Domain Name Server (BIND)

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 the need to remember IP addresses. 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.

Ok lets move towards INSTALLATION procedure...

At a terminal prompt, enter the following command to install dns:

sudo apt-get install bind9

A very useful package for testing and troubleshooting DNS issues is the dnsutils package. To install dnsutils enter the following:

sudo apt-get install dnsutils

Now its time to configure your own DNS...

The default configuration is setup to act as a caching server. All that is required is simply adding the IP Addresses of your ISP's DNS servers. Simply uncomment and edit the following in /etc/bind/named.conf.options:

forwarders {
                  4.2.2.2;
                  5.6.7.8;
};

	(Replace 4.2.2.2 and 5.6.7.8 with the IP Adresses of actual nameservers.)

Now restart the DNS server, to enable the new configuration. From a terminal prompt:

sudo /etc/init.d/bind9 restart
 
  

For the newbies.. there are 3 types of DNS servers : Cache server, Primary Master & Secondary Master.

Primary Master

In this section BIND9 will be configured as the Primary Master for the domain example.com. Simply replace example.com with your FQDN (Fully Qualified Domain Name).

Forward Zone File

To add a DNS zone to BIND9, turning BIND9 into a Primary Master server, the first step is to edit /etc/bind/named.conf.local:

zone "example.com" {
 type master;
        file "/etc/bind/db.example.com";
};

Now use an existing zone file as a template to create the /etc/bind/db.example.com file:

sudo cp /etc/bind/db.local /etc/bind/db.example.com

Edit the new zone file /etc/bind/db.example.com change localhost. to the FQDN of your server, leaving the additional "." at the end. Change 127.0.0.1 to the nameserver's IP Address and root.localhost to a valid email address, but with a "." instead of the usual "@" symbol, again leaving the "." at the end.
Also, create an A record for ns.example.com. The name server in this example:

;
; BIND data file for local loopback interface
;
$TTL    604800
@       IN      SOA     ns.example.com. root.example.com. (
                              2         ; Serial
                         604800         ; Refresh
                          86400         ; Retry
                        2419200         ; Expire
                         604800 )       ; Negative Cache TTL
;
@       IN      NS      ns.example.com.
@       IN      A       127.0.0.1
@       IN      AAAA    ::1
ns      IN      A       192.168.1.10

You must increment the Serial Number every time you make changes to the zone file. If you make multiple changes before restarting BIND9, simply increment the Serial once.

Once you have made a change to the zone file BIND9 will need to be restarted for the changes to take effect:

sudo /etc/init.d/bind9 restart

Reverse Zone File

Now that the zone is setup and resolving names to IP Adresses a Reverse zone is also required. A Reverse zone allows DNS to resolve an address to a name.
Edit /etc/bind/named.conf.local and add the following:

zone "1.168.192.in-addr.arpa" {
        type master;
        notify no;
        file "/etc/bind/db.192";
};

(Replace 1.168.192 with the first three octets of whatever network you are using. Also, name the zone file /etc/bind/db.192 appropriately.)


Now create the /etc/bind/db.192 file:

sudo cp /etc/bind/db.127 /etc/bind/db.192

Next edit /etc/bind/db.192 changing the basically the same options as /etc/bind/db.example.com:

;
; BIND reverse data file for local loopback interface
;
$TTL    604800
@       IN      SOA     ns.example.com. root.example.com. (
                              2         ; Serial
                         604800         ; Refresh
                          86400         ; Retry
                        2419200         ; Expire
                         604800 )       ; Negative Cache TTL
;
@       IN      NS      ns.
10      IN      PTR     ns.example.com.

The Serial Number in the Reverse zone needs to be incremented on each changes as well. For each A record you configure in /etc/bind/db.example.com you need to create a PTR record in /etc/bind/db.192.

After creating the reverse zone file restart BIND9:

sudo /etc/init.d/bind9 restart

Secondary Master

Once a Primary Master has been configured a Secondary Master is needed in order to maintain the availability of the domain should the Primary become unavailable.
First, on the Primary Master server, the zone transfer needs to be allowed. Add the allow-transfer option to the example Forward and Reverse zone definitions in /etc/bind/named.conf.local:

zone "example.com" {
                                 type master;
                                 file "/etc/bind/db.example.com";
                                 allow-transfer {
                                                         192.168.1.11;
                                 };
};

zone "1.168.192.in-addr.arpa" {
                                type master;
                                notify no;
                                file "/etc/bind/db.192";
                                allow-transfer {
                                                         192.168.1.11;
                                };
};

(Replace 192.168.1.11 with the IP Address of your Secondary nameserver.)


Next, on the Secondary Master, install the bind9 package the same way as on the Primary. Then edit the /etc/bind/named.conf.local and add the following declarations for the Forward and Reverse zones:

zone "example.com" {
                                  type slave;
                                  file "/var/cache/bind/db.example.com";
                                  masters {
                                                 192.168.1.10;
                                  };
};

zone "1.168.192.in-addr.arpa" {
                                  type slave;
                                  file "/var/cache/bind/db.192";
                                  masters {
                                                 192.168.1.10;
                                  };
};

(Replace 192.168.1.10 with the IP Address of your Primary nameserver.)


Restart BIND9 on the Secondary Master:

sudo /etc/init.d/bind9 restart



OPTIONAL :

Logging

BIND9 has a wide variety of logging configuration options available. There are two main options. The channel option configures where logs go, and the category option determines what information to log.
If no logging option is configured the default option is:

logging {
     category default { 

default_syslog; 

default_debug; 

};
     category unmatched { 

null; 

};
};

This section covers configuring BIND9 to send debug messages related to DNS queries to a separate file.

• First, we need to configure a channel to specify which file to send the messages to. Edit /etc/bind/named.conf.local and add the following:
  
  

  logging {
      channel query.log {      
          file "/var/log/query.log";
          severity debug 3; 
      }; 
  };

• Next, configure a category to send all DNS queries to the query file:
  
  

  logging {
      channel query.log {      
          file "/var/log/query.log"; 
          severity debug 3; 
      }; 
      category queries { query.log; }; 
  };

• Since the named daemon runs as the bind user the /var/log/query.log file must be created and the ownership changed:
  
  
  

  sudo touch /var/log/query.log
  sudo chown bind /var/log/query.log

• Before named daemon can write to the new log file the AppArmor profile must be updated. First, edit /etc/apparmor.d/usr.sbin.named and add:
  
  

  /var/log/query.log w,

  
  Next, reload the profile:
  
  

  cat /etc/apparmor.d/usr.sbin.named | sudo apparmor_parser -r

  
  
• Now restart BIND9 for the changes to take effect:
  
  

  sudo /etc/init.d/bind9 restart

You should see the file /var/log/query.log fill with query information. This is a simple example of the BIND9 logging options.