rc-update:tldr:10dfe

The command "sudo rc-update add ${service_name} ${runlevel}" is used in Unix-like operating systems, particularly in Gentoo-based distributions, to add a service to a specific runlevel.

Here is the breakdown of the command:

• "sudo" is a command that allows a user with administrative privileges (usually the root user) to execute commands as another user, often required for system-related actions.
• "rc-update" is a command utilized in Gentoo-based systems to manage the runlevels and services.
• "add" is an argument specifying that we want to add a service to a runlevel.
• "${service_name}" is a placeholder for the name of the service that you want to add to a runlevel. You need to replace "${service_name}" with the actual name of the service (e.g., apache2, ssh).
• "${runlevel}" is another placeholder representing the runlevel to which you want to add the service. Runlevels categorize the services that need to be started or stopped during the system startup or shutdown process. Common runlevels include "default," "boot," or numeric runlevels like "3" or "5."

Example usage:

If you wanted to add the "apache2" service to the default runlevel, you would replace "${service_name}" with "apache2" and "${runlevel}" with "default." The command would then be:

sudo rc-update add apache2 default

This will ensure that the "apache2" service starts automatically when the system boots up into the default runlevel.