Glossary

Some TLAs and definitions to help you get started. (What's a "TLA"? Look it up below.) The terms are not in alphabetical order; they are roughly in order of their importance to a typical cluster user.

Abbreviations

TLA

NFS

Network Filesystem. This is a method for one machine to share ("export") a disk with another machine on the network. The file /etc/exports contains the list of disk partitions that a Linux system will allow others to see.

NIS

Network Information Services. This is a means of keeping databases synchronized between different machines on a network. Typically, NIS is used to synchronize the account and network files (e.g., /etc/passwd, /etc/group, /etc/netgroup, /etc/hosts).

AMD

Automount daemon. This is a program that automatically mounts a disk onto your systems if you access a specific directory on your machine. For example, if you type =cd /a/home/tanya=, AMD can automatically mount the /home directory from the computer tanya.

DNS

Domain Name Services. This is a program that translates an IP name (e.g., tanya.nevis.columbia.edu) into an IP address (e.g., 192.12.82.81). A computer that is a DNS server typically maintains a database of corresponding IP names and addresses, and is aware of similar databases maintained at remote sites.

SSH

Secure Shell. A means of communicating between two computers using an encrypted connection.

POP

Post Office Protocol. A simple method of reading your mail. Your messages are stored on whatever computer is running your mail reader program.

IMAP

Internet Message Access Protocol (this is a four-letter acronym). A more advanced protocol for reading mail. Your messages can be stored in any location you choose; typically this is on whatever computer is your mail server.

DHCP

Dynamic Host Configuration Protocol (another FLA). This service allows a device to dynamically receive an IP address from a pool of addresses, instead of requiring the device to have a fixed IP address. This is ideal for devices like laptops, which will not all be connected to the network at all times.

Definitions

Server

A computer or a program that provides some common functionality for others to use. A "master" or "primary" server is the main source for a given service. A "slave" or "secondary" server is the backup source for a given service; if the master server goes down, the slave takes up its task.

Client

A computer or program that makes use of a server's functionality.

Applications Server

A machine with commonly-used programs or libraries; in particle physics, these would be programs such as CERNLIB, GEANT, and ROOT. The purpose of an applications server is to simplify administration of those programs: only one copy of a program exists that's used by several computers, instead of a copy for each computer.

Batch Server (or Workgroup Server)

A fast machine intended for executing big jobs such as Monte Carlos. A batch server offers its CPU cycles for running applications. Typically, users run utility programs such as X-windows on their client machines without slowing down the applications on the batch server.

NIS Server

A machine that is the central source for the files synchronized by NIS.

Mail Server

A machine configured to handle mail for several users. The purpose of a mail server is to simplify administration; since mail can be complex to configure, it's easier to manage mail services on one machine than it is to have each user's machine handle mail. It's also better to isolate mail services for security reasons.

File Server

Basically, a machine with a lot of disk storage attached to it. The purpose of a file server is to make that disk space (and the files within) available to other machines.

Backup Server

A machine responsible for making backups of the disks on the cluster.

Print Server

A machine that acts as a central print queue for a given printer or printers. This helps prevent a printer from "clogging" its internal print queue by receiving many printer requests from many computers.

Web server (or WWW server or HTTP server)

A machine that delivers web pages to browsers (e.g., Firefox or Explorer) running on remote computers.