What is the purpose of the 'systemctl mask' command?

The 'systemctl mask' command is used with the specific purpose of preventing a service from being started, whether manually or automatically. By masking a service, you create a symbolic link to /dev/null for the service's unit file, effectively disabling it. This means that any attempt to start the service will fail, because the service is no longer accessible in the usual location where systemd looks for it.

This command is particularly useful in scenarios where you want to ensure that a certain service cannot be accidentally started or if you need to resolve conflicts with other services that might be dependent on it. Masking a service is more severe than simply stopping or disabling it, as it ensures complete removal of the service’s functionality until it is unmasked. Understanding this command is crucial for effective system management and control when working with systemd and services on RHEL systems.