What is the effect of the 'systemctl disable' command on a service?

The 'systemctl disable' command plays a critical role in managing system services in a Linux environment that uses systemd for service management. When this command is executed on a specific service, it removes the symbolic links in the system's default target that point to the service unit file, thereby preventing the service from starting automatically during the boot process.

This command is particularly useful for users who want to optimize their system startup times by preventing certain services that are not necessary from running at boot. By disabling a service, it does not impact the current state of the service; that is, if the service is already running, it will continue to run until explicitly stopped or the system is shut down.

In contrast, other options highlight different functionalities: stopping a service immediately is performed with the 'systemctl stop' command; allowing a service to start on boot is managed with 'systemctl enable'; and resetting a service's configuration does not pertain to the disable operation but involves different commands that specifically target configuration files. Therefore, the accurate understanding of the effect of 'systemctl disable' lies in its capacity to prevent a service from starting on system boot.