The following shows how to create an on-off switch using PreferenceLoader for lighttpd.

• plutil - can be installed via Cydia
• lighttpd - can be installed via Cydia

                     /Library/PreferenceLoader/Preferences/net.lightysettings.plist
                     <string>PSSwitchCell</string>
                     <string>lightyEnabled</string>
                     <string>net.lighttpd</string> +------>>------+
                     <key>key</key>                               |
                    +<string>lightyEnabled</string> +----->>------+
                    v                                             |
  +------+----------|---+                                         |
  |      |         _+_  |                                         |
  |      | Enable [_|_] |                                         |
  +------+              |                                   write |
  | Ext  |              |                                         |
  +------+              |                                         |
  |      |              |                                         |
  |      |              |                                         |
  +------+--------------+                                         |
                                       +--------------------------+
                                       |                                 read
         /private/var/mobile/Library/Preferences/net.lighttpd.plist +----->>-----------*
                                       |                                               |
                                       |                       run                     |
                               launchd v monitor +-------------->>-----+ /etc/scripts/lighttpd_manager.sh
                                       |                                               +
                                       |                                              / \
                                       |                                             /   \
                  /Library/LaunchDaemons/net.lighttpd.plist                         /     \
                                                                               lighttpd  lighttpd
                                                                                  on       off

PreferenceLoader stores all Settings plists in:

/Library/PreferenceLoader/Preferences

Every item on the Settings pane filed under Extensions on a jailbroken device can reference a settings plist in /Library/PreferenceLoader/Preferences:

lightySettings.plist

<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>title</key>
	<string>Lighttpd Settings</string>
	<key>entry</key>
	<dict>
		<key>cell</key>
		<string>PSLinkCell</string>
		<key>label</key>
		<string>Lighttpd Settings</string>
		<key>icon</key>
		<string>LighttpdSettings.png</string>
	</dict>
	<key>items</key>
	<array>
		<dict>
                        <key>cell</key>
                        <string>PSSwitchCell</string>
                        <key>default</key>
                        <true/>
                        <key>defaults</key>
                        <string>net.lighttpd</string>
                        <key>key</key>
                        <string>lightyEnabled</string>
                        <key>label</key>
                        <string>Enable</string>
		</dict>
		<dict>
			<key>cell</key>
			<string>PSGroupCell</string>
			<key>footerText</key>
			<string>Lighttpd Switch (c) 2012 Wizardry and Steamworks.</string>
		</dict>
	</array>
</dict>
</plist>

The settings plist is located in:

/private/var/mobile/Library/Preferences

Whenever the example button above is flicked to on or off, we can see the setting in /private/var/mobile/Library/Preferences/net.lighttpd using plutil:

{
    lightyEnabled = 1;
}

Two icons are used:

• One large icon named LighttpdSettings@2x.png of size 55x58.

• One small icon named LighttpdSettings.png of size 28x29.

and must be uploaded in the same folder as LighttpdSettings.plist under /Library/PreferenceLoader/Preferences.

Then, using a launchd plist placed in /Library/LaunchDaemons/ we can execute a shell script whenever that setting changes:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>Label</key>
	<string>net.lighttpd</string>
	<key>LowPriorityIO</key>
	<true/>
	<key>ProgramArguments</key>
	<array>
		<string>/etc/scripts/lighttpd_launcher.sh</string>
	</array>
        <key>RunAtLoad</key>
	<true/>
        <key>WatchPaths</key>
	<array>
		<string>/private/var/mobile/Library/Preferences/net.lighttpd.plist</string>
	</array>
</dict>
</plist>

The underlying trick are the launchd directives:

        <key>WatchPaths</key>
	<array>
		<string>/private/var/mobile/Library/Preferences/net.lighttpd.plist</string>
	</array>

which make launchd monitor the /private/var/mobile/Library/Preferences/net.lighttpd.plist file for changes.

Then we add the lighttpd_manager.sh bash script in /etc/scripts/ containing:

lighttpd_manager.sh

#!/bin/bash
# Copyright (C) Wizardry and Steamworks.
#
#  Licensed to Wizardry and Steamworks under
# the GPLv3 GNU License which can be found at:
#    http://www.gnu.org/licenses/gpl.html
#
 
STATUS=`ps -ax | grep '[l]ighttpd' | awk '{ print $1 }'`
SETTING=`plutil -key lightyEnabled /private/var/mobile/Library/Preferences/net.lighttpd.plist`
 
if [ $SETTING -eq 0 ]; then
  kill -s TERM $STATUS
else
  lighttpd-angel -f /etc/lighttpd.conf
fi

which will make sure that the daemon is launched and killed once the button is flicked on the Settings pane.