devilbox/docs/howto/dns/add-custom-dns-server-on-linux.rst

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Add custom DNS server on Linux

On Linux the DNS settings can be controlled by various different methods. Two of them are via Network Manager and systemd-resolved. Choose on of the methods depending on your local setup.

Table of Contents

local

Assumption

This tutorial is using 127.0.0.1 as the DNS server IP address, as it is the method to setup Auto DNS for your local Devilbox.

Non permanent solution

When you just want to try out to add a new DNS server without permanent settings, you should use this option.

Note

Non permanent means, the settings will be gone when your DHCP release will be renewed, reconnecting to the network, restarting the network service, logging out or rebooting your machine.

1. Open /etc/resolv.conf with root or sudo privileges with your favourite editor on your host operating sustem:

   host> sudo vi /etc/resolv.conf

2. Add your new nameserver directive above all existing nameserver directives:

   # Generated by NetworkManager
   search intranet
   nameserver 127.0.0.1
   nameserver 192.168.0.10

3. It will work instantly after saving the file

Network Manager

(This is a permanent solution and needs to be reverted when you don't need it anymore)

Edit /etc/dhcp/dhclient.conf with root or sudo privileges and add an instruction, which tells your local DHCP client that whenever any of your DNS servers are changed, you always want to have an additional entry, which is the one from the Devilbox (127.0.0.1).

Add the following line to to the very beginning to /etc/dhcp/dhclient.conf:

prepend domain-name-servers 127.0.0.1;

When you do that for the first time, you need to restart the network-manager service.

# Via service command
host> sudo service network-manager restart

# Or the systemd way
host> sudo systemctl restart network-manager

This will make sure that whenever your /etc/resolv.conf is deployed, you will have 127.0.0.1 as the first entry and also make use of any other DNS server which are deployed via the LAN's DHCP server.

If the Devilbox DNS server is not running, it does not affect the name resolution, because you will still have other entries in /etc/resolv.conf.

systemd-resolved

(This is a permanent solution and needs to be reverted when you don't need it anymore)

In case you are using systemd-resolved instead of NetworkManager, add the following line to the very beginning to /etc/resolv.conf.head:

nameserver 127.0.0.1

Prevent NetworkManager from modifying /etc/resolv.conf and leave everything to systemd-resolved by adding the following line under the [main] section of /etc/NetworkManager/NetworkManager.conf

dns=none

As a last step you will have to restart systemd-resolved.

host> sudo systemctl stop systemd-resolved
host> sudo systemctl start systemd-resolved

Once done, you can verify if the new DNS settings are effective:

host> systemd-resolve --status