Runlevels

Global switch of the system operating mode. More...

Modules
	Runlevel enable masks
	Definitions used to implement runlevels.

Enumerations
enum	RunLevel { RunLevel_COUNT }
	System runlevel. More...

Functions
void	services_set_runlevel (RunLevel runlevel)
	Switch the system to a runlevel.

Detailed Description

Global switch of the system operating mode.

Roughly analogous to SysVinit runlevels. In each runlevel, a service controlled by the runlevel system is either enabled (operating normally) or disabled (suppressed, non-operational). The exact meaning of the enabled state is up to the service.

The enabled state acts like a circuit breaker for a light switch: with the breaker off, the light is off whatever the switch position; with it on, the switch decides. Many services let the switch be flipped while disabled, the change taking effect once enabled.

A controllable service provides a single service_set_enabled(bool) function that:

• is only called by the runlevel system,
• is idempotent,
• and expects the service to start disabled when initialized.

Starting disabled avoids an uninitialized, enabled, disabled sequence when booting into a runlevel where the service is off, and exercises the disabled to enabled path on every boot.

There is deliberately no services_get_runlevel(): code must not change behaviour based on the runlevel without being listed and controlled by services_set_runlevel(). Make the service controllable by the runlevel system instead.

Runlevels are defined in runlevel.def; see Runlevel enable masks for enable masks.

Enumeration Type Documentation

RunLevel

enum RunLevel

System runlevel.

One RunLevel_<name> value per entry of runlevel.def: RunLevel_BareMinimum, RunLevel_LowPower, RunLevel_Stationary, RunLevel_FirmwareUpdate and RunLevel_Normal.

Enumerator
RunLevel_COUNT	Number of runlevels.

Function Documentation

services_set_runlevel()

void services_set_runlevel

(

RunLevel

runlevel

)

Switch the system to a runlevel.

Enables or disables every runlevel-controlled service according to its enable mask.

Parameters

runlevel

Runlevel to switch to.