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bind9

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🧭 BIND9: DNS Server Management

BIND9 is a widely-used, open-source DNS server software maintained by the Internet Systems Consortium (ISC). It supports advanced DNS features like DNSSEC, dynamic updates, and zone transfers, and is highly configurable.

🔍 Overview

Info

BIND9 is a robust and flexible DNS server that provides a variety of features like secure DNS (DNSSEC), dynamic updates, and zone transfers for managing DNS records effectively.

🛠️ Installation

Tip

Install BIND9 using the default package manager for quick setup on your system.

  • Ubuntu Linux: Install BIND9 via the default package manager:

    sudo apt install bind9

  • Ubuntu Docker: Canonical offers a hardened BIND9 image available via Docker:

    docker run -d --name bind9-container -e TZ=UTC -p 30053:53 ubuntu/bind9:9.18-22.04_beta

🧑‍💻 Configuration

🗂️ Named Configuration

Info

The main configuration file for BIND9 is named.conf, which defines global options and zones. It is typically found in /etc/bind, /etc/namedb, or /usr/local/etc/namedb.

Here’s an example for a simple domain configuration:

options {
    ...
};
 
zone "domain.tld" {
    type primary;
    file "domain.tld";
};

🗂️ Zone File

Tip

A zone file defines DNS records like A, MX, and NS records for a domain. Below is an example of a basic zone file configuration.

$TTL 2d
$ORIGIN domain.tld.
 
@         IN      SOA   ns1.domain.tld. hostmaster.domain.tld. (
                                      2022121200 ; serial number
                                      12h        ; refresh
                                      15m        ; retry
                                      3w         ; expiry
                                      2h         ; minimum TTL
                                  )
 
@         IN      NS      ns1.domain.tld.
3w        IN      MX  10  mail.domain.tld.
ns1       IN      A       192.168.254.2
mail      IN      A       192.168.254.4
joe       IN      A       192.168.254.6
www       IN      A       192.168.254.7

🔄 Forwarders

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Forwarders allow DNS queries to be sent to another DNS server for resolution. This can improve performance and ensure queries are resolved by reliable external DNS servers.

Configure forwarders inside the options block in the named.conf file:

options {
    forwarders {
        8.8.8.8;  // Google Public DNS
        1.1.1.1;  // Cloudflare DNS
    };
};

🔒 Access Control

Warning

Use Access Control Lists (ACLs) to manage which hosts or networks can query or transfer zones. Improper configurations can expose your DNS to unauthorized access.

Example ACL configuration:

acl "trusted" {
    192.168.1.0/24;
    localhost;
};
 
options {
    allow-query { any; };
    allow-transfer { "trusted"; };
};

In this example, only hosts within the “trusted” ACL (like the 192.168.1.0/24 network) are allowed to transfer zones, and any host can query.

🔄 Dynamic Updates

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Dynamic updates allow real-time modification of DNS records without the need to manually edit zone files. You can secure dynamic updates using TSIG (Transaction SIGnature) keys.

🛠️ Generate TSIG Key

To generate a TSIG key:

tsig-keygen -a hmac-sha256

🔑 Configure TSIG for Dynamic Updates

zone "example.com" {
    type master;
    file "example.com.zone";
    allow-update { key "tsig-key"; };
};

📚 Further Information

For more detailed examples and use cases, refer to the following:

🔁 Related Resources

Info

🏷️ Tags

bind9
dns
dnssec
dynamic-updates
zone-file
access-control
dns-server
network-security
dns-forwarders

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