Runlevel editor

# Runlevel editor library

documentation for developers

If you need activate or de-activate services from your yast2 package, use module `Service`. It is a replacement for the old client `runlevel_adjust` that you should have been using till now. You may also use it to obtain information about services. Following functions are self-containing. You do not need to run Service::Read if you want to use any of them.

## Enabling/disabling service

`boolean Service::Adjust (string name, string action);`
Does some operation with init script. `name` is the name of the init script. `action` is one of: `"enable", "disable", "default"`.

- `"enable"` enables service, which means that if service is not set to run in any runlevel, it will set it to run in default runlevels. Otherwise it will not touch the service. Use it when you want the service to run, because it preserves user-defined state. If user sets service to run in some non-default runlevels, this will not destroy her own settings.
- `"disable"` disables service, which means that it sets it not to run in any runlevel.
- `"default"` sets service to run in its default runlevels, which are the runlevels listed in init script comment, fiels Default-Start.

`"enable"` and `"disable"` take no action when init script links are OK, but `"default"` runs always insserv.
example: `Service::Adjust ("cups", "disable");`

## Specifying runlevels for service

`boolean Service::Finetune (string name, list rl);`
Sets service to run in list `rl`. `rl` is list of strings.
example: `Service::Finetune ("cups", [ "5" ]);`
example: `Service::Finetune ("cups", [ "S", "3", "5" ]);`

## Init script actions

`integer RunInitScript (string name, string param);`
Runs init script `name` with parameter `param`. Returns init scripts exit value. I do not think it is worth to import module `Service` only because of this one function when you may simply call `SCR::Execute (.target.bash, ...)` with the same result. But if you use Service for something else, this function may increase readability of the code.
example: `RunInitScript ("cups", "restart");`

## Service info

`integer Service::Status (string name)
map Service::Info (string name)
map Service::FullInfo (string name)`
`Service::Status` tells whether service runs. It calls init script status and returns exit value.
`Service::Info` returns information about service. The map contains:

    $[ "defstart" : [ ... ], // list of strings
       "defstop"  : [ ... ], // list of default runlevels

       "start"    : [ ... ], // list of strings
       "stop"     : [ ... ], // list of real runlevels

       "reqstart" : [ ... ], // list of strings
       "reqstop"  : [ ... ], // prerequisites

       "description": string,// description
    ]

Values "def{start|stop}", "req{start|stop}" and "description" are taken from init script comments. "start" and "stop" are taken from links. `Service::FullInfo` combines info from `Service::Info` and `Service::Status` into one map. It adds key `"started"` with integeral value of `script status`. Service is enabled if `"start"` is not empty.

## Is service enabled?

`boolean Service::Enabled (string name)`
Returns true if service is set to run in any runlevel. False otherwise.

## Example of usage

    import "Service";

    boolean Read () ``{
    	if (0 != Service::RunInitScript ("foo", "restart"))
    	{
    		y2error ("Can not start service");
    		return false;
    	}
    	// ... your code ...
    }

    boolean Write () ``{
    	// ... write settings ...

    	// set service to correct state
    	if (start_it)
    	{
    		// enable service
    		Service::Adjust ("foo", "enable");
    		// reload changed settings
    		Service::RunInitScript ("foo", "reload");
    	}
    	else
    	{
    		// disable service
    		Service::Adjust ("foo", "disable");
    		// and stop it
    		Service::RunInitScript ("foo", "stop");
    	}
    }

## What should you know?

It has sense to run some services only in case that some other service runs. Now the only case known to me is `portmap` that is needed by NFS, NIS and others. Runlevel UI cares about this case. But if you use functions like `Service::Adjust`, you must take care about these dependencies yourself. If you know about other dependencies, let me know, I will implement them in UI.
Just for your info: Runleve UI warns user who wants to stop service `xdm`. If you know about another cases where it is wise idea to warn user, please let me know...

## Autogenerated documentation

Can be found here.

Petr Blahos pblahos@suse.cz