What command stops all running services and powers down the system?

The option that accurately stops all running services and powers down the system is "shutdown -h now." This command is a standard method in Linux for shutting down the system immediately. The "shutdown" command is versatile; the "-h" flag specifies that the system should halt after terminating all running services, and "now" indicates that this action should be taken immediately.

Using "systemctl poweroff" does indeed power off the system, but it is more appropriate for clean shutdown processes rather than explicitly halting all services beforehand. While it will typically stop processes before shutting down, it does not directly convey the intent to halt all services before the power-off command is executed.

The command "systemctl halt" stops the system without powering off, which is not the requirement here. "service stop all" is not a standard command syntax in systemd-based systems and would not be recognized as is.

Therefore, "shutdown -h now" is the command that explicitly encompasses stopping all running services followed by powering down the system, making it the most appropriate choice.