/var/named/

The /var/named/ directory is typically used to store zone files and other DNS-related data for the BIND (Berkeley Internet Name Domain) DNS server. This directory contains the actual data files that BIND uses to serve DNS information to clients. Understanding the structure and purpose of the files in this directory is essential for managing a BIND DNS server.

Structure and Contents of /var/named/

1. Zone Files

   • These files contain DNS records for the zones managed by the DNS server.

2. Configuration Files

   • These may include additional configuration settings or include files referenced by the primary configuration file (named.conf).

3. Dynamic Update Files

   • Files that are updated dynamically by the DNS server as DNS records change, often used with Dynamic DNS (DDNS).

4. Journal Files

   • These files contain changes to zone files that are made via dynamic updates.

Common Files in /var/named/

1. Zone Files

   • Example: db.example.com

   • This file contains the DNS records for the example.com domain.

   $TTL 86400
   @   IN  SOA ns1.example.com. admin.example.com. (
               2024010101 ; Serial
               3600       ; Refresh
               1800       ; Retry
               1209600    ; Expire
               86400 )    ; Minimum TTL
   ;
   @       IN  NS    ns1.example.com.
   @       IN  NS    ns2.example.com.
   ns1     IN  A     192.168.1.1
   ns2     IN  A     192.168.1.2
   www     IN  A     192.168.1.3

2. Reverse Zone Files

   • Example: db.192.168.1

   • This file contains the reverse DNS records for the 192.168.1.0/24 subnet.

   $TTL 86400
   @   IN  SOA ns1.example.com. admin.example.com. (
               2024010101 ; Serial
               3600       ; Refresh
               1800       ; Retry
               1209600    ; Expire
               86400 )    ; Minimum TTL
   ;
   @       IN  NS    ns1.example.com.
   @       IN  NS    ns2.example.com.
   1       IN  PTR   ns1.example.com.
   2       IN  PTR   ns2.example.com.
   3       IN  PTR   www.example.com.

3. Dynamic Update Files

   • Example: db.example.com.jnl

   • This journal file is used for recording changes made via DDNS.

4. Root Hint File

   • Example: db.root

   • This file contains a list of root DNS servers used by BIND to resolve queries for which it is not authoritative.

   ; This file is named db.root
   ; 
   .       3600000 IN NS    A.ROOT-SERVERS.NET.
   A.ROOT-SERVERS.NET. 3600000 A 198.41.0.4
   ; (Additional root servers here)

Configuring BIND to Use Files in /var/named/

In the named.conf configuration file, the paths to the zone files are specified relative to the /var/named/ directory.

Example Configuration in named.conf

zone "example.com" {
    type master;
    file "/var/named/db.example.com";
    allow-update { none; };
};

zone "1.168.192.in-addr.arpa" {
    type master;
    file "/var/named/db.192.168.1";
    allow-update { none; };
};

Managing Files in /var/named/

1. Creating Zone Files

   • Manually create and edit zone files using a text editor.

2. Securing the Directory

   • Ensure that the directory and files have the appropriate permissions to prevent unauthorized access.

   chown -R named:named /var/named
   chmod -R 750 /var/named

3. Dynamic Updates

   • Allow dynamic updates if using DDNS. Ensure proper ACLs are set in the named.conf to restrict updates to trusted sources.

   zone "example.com" {
       type master;
       file "/var/named/db.example.com";
       allow-update { key ddns_key; };
   };
   
   key ddns_key {
       algorithm hmac-md5;
       secret "base64-encoded-secret";
   };

4. Managing Journal Files

   • BIND will automatically manage journal files for dynamic zones. These files should not be manually edited.

5. Root Zone File Updates

   • Update the root hints file (db.root) periodically to ensure it contains current root server information.

Conclusion

The /var/named/ directory is a critical component of the BIND DNS server, housing the zone files and other essential data. Proper configuration and management of this directory are vital for ensuring reliable and secure DNS operations. Understanding its contents and how to manage them effectively will help maintain a robust DNS infrastructure.