Installation issue with port 53

Description

Linux reserves port 53 for DNS servers. Sometimes, the installation of High Availability Add-on (HAA) might fail because port 53 is already in use. This happens because HAA includes its own DNS server that needs port 53 open.

It is common for some Linux systems to have a DNS server running by default. To ensure a successful HAA installation, these servers need to be disabled. If you are using Ubuntu Linux, the DNS server is typically systemd-resolved, while on RHEL, it is likely to be dnsmasq.

The following sections provide instructions on how to deactivate the DNS servers.

Solution for Ubuntu Linux

To deactivate the systemd-resolved service, refer to the Redis documentation.

Solution for RHEL

To deactivate the dnsmasq service, follow these steps:

1. If the service is running, stop it:

    sudo systemctl stop dnsmasq

2. After stopping the service, you must disable it to prevent it from starting automatically on system reboot:

    sudo systemctl disable dnsmasq

3. Mask the service to prevent it from being started manually or by any other service:

    sudo systemctl mask dnsmasq

   When the service is masked, it cannot be started, even if another service or script tries to initiate it.

4. Verify that the service is no longer active and does not start on the following system reboot:

    sudo systemctl status dnsmasq