
|
||
server
|
||
This is usually the piece of software or end of a system remote
|
||
from the user. The server provides some service to one or many
|
||
clients. Examples of servers include ftp, Networked File
|
||
System, or Domain Name Server. 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.
|
||
|
||
|
||
window
|
||
The window is the largest amount of data that the receiving end
|
||
can accept at a given point in time.
|
||
|
||
Linux
|
||
supplies the operating system. It is a stable Unix
|
||
implementation providing true multi-user multi-tasking services
|
||
with full network (TCP/IP e. a.) support. Except from the
|
||
actual media and transmission cost, it is available free of
|
||
charge and comes in form of so-called distributions which
|
||
usually include everything needed from the basic OS to text
|
||
processing, scripting, software development, interface builders,
|
||
etc.
|
||
|
||
HTML
|
||
is the Hypertext Markup Language used to build interfaces to
|
||
network systems like Intranets and the WWW, the World Wide Web.
|
||
HTML is very simple and can be produced with any ASCII-capable
|
||
text editor.
|
||
|
||
Browsers
|
||
are text-based (e. g. Lynx) or graphical (e. g. Mosaic,
|
||
Netscape, Arena etc.) applications accepting, evaluating and
|
||
displaying HTML documents. They are the only piece of software
|
||
which is directly operated by the database user. Using browsers,
|
||
it is possible to display various types of data (text, possibly
|
||
images) and communicate with http servers (see next) on about
|
||
every popular computer model for which a browser has been made
|
||
available.
|
||
|
||
http servers
|
||
provide access to the area of a host computer where data
|
||
intended for public use in a network are stored. They understand
|
||
the http protocol and procure the information the user requests.
|
||
|
||
SQL
|
||
Structured Query Language is a language for manipulating data in
|
||
relational databases. It has a very simple grammar and is a
|
||
standard with wide industry support. SQL-based databases have
|
||
become the core of the classical client/server database concept.
|
||
There are many famous SQL systems available, like Oracle,
|
||
Informix etc., and then there is also msql which comes with a
|
||
very low or even zero price tag if it is used in academical and
|
||
educational environments.
|
||
|
||
CGI
|
||
Common Gateway Interface is the programming interface between
|
||
the system holding the data (in our case an SQL-based system)
|
||
and the network protocol (HTML, of course). CGIs can be built
|
||
around many programming languages, but a particularly popular
|
||
language is perl.
|
||
|
||
perl
|
||
is an extremely powerful scripting language which combines all
|
||
merits of C, various shell languages, and stream manipulation
|
||
languages like awk and sed. Perl has a lot of modularized
|
||
interfaces and can be used to control SQL databases, for
|
||
example.
|
||
|
||
DBM
|
||
DataBase Management, a library of functions which maintain key-content
|
||
pairs in a data base.
|
||
|
||
DLL
|
||
Dynamically Linked Library, a library linked to an executable program at
|
||
run-time.
|
||
|
||
domainname
|
||
A name "key" that is used by NIS clients to be able to locate a suitable
|
||
NIS server that serves that domainname key. Please note that this does
|
||
not necessarily have anything at all to do with the DNS "domain" (machine
|
||
name) of the machine(s).
|
||
|
||
FTP
|
||
File Transfer Protocol, a protocol used to transfer files between two
|
||
computers.
|
||
|
||
libnsl
|
||
Name services library, a library of name service calls (getpwnam,
|
||
getservbyname, etc...) on SVR4 Unixes. GNU libc uses this for the NIS
|
||
(YP) and NIS+ functions.
|
||
|
||
libsocket
|
||
Socket services library, a library for the socket service calls (socket,
|
||
bind, listen, etc...) on SVR4 Unixes.
|
||
|
||
NIS
|
||
Network Information Service, a service that provides information, that
|
||
has to be known throughout the network, to all machines on the network.
|
||
There is support for NIS in Linux's standard libc library, which in the
|
||
following text is referred to as "traditional NIS".
|
||
|
||
NIS+
|
||
Network Information Service (Plus :-), essentially NIS on steroids. NIS+
|
||
is designed by Sun Microsystems Inc. as a replacement for NIS with better
|
||
security and better handling of _large_ installations.
|
||
|
||
NYS
|
||
This is the name of a project and stands for NIS+, YP and Switch and is
|
||
managed by Peter Eriksson <peter@ifm.liu.se>. It contains among other
|
||
things a complete reimplementation of the NIS (= YP) code that uses the
|
||
Name Services Switch functionality of the NYS library.
|
||
|
||
NSS
|
||
Name Service Switch. The /etc/nsswitch.conf file determines the order of
|
||
lookups performed when a certain piece of information is requested.
|
||
|
||
RPC
|
||
Remote Procedure Call. RPC routines allow C programs to make procedure
|
||
calls on other machines across the network. When people talk about RPC
|
||
they most often mean the Sun RPC variant.
|
||
|
||
YP
|
||
Yellow Pages(tm), a registered trademark in the UK of British Telecom
|
||
plc.
|
||
|
||
TCP-IP
|
||
Transmission Control Protocol/Internet Protocol. It is the data
|
||
communication protocol most often used on Unix machines.
|
||
|
||
PSTN (Public Service Telephone Network)
|
||
is the telephone system that is used thoughout the U.S. and many other
|
||
countries. Although never intended for networking, telephone lines can
|
||
be used for communications for computers.
|
||
|
||
A modem (modulator/demodulator) is used to interface between a computer and
|
||
the telephone system. Modems can convert data into audible tones and back.
|
||
The fastest two-way modems currently available support a speed of 33.6 Kbps
|
||
(kilobits per second).
|
||
|
||
Current modems advertise speeds up to 56 Kbps per second. These modems rely
|
||
on digital equipment being used in the phone company's central office and in
|
||
the facility (such as the Internet Service Provider) you are dialling into.
|
||
The 56 Kbps speed also works in only one direction; the other direction supports
|
||
33.6 Kbps.
|
||
|
||
protocol
|
||
A protocol is a set of rules governing the format and meaning of the frames,
|
||
packets, or messages within a layer and can be changed at will by entities,
|
||
provided that they do not change the service visible to their users.
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||
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||
</glossary>
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