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Linux Unix Network Administration - Glossary

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Address (A) record
An A record is a type of Resource Record that specifies an IP address-to-host name mapping.
Aliasing allows all users to refer to users by simple nicknames or by names other than their UNIX user name.
Authentication is the ability to verify the identity of a person or network host before engaging in a transaction.
authoritative server
A primary or secondary server for a zone is called an authoritative server when it obtains its information directly from data files describing the zone.
The automounter daemon provides a system for centralizing filesystem administration so the administrator can make any changes in the filesystem configuration from a central location.
BIND (Berkeley Internet Name Daemon) is the software that sets up a name server on a UNIX system.
caching-only name server
A caching-only name server is a name server process with no authoritative information of its own. Instead, it relies entirely on information obtained by recursion.
Canonical (CNAME) record
A CNAME record is a type of Resource Record that defines an alias.
Domain Name Service (DNS) is an Internet-wide service for converting numeric IP addresses to host names and back.
A domain is a distinct piece of the DNS namespace that is managed by a single administrative entity. A domain consists of a root domain, a top-level domain, a second-level domain, and a series of subdomains.
Encryption is the process of transforming a file using a mathematical function or technique so that the contents of the file are protected from unwanted viewing.
A firewall is a series of applications and hardware that filters and audits outside network traffic as it passes into your network.
Fully Qualified Domain Name (FQDN)
The Fully Qualifed Doman Name (FQDN) is the full path from the root of the DNS tree to that entity.
Group ID is a unique number that identifies a specific group.
To access all the items in the course glossary, click the Show All Terms button, below.
Host information (HINFO) record
An HINFO record is a type of Resource Record that gives the operating system and architecture for the specified host.
Kerberos is an authentication service that acts as a trusted third party to keep a centralized database of network users, much like NIS or NIS+. It vouches for hosts, allowing them to prove their identities.
M4 is a macro language that works with sendmail and, among other things, greatly simplifies sendmail configuration.
Mail Delivery Agent
A Mail Delivery Agent (MDA) copies the message from the Mail Transfer Agent (MTA) into the users mailbox file.
Mail Exchange (MX) record
An MX record is a type of Resource Record that defines a mail exchange host.
Mail Transfer Agent
A Mail Transfer Agent (MTA) is a program that routes email among different machines.
Mail User Agent
A Mail User Agent (MUA) is a program that allows users to compose, send, receive, and access email messages
Masquerading is the ability for a sendmail daemon to rewrite a subdomain's email address.
name server
A name server is a process that accepts queries into the DNS database. It is also fairly common usage to refer to the computer on which this process is running as a name server.
Name Server (NS) record
An NS record is a type of Resource Record that declares a machine to be a name server for a specified zone.
name server configuration file
The name server configuration file (/etc/named.boot) is a simple text file in which comment lines are indicated with a semicolon (;). Each line of the file addresses some aspect of name server configuration.
The DNS name server daemon
A netgroup is a way to refer to a specific group of hosts without having to list them individually. The netgroups are stored in an NIS map.
The Network File System (NFS) is a system for distributing filesystems across a network. Under this system, some machines, called NFS clients, can mount filesystems that are physically located on other machines, called NFS servers. An NFS server that makes file systems available for remote mounting is said to export or share those filesystems.
Network Information System (NIS) is a system for creating a distributed computing environment on a local network. NIS provides a network database of important configuration information and helps bind a network of machines into a single usable entity.
NIS map
NIS maps are a collection of database files that represent the data shared by the members of an NIS domain.
NIS+ is a substantially more powerful and substantially more secure version of NIS available on Solaris machines.
The nslookup program generates name server queries on command and is useful for debugging DNS.
packet sniffer
A packet sniffer is software that listens to traffic on a network and then either prints or records packets that meet user-specified criteria.
Pointer (PTR) record
A PTR record is a type of Resource Record that specifies a host name-to-IP address mapping.
primary server
Every zone must have exactly one associated primary name server. This name server is the unique location which has the official or authoritative information on its zone.
recursive queries
The distributed DNS database is bound together into a single unit by the process of recursive queries. Whenever a name server receives a query it cannot directly answer, then it generates a query of a name server higher in the DNS hierarchy.
Resource Records
Resource Records are the individual records in a zone file.
reverse lookup
Reverse lookup is a way to find a host's name by using that host's numeric IP address.The DNS system can convert IP addresses into names by associating a domain name with a network address.
root cache file
A root cache file is one of the name server data files and is used to prime the name server with the addresses of the root servers.
root server
The root servers are the servers for the root domain. They are operated by the InterNIC and play a crucial role in binding together the DNS database through the mechanism of recursion.
Remote Procedure Call (RPC)
secondary server
In addition to its primary server, a zone may have one or more secondary servers. A secondary server provides an alternative source for information on the zone.
Secure RPC
The Secure RPC protocol is an attempt to add a level of strong authentication to requests for NFS resources. It is based on a combined public-key/private-key encryption system.
The securenets file allows you to restrict access to your NIS server to hosts on particular networks or subnetworks.
The sendmail program is a daemon that transfers email between machines using the SMTP protocol or an older, essentially obsolete, protocol called UUCP (UNIX to UNIX Copy). It is the oldest and most commonly used Mail Transfer Agent for UNIX machines.
The server command instructs the nslookup program to use a different name server from the one listed in the /etc/resolv.conf file.
set type
The set type command asks the nslookup program to retrieve other kinds of Resource Records from the DNS database besides A and PTR records.
Simple Mail Transport Protocol (SMTP) is an application layer protocol for routing email.
State of Authority (SOA) record
An SOA record is a type of Resource Record that sets basic parameters for a DNS zone of authority and marks the beginning of a zone. Every zone or subzone must have exactly one SOA record and the zone continues until another SOA record is encountered.
A subdomain is any domain under the authority of another domain. For example, a top-level domain is a subdomain of the root domain, a second-level domain is a subdomain of a top-level domain, and so on.
Transmission Control Protocol (TCP) is a protocol that sends data from one program to another using Intenet Protocol (IP). TCP is connection-based and, therefore, more reliable than UDP.
User Datagram Protocol (UDP) is a procotol that sends data from one program to another using Internet Protocol (IP). UDP is less reliable than TCP because it provides unverified transportation for individual messages.
User ID is a unique number that identifies a specific user.
A zone is a branch of the DNS name space under the administrative control of some entity.
zone file transfer
Secondary servers obtain their data from the authoritative server by periodically downloading a copy of the authoritative server's zone files. This is called zone file transfer.
zone files
The data in the DNS database is stored in files, called zone files, which reside on the hosts running authoritative name servers for the zone.