Configure Key Linux Components - Glossary

Action

Actions make up the second part of an /etc/syslog.conf rule. They are associated with selectors and perform tasks such as log the message to a file, broadcast the message to all logged-in users, write the message to the system console, or transmit the message to remote logging daemons across the network.

ATAPI/IDE

ATAPI (AT Attachment Packet Interface) is a standard for connecting CD-ROM and tape backup drives to your computer via a standard hardware interface, and is part of the Enhanced IDE. Generally, IDE (Integrated Drive Electronics) is used as an interface to address hard disk drives

Automount point

An automount point is a user-specified filesystem under which the automounter mounts a particular filesystem.

Automounter

An automounter is a program that automatically mounts filesystems when those filesystems are first accessed.

Automounting

Automounting allows the system to automatically mount filesystems when those filesystems are first accessed.

Backdoor

A hole placed in you r security by a cracker. It allows the intruder to gain easy access to your system by bypassing normal security.

BIOS

Basic Input and Output System. The BIOS is responsible for providing a standard interface to the computer hardware. An operating system writes to a particular BIOS specification, rather than worrying about the details for all supported hardware.

Block size

Block size is the number of bytes allocated to individually accessible units in the ext2 filesystem.

Boot loader

The boot loader is program that is responsible for loading the rest of the operating system into the computer's memory at boot time.

Bridging

Bridges isolate segments of the same network to cut down on overall network traffic.

Compiler

A program that converts source code into an executable machine binary.

Configuration file

A configuration file contains information such as settings or options to be used by a hardware device or program.

Console

The console is the terminal display.

Core dump

A core dump copies the contents of random access memory (RAM) to the hard disk.

Cracker

An individual who breaks into systems or breaks copy protection of software products.

CVS

CVS, Concurrent Versions System, is a system that keeps a set of files in sync.

Daemon

A daemon is a program that waits for a request from another program. The daemon then performs the desired action, such as creating an http session, or opening and maintaining a communications socket. Some common daemons include httpd, telnetd, and ftpd.

Demand loading

Loading functionality only when it is needed.

Developmental

Developmental modules are still being tested and improved. If you chose to use one, be aware that it may include many unresolved bugs.

Device drivers

A unit of code written to interact with a specific hardware device.

Dump core

The action a process takes when it encounters a fatal error. A core file (also known as a core dump) is usually created to aid in debugging.

Extra-version specification

The extra-version specification is used to distinguish between various configurations of the same kernel version. It is separated from the traditional version by a hyphen.

Facility

Facilities are simply programs that can be configured to send notices to the system log. Common facilities include user, kern, mail, daemon, auth, lpr, news, uucp, and cron.

Firewalling

Firewalling protects one network from another. A computer acting as a firewall filters, logs, and audits traffic flowing from one network into the other.

Instance

A particular session of any object, where each session has particular characteristics that identify it uniquely. For example, a red car is an instance of the general "car" object, and you can identify the car by its red characteristic.

IP

Internet Protocol. Usually combined with TCP (Transmission Control Protocol) in order to pass data between a destination and source.

IPX

Internetwork Packet Exchange protocol. IPX is a networking protocol.

IrDA

An acronym for Infrared Data Association, IrDA is an international standards body that plans the hardware and software requirements for wireless, infrared data communication.

ISDN

An acronym for Integrated Services Digital Network, ISDN is a standards specification for data transmission over telephone wires and other land-based media.

Kermit

A communications protocol developed at Columbia University.

Kernel

The core component of an operating system. The kernel is responsible for interfacing with the system hardware on user program's behalf, managing system memory and scheduling tasks to run.

Kernel ring buffer

The kernel ring buffer is an area of kernel memory with fixed size that holds the kernel's log message. As the kernel logs messages, older logs are overwritten.

Kernel thread

The Linux kernel is multi-threaded, meaning that multiple actions occur within the kernel simultaneously.

Logfiles

Logfiles are files that store information about the system's operation.

Major version

The major version is the first number included in the standard module naming convention. It specifies the kernel version.

Map file

In automounter parlance, the map file is a configuration file that associates a directory key with a device to mount when that directory key is accessed.

MD5 check

Uses a message digest algorithm to determine file integrity.

Memory footprint

The total amount of physical and swap memory a process uses.

Minor version

The minor version is the second number included in the standard module naming convention. It specifies the version of the kernel version. Odd numbers indicate developmental versions of a particular kernel and even numbers indicate a production or stable version of a particular kernel.

Mirroring

Mirroring uses n partitions that all store the same data for data redundancy and decreased read time.

Modem

A device that allows computers to send data over conventional analong phone lines.

Modular kernel

A modular kernel is one in which some drivers are built as object files, or modules, that the kernel can load on demand.

Modules

Modules are independent pieces of code that allow services such as additional hardware drivers to be loaded dynamically when needed by the kernel.

Monolithic kernel

A monolithic kernel is one in which support for all hardware, network protocols, and file systems is built within a single file.

Mount

A way of gaining access to a device that is not currently connected to your system.

Mount count

The number of mounts previously performed on a filesystem since the last filesystem check.

Network File System

NFS (Network File System) allows your system to share filesystems with other machines on the network.

Object files

Compiled source code (such as C or C++).

Packet sniffing

Packet sniffing is an example of spoofing in which a sniffing program is on a segment between two communicating end points. An intruder can then pretend to be one end of the connection to a victim and eavesdrop on data passed between the two end points.

Parallelization

Parallelization is the use of multiple hard drives for one purpose--to increase the speed and efficiency of the system.

Parity

Parity is the calculation of an additional stripe from the normal data stripes, to be used to recover lost data in the event of a drive failure.

Partition

A partition is a section of the hard drive reserved for specific directories, applications, or operating systems.

Patch level

The patch level is the third number included in the standard module naming convention. The greater the number, the more recent the patch is and the more likely bug fixes are implemented and security holes closed.

Permissions

File permissions specify which users and groups are allowed to read, write, or execute a particular file.

PPP

Point-to-Point Protocol. It is used to connect computers with the Internet.

Process

The computer's representation of a task. When a program is run from the command line, the binary is loaded into memory as a "process." The kernel shuffles processes around very quickly, simulating "simultaneous" program execution.

Process accounting

Maintains an account of every process ever executed.

Process auditing

Examines the process accounting logs and retrieves useful information.

Process ID

A process ID (PID) is a unique, non-negative number that you use to identify and control processes.

Protocol

Protocols identify the type of content communicated. One of the most common protocols is PPP, for communication to and from an Internet Service Provider.

QIC-80

QIC 80 is a tape standard that can be used to determine which tapes or devices will work with a particular operating system or backup utility.

raidtools

These are tools used to administer the RAID system. They are available in the raidtools-0.90-5.i386.rpm. Some of the commands include mkraid, raidstart, and raidstop.

Ramdisk

Ramdisks are block devices like hard disks and CD-ROM drives. However, ramdisks store their data in random access memory, as opposed to on disk. This is useful during installation.

Routing

The process of moving information from one network to another. It is very similar to bridging; however, routing works on the network layer.

RPM

An acronym for Red Hat Package Manager, an RPM is a group of files stored in a single portable file.

rsh

sh, the remote shell, is a utility that allows users to log in to a remote system. However, it does not use any type of encryption and therefore is insecure.

Rule

Every line in the /etc/syslog.conf file is called a rule. Rules map selectors to actions, which allows the Linux system logging facility to route messages of certain types to different locations.

Runaway process

A runaway process may consume vast quantities of memory, causing your machine to thrash, or the process may consume lots of CPU, slowing your machine down. Most problematically, the process may start wildly spawning children that will eventually bring your machine to an unusable state.

SCSI

Small Computer Systems Interface is a standard for connecting peripherals to your computer via a standard hardware interface.

Selector

Selectors make up the first part of an /etc/syslog.conf rule. A facility and severity combine to form a selector. mail.warn is an example of a typical selector.

Serial port

A serial port or interface that can be used for serial communication so that one bit of data is transmitted at a time.

Services

Services are simply programs, like sendmail or FTP that perform a task for the user.

Severity

The severity level indicates the importance of a given message. The severity levels listed from most importance to least important are: emerg, alert, crit, err, warning, notice, info, debug, and none.

Signal

A method of communicating between processes in UNIX.

SLIP

Serial Line Internet Protocol. SLIP is very similar to PPP.

Sniffer

A program that looks at all traffic on the network, trying to gain access to other systems.

Social engineering

The use of social techniques, such as masquerading as a system's administrator, in order to gain access to confidential user information like a password.

Spoofing

Using somebody else's IP address to create TCP/IP packets is called spoofing.

ssh

ssh, the secure shell, is a utility that allows log in to a remote system using encrypted data transfer.

Stable

A stable version is indicated by even minor version numbers and should not contain any crippling bugs.

Stanza

A block of commands in the /etc/lilo.conf file that define configuration values for a specific operating system.

Striping

Striping is the arrangement of contiguous disk blocks across multiple drives instead of within the same drive. Striping is intended to increase the efficiency of disk access by allowing concurrent seeks on multiple devices.

Swap space

Swap space is the space on a hard disk that computer uses as an extension of its RAM.

Swapping

Swapping uses space on a hard disk as an extension a computer's RAM. By utilizing swap, the operating system pretends that more RAM is available than the machine actually contains. The oldest files in RAM are "swapped out" to the swap partition until they are needed so that other data can be "swapped in" to RAM.

System accounting

Refers to the creation and maintenance of logs, which keep track of processes executed, user activity, and network connections.

System V

System V is an early version of UNIX that defined many characteristics of modern UNIX implementations.

Thrash

An activity which requires a great deal of paging, where a process spends more time paging than executing, causing a significant negative impact on a system's performance. Thrashing occurs when there isn't enough RAM to handle all the required processes -- the solution is to move a process to disk, thereby leaving enough space for other processes to complete.

Trust

Trust is a basic concept in security. The ability to trust means relying on the availability of another computer and the integrity of information provided by the other computer.

User auditing

Examines the system logs to determine information about user access.

Virtual consoles

Virtual consoles allow you to have simultaneous login sessions on the same machine without entering a GUI.

Xmodem

Xmodem is a popular file-transfer protocol.

Zmodem

Zmodem is similar, but has improved error detection