Setting DNS server

dns server in Linux

A DNS server, or name server, is used to resolve an IP address to a hostname or vice versa.
You can set up four different types of DNS servers:

·         A master DNS server for your domain(s), which stores authoritative records for your domain.

·         A slave DNS server, which relies on a master DNS server for data.

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

·         A forwarding-only DNS server, which refers all requests to other DNS servers.

Before configuring BIND to create a DNS server, you must understand some basic DNS concepts.

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.

These sub-domains are used to divide FQDNs into zones, with the DNS information for each zone being maintained by at least oneauthoritative 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.

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

chroot features

chroot feature is run named as user named, and it also limit the files named can see. When installed, named is fooled into thinking that the directory /var/named/chroot is actually the root or / directory. Therefore, named files normally found in the /etc directory are found in /var/named/chroot/etc directory instead, and those you would expect to find in /var/named are actually located in/var/named/chroot/var/named.

The advantage of the chroot feature is that if a hacker enters your system via a BIND exploit, the hacker's access to the rest of your system is isolated to the files under the chroot directory and nothing else. This type of security is also known as a chroot jail.

Configure dns server

In this example we will configure a dns server and will test from client side.

For this example we are using three systems one linux server one linux clients and one window clients.

bind and caching-nameserver rpm is required to configure dns. check them for install if not found install them.
 
set hostname to server.example.com and ip address to 192.168.0.254

main configuration file for dns server is named.conf. By default this file is not created in /var/named/chroot/etc/ directory. Instead of named.conf a sample file /var/named/chroot/etc/named.caching-nameserver.conf is created. This file is use to make a caching only name server. You can also do editing in this file after changing its name
to named.conf to configure master dns server or you can manually create a new named.conf file.