Adding a DNS Server

Photon OS uses systemd-resolved to resolve domain names, IP addresses, and network names for local applications. The systemd-resolved daemon automatically creates and maintains the /etc/resolv.conf file, into which systemd-resolved places the IP address of the DNS server. You must not modify the /etc/resolv.conf file.

Note: If you want to implement a local resolver like bind instead of systemd-resolved, stop the systemd-resolved service and disable it.

If you open the default /etc/resolv.conf file after you deploy Photon OS, it looks like this:

root@photon-rc [ ~ ]# cat /etc/resolv.conf
# This file is managed by systemd-resolved(8). Do not edit.
#
# Third party programs must not access this file directly, but
# only through the symlink at /etc/resolv.conf. To manage
# resolv.conf(5) in a different way, replace the symlink by a
# static file or a different symlink.

nameserver 198.51.100.2

To add a DNS server, insert a DNS key into the Network section of the static network configuration file, for example, /etc/systemd/network/10-eth0-static.network and set it to the IP address of your DNS server:

[Match]
Name=e*

[Network]
Address=198.51.0.2/24
Gateway=198.51.0.1
DNS=198.51.0.1

Note: To apply the changes made to /etc/systemd/network/*.network files, perform the following:

• Restart systemd-networkd and systemd-resolved services by running the following commands:

  • systemctl restart systemd-networkd
  • systemctl restart systemd-resolved

• Or you can reload and reconfigure the settings by running the following commands: networkctl reload networkctl reconfigure *interface_name/index_number*

Note: The advantage of using reload and reconfigure is that the settings of other interfaces are not disturbed and only the settings of the specific interface are reloaded and reconfigured.

If your machine is working with DHCP, you can add a DNS server by modifying the /etc/systemd/resolved.conf--a method.

For more information, see https://www.freedesktop.org/software/systemd/man/resolved.conf.html.

You can optionally activate the local DNS stub resolver of systemd-resolved by adding dns and resolve to the /etc/nsswitch.conf file. To do so, make a backup copy of the /etc/nsswitch.conf file and then execute the following command as root:

sed -i 's/^hosts.*$/hosts: files resolve dns/' /etc/nsswitch.conf

For more information about the systemd-resolved service, see https://www.freedesktop.org/software/systemd/man/systemd-resolved.service.html.