To configure various services to start at different run levels, which command would you use?

The correct command for configuring various services to start at different run levels is "chkconfig." This command is designed for managing the system services on Linux systems that use SysVinit or similar init systems, allowing you to enable or disable services for specific run levels.

When you execute "chkconfig," you can specify which services should be automatically started or stopped when the system enters a particular run level. Each run level represents a specific state of the system, such as multi-user mode or single-user mode, and "chkconfig" provides a straightforward way to manage these configurations efficiently.

While "systemctl" is a command associated with systemd, particularly for managing services, it doesn't focus on run levels in the same way that "chkconfig" does. The "service control" option does not correspond to a valid command in standard Linux distributions, and "initctl" is specific to Upstart, which is not as commonly used as SysVinit or systemd today.

Understanding the tools used for service management across different init systems is crucial for configuring services effectively in a Linux environment.