Configure DNS on Linux for Reliable Domain Resolution

Himanshu Joshi Knowledgebase

Configure DNS to ensure smooth internet functionality by translating human-readable domain names (like www.example.com) into IP addresses that computers can understand. DNS is a critical component of networking and is essential for accessing websites and online services. Configuring DNS on Linux allows you to manage how domain names are resolved on your system, whether you’re setting up a DNS server or configuring your system to use specific DNS resolvers.

Configure DNS on Linux

In this guide, we will walk you through how to configure DNS on a Linux server, including setting up a local DNS server and configuring DNS settings for clients.

Prerequisites

Before configuring DNS on your Linux system, ensure the following:

  • Linux Distribution: DNS can be configured on most Linux distributions, such as Ubuntu, CentOS, Debian, and RHEL.
  • Root Access: You will need root or sudo access to install and configure DNS settings on your system.
  • Basic Knowledge of DNS: It’s helpful to have a basic understanding of how DNS works, including terms like resolver, zone, and record types (A, CNAME, MX, etc.).

Configure DNS on Linux

Configure DNS on Linux to manage domain name resolution and ensure smooth network communication. Proper DNS setup translates domain names into IP addresses, allowing your server to connect to websites, services, and other systems efficiently.

Step 1: Configure DNS Resolver

If you’re configuring DNS for a client machine or a server that uses an external DNS resolver, you’ll need to edit the DNS settings in the system configuration files.

Configure DNS on Ubuntu/Debian

  • Edit the resolv.conf file

The resolv.conf file contains the DNS servers that the system will use to resolve domain names. To configure DNS on a system running Ubuntu or Debian, edit this file:

sudo nano /etc/resolv.conf
  • Add DNS Server Entries

Add your desired DNS servers (you can use Google’s public DNS or Cloudflare’s DNS, for example):

nameserver 8.8.8.8        # Google's public DNS
nameserver 8.8.4.4        # Google's public DNS (secondary)

Alternatively, use Cloudflare’s public DNS:

nameserver 1.1.1.1        # Cloudflare's public DNS
nameserver 1.0.0.1        # Cloudflare's secondary DNS
  • Save and Exit

Save the file and exit the editor (CTRL + O to save and CTRL + X to exit for nano).

  • Restart Network Service

Restart the network service to apply the changes:

sudo systemctl restart networking

This will make the changes effective.

Configure DNS on CentOS/RHEL

  • Edit the resolv.conf file

For CentOS or RHEL, the process is similar. Edit the resolv.conf file:

sudo nano /etc/resolv.conf
  • Add DNS Server Entries

Add the nameserver lines for your desired DNS servers:

nameserver 8.8.8.8        # Google's public DNS
nameserver 8.8.4.4        # Google's secondary DNS
  • Save and Exit

Save and close the file (CTRL + O, CTRL + X for nano).

  • Restart Network Service

Restart the network service to apply the changes:

sudo systemctl restart network

Step 2: Set Up a Local DNS Server

If you want to set up a local DNS server to handle domain name resolution on your network, you can use BIND9 (Berkeley Internet Name Domain), which is one of the most widely used DNS servers on Linux systems.

Install BIND9

  • Install BIND9 on Ubuntu/Debian

To install BIND9 on an Ubuntu or Debian-based system, use the following commands:

sudo apt update
sudo apt install bind9 bind9utils bind9-doc dnsutils
  • Install BIND9 on CentOS/RHEL

On CentOS or RHEL, install BIND9 with the following:

sudo yum install bind bind-utils
  • Enable and Start BIND9 Service

After installation, enable and start the BIND9 service:

sudo systemctl enable bind9 sudo systemctl start bind9

For CentOS/RHEL:

sudo systemctl enable named sudo systemctl start named

Configure BIND9 for Local DNS Resolution

  • Edit the BIND9 Configuration File

The main configuration file for BIND9 is located at /etc/bind/named.conf. Open it for editing:

sudo nano /etc/bind/named.conf.options
  • Configure Forwarders (Optional)

Add external DNS servers to be used as forwarders. This allows your local DNS server to forward queries it can’t resolve to an upstream DNS server, such as Google’s public DNS:

forwarders { 8.8.8.8; # Google's DNS 8.8.4.4; # Google's secondary DNS };

This ensures that any queries your local DNS server cannot resolve will be forwarded to the specified DNS servers.

  • Allow Queries from Local Network

In the named.conf.local file (or within the named.conf.options file), add a allow-query directive to allow queries from your local network:

allow-query { 192.168.1.0/24; }; # Allow from local network (adjust IP range)

This restricts DNS queries to devices within your local network. Replace 192.168.1.0/24 with the appropriate IP range for your network.

  • Configure Local Zone File

If you want your DNS server to handle local domain names, you need to configure zone files. For example, to handle localdomain.local as a local domain, create the zone file:

sudo nano /etc/bind/db.localdomain.local

Example zone file:

$TTL    86400
@       IN      SOA     ns1.localdomain.local. admin.localdomain.local. (
                          2023071101 ; Serial
                          3600       ; Refresh
                          1800       ; Retry
                          1209600    ; Expire
                          86400 )    ; Minimum TTL

        IN      NS      ns1.localdomain.local.
ns1     IN      A       192.168.1.10
        IN      A       192.168.1.11
  • Restart BIND9 Service

After making changes to the configuration, restart the BIND9 service to apply them:

sudo systemctl restart bind9 # For Ubuntu/Debian sudo systemctl restart named # For CentOS/RHEL

Step 3: Test DNS Resolution

Once the DNS server is configured, you can test if it’s working correctly.

  • Test DNS Resolution with dig

Use the dig command to test DNS resolution: bashCopydig @localhost example.com If you’ve set up a local domain, try:

dig @localhost localdomain.local
  • Test Forwarding DNS

You can also check if DNS queries are being forwarded to the correct DNS servers by using dig:

dig @your_local_dns_server google.com

Step 4: Set Up DNS Caching

DNS caching improves the speed of DNS lookups by storing resolved domain names for a certain period of time.

  • Install dnsmasq for DNS Caching

On Ubuntu/Debian:

sudo apt install dnsmasq

On CentOS/RHEL:

sudo yum install dnsmasq
  • Configure dnsmasq

Edit the dnsmasq configuration file:

sudo nano /etc/dnsmasq.conf

Set it up to use your local DNS server or upstream DNS servers:

server=127.0.0.1 # Use local DNS server
  • Start and Enable dnsmasq

Enable and start the dnsmasq service:

sudo systemctl start dnsmasq sudo systemctl enable dnsmasq

Conclusion

In this article, we’ve covered how to configure DNS on Linux, including configuring the DNS resolver for a client machine, setting up a local DNS server using BIND9, and optionally implementing DNS caching with dnsmasq. DNS is a crucial part of networking, and having proper DNS configuration ensures faster domain resolution and enhances the security and reliability of your network.

By following this guide, you can efficiently set up DNS resolution on your Linux system, whether you’re managing a small network, hosting your local domains, or configuring a full DNS server.

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