Monday, May 5, 2008

Some Important Definitions

http connection : http connection means the requests server receives for accessing your website. In other words http connection indicates the traffic to your website.

iptables : it is a packet filtering tool which allows system administrator to define incoming and outgoing packets to a system using certain rules.

Virtual Private Server(VPS): is a virtual private server, which is functionally identical to an isolated standalone server, with its own IP addresses, processes, files, its own users database, its own configuration files, its own applications, system libraries, and so on. Virtual Private Servers share one Hardware Node and one OS kernel. However, they are isolated from each other.Virtual Private Server 0 is used to designate the Hardware Node itself.

Virtuozzo : which allows you to create multiple isolated Virtual Private Servers on a single physical server to share hardware, licenses, and management effort with maximum efficiency.

SSH : SSH stands for Secure Shell. It is a protocol for logging on to a remote machine and executing commands on that machine. It provides secure encrypted communications between two untrusted hosts over an insecure network.

Domainkeys: DomainKeys is an email authentication technology developed by Yahoo, and is primarily used as an additional anti-spam and anti-phishing method and to prove and protect email sender identity.

fsck : The system utility fsck (for "file system check" or "file system consistency check") is a tool for checking the consistency of a file system in the Unix system.

Generally, fsck is run automatically at boot time when the system detects that a file system is in an inconsistent state, indicating a non-graceful shutdown, such as a crash or power loss. Typically, fsck utilities provide options for either interactively repairing damaged file systems (the user must decide how to fix specific problems), automatically deciding how to fix specific problems (so the user doesn't have to answer any questions), or reviewing the problems that need to be resolved on a file system without actually fixing them.

Fsck can also be run manually by the system administrator if there is believed to be a problem with the file system.

IP : The Internet Protocol (IP) is a protocol used for communicating data across a packet-switched internetwork. IP is a network layer protocol in the Internet protocol suite and is encapsulated in a data link layer protocol (e.g., Ethernet). In short, the way in which packets of data are addressed and sent across the Internet.

Firewall : A firewall is a program configured to permit, deny, or encrypt incoming and outgoing traffic in a system based on a set of rules and other criteria.

runlevel : The term runlevel refers to a mode of operation in one of the computer. Conventionally, seven runlevels exist, numbered from zero to six, though up to ten, from zero to nine, may be used. When a computer enters runlevel zero, it halts, and when it enters runlevel six, it reboots.
Additional runlevels are as follows :

1 Single-User Mode
2 Multi-User Mode
3 Multi-User Mode with Networking
4 Unused
5 X11

spf record : SPF helps mail servers distinguish forgeries from real mail by making it possible for a domain owner to say, "I only send mail from these machines." That way, if any other machines try to send mail from that domain, the mail server knows that the FROM address is forged.

Due to the fact that a significant majority of SPAM comes from forged addresses, a new Sender Policy Framework (SPF) standard is being implemented by a number of ISPs and mail hosts, including several major providers (Hotmail, Yahoo, AOL, etc). Those providers have begun to require SPF to allow mail through their networks. Mail systems will need SPF records for their domains if they want their mail to be accepted by those providers.

Protocol - An agreed upon format for transmitting data between two devices. In short a 'rule'.

IP address - The format of an IP address is a 32-bit(4 byte) numeric address written as four numbers separated by periods. Each number can be zero to 255. For example, could be an IP address. It is analogous to your telephone number in that the telephone number is used by the telephone network to direct calls to you. The IP address is used by the Internet to direct data to your computer, e.g. the data your web browser retrieves and displays when you surf the net.

Web server - A computer that delivers or "serves up" web pages which are then viewed in web browsers. Requires an Internet connection, server software, an IP address, and a domain name.

Subnet—A portion of a network sharing a particular subnet address.

Subnet mask - A 32-bit combination used to describe which portion of an address refers to the subnet and which part refers to the host.

Interface - A network connection.

Daemon : a daemon (pronounced /ˈdiːmən/ or /ˈdeɪmən/[1]) is a computer program that runs in the background, rather than under the direct control of a user; they are usually initiated as background processes. Typically daemons have names that end with the letter "d": for example, syslogd, the daemon that handles the system log, or sshd, which handles incoming SSH connections.

Transmission Control Protocl (TCP) : is the protocol that creates connections between two computer over the internet, allowing them to pass data back and forth. TCP is made to allow the transmitted data to be reassembled into the proper form when it reached its destination.

chkrootkit (Check Rootkit) : is a common Unix-based program intended to help system administrators check their system for known rootkits.

A rootkit is a program (or combination of several programs) designed to take fundamental control (in Unix terms "root" access, in Windows "Administrator" access) of a computer system, without authorization by the system's owners and legitimate managers. Access to the hardware (e.g., the reset switch) is rarely required as a rootkit is intended to seize control of the operating system running on the hardware.

Load Average : It is the average sum of the number of processes waiting in the run-queue plus the number currently executing over 1, 5, and 15 minute time periods.


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