Linux03_DNS

Jainul
1

13-FEB-2014

Thursday

Linux-Linux-Linux-Linux-Linux-Linux-Linux-Linux-Linux-Linux-Linux-LinuxLinux-Linux-Linux-Linux

Topic:

Domain
Name
Server

(Introduction, Installation, Configure DNS)

Jainul
2

Domain Name Server [DNS]

The Domain Name System (DNS) is a
hierarchical distributed naming system
for computers, services, or any resource
connected to the Internet or a private
network.

The Internet, and many larger private
Internet Protocol (IP) networks, rely on
the Domain Name System (DNS) to help
direct traffic.

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The DNS maintains a distributed
database of network names and
addresses.

It provides methods for computers to
remotely query the database.
Some people call DNS the "phone book
of the Internet."

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Domain Name Service (DNS) is an
Internet service that maps IP
addresses and fully qualified domain
names (FQDN) to one another
In this way, DNS alleviates/relieves
the need to remember IP addresses.

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DNS Servers and Name Hierarchy

• DNS uses client/server network
architecture.
• DNS servers are the computers
designated to store DNS database
records (names and addresses),
while clients of the DNS include
PCs, phones and other devices of
end users.

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DNS Servers and Name Hierarchy

• DNS servers also interface with
each other, acting as clients to each
other when needed.
• The DNS organizes its servers into
a hierarchy.

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• For the Internet, so-called root name
servers reside at the top of the DNS
hierarchy
• The Internet root name servers manage
DNS server information for the Web's
top-level domains (TLD) (like ".com"
and ".uk"), specifically the names and IP
addresses of the original (called
authoritative) DNS servers responsible
for answering queries about each TLD
individually.

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• Servers at the next lower level of the DNS
hierarchy track second-level domain names
and addresses (like "about.com"), and
additional levels manage Web domains (like
"compnetworking.about.com").

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The domain name is a component of a
Uniform/universal Resource Locator (URL)
used to access web sites…
for example:

URL: http://www.w3schools.net/index.html
Top-level domain name: net
Second-level domain name: w3schools.net
Host name: www.w3schools.net

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• Computers that run DNS are
called name servers.

• Ubuntu ships with BIND (Berkley
Internet Naming Daemon), the most
common program used for maintaining
a name server on Linux.

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Installation

• At a terminal prompt, enter the following
command to install dns:
$ sudo apt-get install bind9

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Implementation of BIND

• BIND is an acronym for the Berkeley
Internet Name Domain project, which is a
group that maintains the DNS-related
software suite that runs under Linux.
• The most well known program in BIND is
named, the daemon that responds to DNS
queries from remote machines.

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• A DNS server does not know all the IP
addresses in the world, but networks with
other DNS servers which it can query to
find an unknown address.
• Most UNIX systems can run named, which
is part of the bind (Berkeley Internet
Name Domain) package distributed by the
Internet Software Consortium.

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• It can run as a stand-alone caching
nameserver, which is often done on Linux
systems in order to speed up network
access.
• Your main client configuration file is
/etc/resolv.conf , which determines the
order in which Domain Name Servers are
contacted:

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• search somewhere.org
• nameserver 192.168.42.1
• nameserver 193.74.208.137
bind9 name server installation for DNS
-On Ubuntu Linux server
apt-get install bind9 dnsutils
-Fedora alternative:
yum install bind dnsutils

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18

•

In computer networking, reverse DNS lookup

or reverse DNS resolution (rDNS) is the
determination of a domain name that is
associated with a given IP address using the
Domain Name Service (DNS) of the Internet.
• Computer networks use the Domain Name
System to determine the IP address associated
with a domain name. This process is also known
as forward DNS resolution. Reverse DNS
lookup is the inverse process, the resolution of
an IP address to its designated domain name.

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• A DNS server, or name server, is used to
resolve an IP address to a hostname or
vice versa.

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You can set up four different types of DNS servers:
1. A master DNS server for your domain(s),

Which stores authoritative records for your domain.

2. A slave DNS server,
Which relies on a master DNS server for data.

3. A caching-only DNS server,
Which stores recent requests like a proxy server. It
otherwise refers to other DNS servers.

4. A forwarding-only DNS server,
Which refers all requests to other DNS servers.

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The entire hostname with its domain such as
server.example.com is called a fully
qualified domain name (FQDN).

The right-most part of the FQDN such as .com
or .net is called the top level domain, with the
remaining parts of the FQDN, which are
separated by periods, being sub-domains.

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• These sub-domains are used to divide
FQDN(Fully Qualified Domain Name)s into
zones, with the DNS information for each
zone being maintained by at least one
authoritative name server.
• The authoritative server that contains the
master zone file, which can be modified to
update DNS information about the zone, is
called the primary master server, or just
master server.

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• The additional name servers for the zone
are called secondary servers or slave
servers.
• Secondary servers retrieve information
about the zone through a zone transfer
from the master server or from another
secondary server.
• DNS information about a zone is never
modified directly on the secondary
server.

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• NEXT ….
• Configuring DNS…

Linux03_DNS

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