RedHat Linux System Administration - Glossary

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The development of Linux is one of the most prominent examples of free and open source software collaboration. Typically all the underlying source code can be used, freely modified, and redistributed by anyone under licenses such as the GNU General Public License. Linux is packaged in a format known as a Linux distribution for desktop and server use. Some popular mainstream Linux distributions include Debian (and its derivatives such as Ubuntu), Fedora, Redhat and openSUSE. Linux distributions include the Linux kernel and supporting utilities and libraries to fulfill the distribution's intended use.
The Address Resolution Protocol. ARP is the method Ethernet computers use to assign IP addresses to Ethernet card addresses.
Background process
A process that does not interact with the user through the terminal, and allows the shell to give the user a prompt immediately after issuing the command.
An older protocol used like DHCP to initialize hosts dynamically on a network. DHCP implements Bootp as a subset for backward compatibility with non-DHCP capable machines.
To send information to an IP address that all network hosts listen to. You can broadcast a message across an entire subnet.
A child process is a process that was spawned by another process. Commands you type in a shell produce children of the shell itself.
The particular graphics processing system used on a particular video card.
Config modes
The different methods computers use to obtain configuration information, either dynamic using DHCP/BOOTP or static.
A system that executes processes according to a schedule. Usually cron handles system maintenance routines, but any process can be scheduled with it.
A crontab is a file that contains the cron system scheduling table. Separate files hold the tables for each user and the system-wide cron services.
Dynamic Host Configuration Protocol. An open Standard for configuring hosts' interfaces at boot time.
Refers to modem connections to ISPs usually using the PPP protocol.
Display Manager
Software that allows users to log in via a graphical login window and be taken immediately into an X session.
The Domain Name Server protocol. It replaces the Host Table as the primary means of resolving hostnames into IP addresses on large networks.
A high speed network used for local networks among workstations and servers. Usually forms the basis of large academic and corporate networks.
Foreground process
A process that suspends the shell until it has finished executing.
A program that presents the login prompt and passes the user name to the authentication routines.
Each time you click a glossary term, you'll see a window like this one displaying the term and its definition. To see the entire glossary, click “Show All Terms.”
Host Table
A database of remote, network connected hosts maintained by each host on the network.
A communications system used to connect a Linux machine to a network.
A method used by computers to signal programs about outside events. For example, hardware you install has an IRQ setting that specifies which interrupt it uses when communicating with the processor.
IP address
A set of numbers that is a unique label for that interface on the network. It is represented by the notation X.X.X.X, where each X is a decimal number from 0 to 255.
The K Desktop Environment, like GNOME, is a network transparent desktop environment built on top of X. It usually uses the kwm window manager.
In databases, a key is a parameter that holds a value. For example the value of hostname could be its IP address.
Logical link
A type of file that is a reference to another real file.
To create a link from a directory name in the root hierarchy to a source of information. Sources of information include hard-disks, CD-ROMs, floppies, and drives on networked computers.

A set of numbers which indicates the network class. When its binary representation is anded with an interface IP address, the result is the network address.
Network File System
A protocol that uses remote procedure calls to mount remote drives to the local filesystem.
The Network Information Service. A protocol used to provide network information to clients upon request.
A tool that provides a centralized control point on an X display. It can hold applets for system monitors, program launch buttons and the GNOME pager.
A process is the parent of processes that it has spawned.
Sends the output of one command to the input of the next. This is accomplished on the command line by typing command1 | command2. The "|" symbol is called a pipe.
Point to Point Protocol. A Protocol used for a two machine network, usually used to connect a machine with a modem to a gateway.
Processes with more priority receive a greater share of system resources. Greater priority is signified by having a low priority number.
A process consists of a single program, a unique Process ID (PID), and a description of the process's environment.
Process environment
The set of environment variables associated with a particular process.
Process identification number (PID)
A unique number that is assigned to a process to distinguish it from all others on the system.
Process state
Describes whether the process is running, stopped, sleeping, uninterruptable sleep, or zombie.
To apply all transformations (scaling, skewing, rotating, etc.) to a font and display a string of characters on a graphical display.
Remote Procedure Call
A protocol through which applications receive information over a network without explicit knowledge of the network.
Subnets communicate through routers, so that only messages intended for a subnet's hosts are received. Without routing, data must be sent to every connected host, a very inefficient practice in large networks.
Specifies which system services are started up when Linux boots. Different runlevels start the services necessary for networking, multiple users, and graphical login sessions. The default runlevel for a Red Hat Linux graphical workstation is 5.
Runlevel editor
A program that automates symbolic link removal and creation when changing runlevel services.
Running process
A process that is executing the steps of its program. Linux switches the computer's resources between the running processes.
Scan rates
The rate at which horizontal scan lines are drawn on the monitor and the rate at which one entire sweep of the screen is made. These are referred to as the horizontal and vertical scan rates.
Linux can send signals to processes to control their actions, including termination, kill, and other signals.
Sleeping process
A process that has temporarily suspended operation because it is waiting for some event to wake it.
A process can start the execution of other processes. This is called spawning a process.
Stopped process
A process that the user has suspended or has stopped executing because it can not communicate with its terminal.
A set of machines that communicate without the assistance of a router. Networks and subnets are connected with routers to make larger networks.
A synonym for the root account. You are the superuser of a system when you log in as root.
Swap memory is space on a hard-drive that is used to hold excess data needed by processes. When a process becomes idle, it can be moved to the swap partition to free RAM for other processes.
Swapped process
A swapped process is a sleeping process that has been moved to swap memory to free up RAM.
Set of protocols that facilitate controlling the transmission of packets of information.
Part of a window border that is located at the top of the window and is used to drag the window and access window modification commands such as minimize and Shade. Shade "retracts" the window, leaving the title-bar in its place.
Uninterruptable sleeping process
A process that must wait for some event (usually some form of I/O) before proceeding in executing its program.
Window manager
Layer of the GUI system responsible for moving and resizing windows and handling other window events. It also provides configuration and organization.
X resource
Mechanism used to give user preference for window appearance to the X server.
X Window System
A collection of programs which act as an intermediate layer between X applications and the computer's video hardware, keyboard, and mouse.
A popular implementation of the X11R6 X Window System standard used by many operating systems. XFree86 is the default X server for Red Hat Linux.
Zombie process
A zombie process has only a PID, and no memory, program, or environment. It is created when a parent does not properly handle termination.
A number that has 32 binary digits. 32-bit IP addresses are written as four numbers separated by dots, X.X.X.X, where each number is in the range 0 to 255. Think of it as a string of 32 1's and 0's.
A standard filename used to specify X resources.
The main configuration file for XFree86, the X windows server used by Linux.
File in each user's home directory that controls graphical application and window manager startup when the X server is started.
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